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09e6cef19c
linux/fs/btrfs/extent_io.c
Qu Wenruo 09e6cef19c btrfs: refactor alloc_extent_buffer() to allocate-then-attach method 
Currently alloc_extent_buffer() utilizes find_or_create_page() to
allocate one page a time for an extent buffer.

This method has the following disadvantages:

- find_or_create_page() is the legacy way of allocating new pages
  With the new folio infrastructure, find_or_create_page() is just
  redirected to filemap_get_folio().

- Lacks the way to support higher order (order >= 1) folios
  As we can not yet let filemap give us a higher order folio.

This patch would change the workflow by the following way:

		Old		   |		new
-----------------------------------+-------------------------------------
                                   | ret = btrfs_alloc_page_array();
for (i = 0; i < num_pages; i++) {  | for (i = 0; i < num_pages; i++) {
    p = find_or_create_page();     |     ret = filemap_add_folio();
    /* Attach page private */      |     /* Reuse page cache if needed */
    /* Reused eb if needed */      |
				   |     /* Attach page private and
				   |        reuse eb if needed */
				   | }

By this we split the page allocation and private attaching into two
parts, allowing future updates to each part more easily, and migrate to
folio interfaces (especially for possible higher order folios).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2023-12-15 23:01:04 +01:00

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// SPDX-License-Identifier: GPL-2.0
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/bio.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/page-flags.h>
#include <linux/sched/mm.h>
#include <linux/spinlock.h>
#include <linux/blkdev.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/prefetch.h>
#include <linux/fsverity.h>
#include "misc.h"
#include "extent_io.h"
#include "extent-io-tree.h"
#include "extent_map.h"
#include "ctree.h"
#include "btrfs_inode.h"
#include "bio.h"
#include "locking.h"
#include "rcu-string.h"
#include "backref.h"
#include "disk-io.h"
#include "subpage.h"
#include "zoned.h"
#include "block-group.h"
#include "compression.h"
#include "fs.h"
#include "accessors.h"
#include "file-item.h"
#include "file.h"
#include "dev-replace.h"
#include "super.h"
#include "transaction.h"
static struct kmem_cache *extent_buffer_cache;
#ifdef CONFIG_BTRFS_DEBUG
static inline void btrfs_leak_debug_add_eb(struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
unsigned long flags;
spin_lock_irqsave(&fs_info->eb_leak_lock, flags);
list_add(&eb->leak_list, &fs_info->allocated_ebs);
spin_unlock_irqrestore(&fs_info->eb_leak_lock, flags);
}
static inline void btrfs_leak_debug_del_eb(struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
unsigned long flags;
spin_lock_irqsave(&fs_info->eb_leak_lock, flags);
list_del(&eb->leak_list);
spin_unlock_irqrestore(&fs_info->eb_leak_lock, flags);
}
void btrfs_extent_buffer_leak_debug_check(struct btrfs_fs_info *fs_info)
{
struct extent_buffer *eb;
unsigned long flags;
/*
* If we didn't get into open_ctree our allocated_ebs will not be
* initialized, so just skip this.
*/
if (!fs_info->allocated_ebs.next)
return;
WARN_ON(!list_empty(&fs_info->allocated_ebs));
spin_lock_irqsave(&fs_info->eb_leak_lock, flags);
while (!list_empty(&fs_info->allocated_ebs)) {
eb = list_first_entry(&fs_info->allocated_ebs,
struct extent_buffer, leak_list);
pr_err(
"BTRFS: buffer leak start %llu len %lu refs %d bflags %lu owner %llu\n",
eb->start, eb->len, atomic_read(&eb->refs), eb->bflags,
btrfs_header_owner(eb));
list_del(&eb->leak_list);
kmem_cache_free(extent_buffer_cache, eb);
}
spin_unlock_irqrestore(&fs_info->eb_leak_lock, flags);
}
#else
#define btrfs_leak_debug_add_eb(eb) do {} while (0)
#define btrfs_leak_debug_del_eb(eb) do {} while (0)
#endif
/*
* Structure to record info about the bio being assembled, and other info like
* how many bytes are there before stripe/ordered extent boundary.
*/
struct btrfs_bio_ctrl {
struct btrfs_bio *bbio;
enum btrfs_compression_type compress_type;
u32 len_to_oe_boundary;
blk_opf_t opf;
btrfs_bio_end_io_t end_io_func;
struct writeback_control *wbc;
};
static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
{
struct btrfs_bio *bbio = bio_ctrl->bbio;
if (!bbio)
return;
/* Caller should ensure the bio has at least some range added */
ASSERT(bbio->bio.bi_iter.bi_size);
if (btrfs_op(&bbio->bio) == BTRFS_MAP_READ &&
bio_ctrl->compress_type != BTRFS_COMPRESS_NONE)
btrfs_submit_compressed_read(bbio);
else
btrfs_submit_bio(bbio, 0);
/* The bbio is owned by the end_io handler now */
bio_ctrl->bbio = NULL;
}
/*
* Submit or fail the current bio in the bio_ctrl structure.
*/
static void submit_write_bio(struct btrfs_bio_ctrl *bio_ctrl, int ret)
{
struct btrfs_bio *bbio = bio_ctrl->bbio;
if (!bbio)
return;
if (ret) {
ASSERT(ret < 0);
btrfs_bio_end_io(bbio, errno_to_blk_status(ret));
/* The bio is owned by the end_io handler now */
bio_ctrl->bbio = NULL;
} else {
submit_one_bio(bio_ctrl);
}
}
int __init extent_buffer_init_cachep(void)
{
extent_buffer_cache = kmem_cache_create("btrfs_extent_buffer",
sizeof(struct extent_buffer), 0,
SLAB_MEM_SPREAD, NULL);
if (!extent_buffer_cache)
return -ENOMEM;
return 0;
}
void __cold extent_buffer_free_cachep(void)
{
/*
* Make sure all delayed rcu free are flushed before we
* destroy caches.
*/
rcu_barrier();
kmem_cache_destroy(extent_buffer_cache);
}
void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
{
unsigned long index = start >> PAGE_SHIFT;
unsigned long end_index = end >> PAGE_SHIFT;
struct page *page;
while (index <= end_index) {
page = find_get_page(inode->i_mapping, index);
BUG_ON(!page); /* Pages should be in the extent_io_tree */
clear_page_dirty_for_io(page);
put_page(page);
index++;
}
}
static void process_one_page(struct btrfs_fs_info *fs_info,
struct page *page, struct page *locked_page,
unsigned long page_ops, u64 start, u64 end)
{
u32 len;
ASSERT(end + 1 - start != 0 && end + 1 - start < U32_MAX);
len = end + 1 - start;
if (page_ops & PAGE_SET_ORDERED)
btrfs_page_clamp_set_ordered(fs_info, page, start, len);
if (page_ops & PAGE_START_WRITEBACK) {
btrfs_page_clamp_clear_dirty(fs_info, page, start, len);
btrfs_page_clamp_set_writeback(fs_info, page, start, len);
}
if (page_ops & PAGE_END_WRITEBACK)
btrfs_page_clamp_clear_writeback(fs_info, page, start, len);
if (page != locked_page && (page_ops & PAGE_UNLOCK))
btrfs_page_end_writer_lock(fs_info, page, start, len);
}
static void __process_pages_contig(struct address_space *mapping,
struct page *locked_page, u64 start, u64 end,
unsigned long page_ops)
{
struct btrfs_fs_info *fs_info = btrfs_sb(mapping->host->i_sb);
pgoff_t start_index = start >> PAGE_SHIFT;
pgoff_t end_index = end >> PAGE_SHIFT;
pgoff_t index = start_index;
struct folio_batch fbatch;
int i;
folio_batch_init(&fbatch);
while (index <= end_index) {
int found_folios;
found_folios = filemap_get_folios_contig(mapping, &index,
end_index, &fbatch);
for (i = 0; i < found_folios; i++) {
struct folio *folio = fbatch.folios[i];
process_one_page(fs_info, &folio->page, locked_page,
page_ops, start, end);
}
folio_batch_release(&fbatch);
cond_resched();
}
}
static noinline void __unlock_for_delalloc(struct inode *inode,
struct page *locked_page,
u64 start, u64 end)
{
unsigned long index = start >> PAGE_SHIFT;
unsigned long end_index = end >> PAGE_SHIFT;
ASSERT(locked_page);
if (index == locked_page->index && end_index == index)
return;
__process_pages_contig(inode->i_mapping, locked_page, start, end,
PAGE_UNLOCK);
}
static noinline int lock_delalloc_pages(struct inode *inode,
struct page *locked_page,
u64 start,
u64 end)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct address_space *mapping = inode->i_mapping;
pgoff_t start_index = start >> PAGE_SHIFT;
pgoff_t end_index = end >> PAGE_SHIFT;
pgoff_t index = start_index;
u64 processed_end = start;
struct folio_batch fbatch;
if (index == locked_page->index && index == end_index)
return 0;
folio_batch_init(&fbatch);
while (index <= end_index) {
unsigned int found_folios, i;
found_folios = filemap_get_folios_contig(mapping, &index,
end_index, &fbatch);
if (found_folios == 0)
goto out;
for (i = 0; i < found_folios; i++) {
struct page *page = &fbatch.folios[i]->page;
u32 len = end + 1 - start;
if (page == locked_page)
continue;
if (btrfs_page_start_writer_lock(fs_info, page, start,
len))
goto out;
if (!PageDirty(page) || page->mapping != mapping) {
btrfs_page_end_writer_lock(fs_info, page, start,
len);
goto out;
}
processed_end = page_offset(page) + PAGE_SIZE - 1;
}
folio_batch_release(&fbatch);
cond_resched();
}
return 0;
out:
folio_batch_release(&fbatch);
if (processed_end > start)
__unlock_for_delalloc(inode, locked_page, start, processed_end);
return -EAGAIN;
}
/*
* Find and lock a contiguous range of bytes in the file marked as delalloc, no
* more than @max_bytes.
*
* @start: The original start bytenr to search.
* Will store the extent range start bytenr.
* @end: The original end bytenr of the search range
* Will store the extent range end bytenr.
*
* Return true if we find a delalloc range which starts inside the original
* range, and @start/@end will store the delalloc range start/end.
*
* Return false if we can't find any delalloc range which starts inside the
* original range, and @start/@end will be the non-delalloc range start/end.
*/
EXPORT_FOR_TESTS
noinline_for_stack bool find_lock_delalloc_range(struct inode *inode,
struct page *locked_page, u64 *start,
u64 *end)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
const u64 orig_start = *start;
const u64 orig_end = *end;
/* The sanity tests may not set a valid fs_info. */
u64 max_bytes = fs_info ? fs_info->max_extent_size : BTRFS_MAX_EXTENT_SIZE;
u64 delalloc_start;
u64 delalloc_end;
bool found;
struct extent_state *cached_state = NULL;
int ret;
int loops = 0;
/* Caller should pass a valid @end to indicate the search range end */
ASSERT(orig_end > orig_start);
/* The range should at least cover part of the page */
ASSERT(!(orig_start >= page_offset(locked_page) + PAGE_SIZE ||
orig_end <= page_offset(locked_page)));
again:
/* step one, find a bunch of delalloc bytes starting at start */
delalloc_start = *start;
delalloc_end = 0;
found = btrfs_find_delalloc_range(tree, &delalloc_start, &delalloc_end,
max_bytes, &cached_state);
if (!found || delalloc_end <= *start || delalloc_start > orig_end) {
*start = delalloc_start;
/* @delalloc_end can be -1, never go beyond @orig_end */
*end = min(delalloc_end, orig_end);
free_extent_state(cached_state);
return false;
}
/*
* start comes from the offset of locked_page. We have to lock
* pages in order, so we can't process delalloc bytes before
* locked_page
*/
if (delalloc_start < *start)
delalloc_start = *start;
/*
* make sure to limit the number of pages we try to lock down
*/
if (delalloc_end + 1 - delalloc_start > max_bytes)
delalloc_end = delalloc_start + max_bytes - 1;
/* step two, lock all the pages after the page that has start */
ret = lock_delalloc_pages(inode, locked_page,
delalloc_start, delalloc_end);
ASSERT(!ret || ret == -EAGAIN);
if (ret == -EAGAIN) {
/* some of the pages are gone, lets avoid looping by
* shortening the size of the delalloc range we're searching
*/
free_extent_state(cached_state);
cached_state = NULL;
if (!loops) {
max_bytes = PAGE_SIZE;
loops = 1;
goto again;
} else {
found = false;
goto out_failed;
}
}
/* step three, lock the state bits for the whole range */
lock_extent(tree, delalloc_start, delalloc_end, &cached_state);
/* then test to make sure it is all still delalloc */
ret = test_range_bit(tree, delalloc_start, delalloc_end,
EXTENT_DELALLOC, cached_state);
if (!ret) {
unlock_extent(tree, delalloc_start, delalloc_end,
&cached_state);
__unlock_for_delalloc(inode, locked_page,
delalloc_start, delalloc_end);
cond_resched();
goto again;
}
free_extent_state(cached_state);
*start = delalloc_start;
*end = delalloc_end;
out_failed:
return found;
}
void extent_clear_unlock_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
struct page *locked_page,
u32 clear_bits, unsigned long page_ops)
{
clear_extent_bit(&inode->io_tree, start, end, clear_bits, NULL);
__process_pages_contig(inode->vfs_inode.i_mapping, locked_page,
start, end, page_ops);
}
static bool btrfs_verify_page(struct page *page, u64 start)
{
if (!fsverity_active(page->mapping->host) ||
PageUptodate(page) ||
start >= i_size_read(page->mapping->host))
return true;
return fsverity_verify_page(page);
}
static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len)
{
struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
ASSERT(page_offset(page) <= start &&
start + len <= page_offset(page) + PAGE_SIZE);
if (uptodate && btrfs_verify_page(page, start))
btrfs_page_set_uptodate(fs_info, page, start, len);
else
btrfs_page_clear_uptodate(fs_info, page, start, len);
if (!btrfs_is_subpage(fs_info, page))
unlock_page(page);
else
btrfs_subpage_end_reader(fs_info, page, start, len);
}
/*
* after a writepage IO is done, we need to:
* clear the uptodate bits on error
* clear the writeback bits in the extent tree for this IO
* end_page_writeback if the page has no more pending IO
*
* Scheduling is not allowed, so the extent state tree is expected
* to have one and only one object corresponding to this IO.
*/
static void end_bio_extent_writepage(struct btrfs_bio *bbio)
{
struct bio *bio = &bbio->bio;
int error = blk_status_to_errno(bio->bi_status);
struct bio_vec *bvec;
struct bvec_iter_all iter_all;
ASSERT(!bio_flagged(bio, BIO_CLONED));
bio_for_each_segment_all(bvec, bio, iter_all) {
struct page *page = bvec->bv_page;
struct inode *inode = page->mapping->host;
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
const u32 sectorsize = fs_info->sectorsize;
u64 start = page_offset(page) + bvec->bv_offset;
u32 len = bvec->bv_len;
/* Our read/write should always be sector aligned. */
if (!IS_ALIGNED(bvec->bv_offset, sectorsize))
btrfs_err(fs_info,
"partial page write in btrfs with offset %u and length %u",
bvec->bv_offset, bvec->bv_len);
else if (!IS_ALIGNED(bvec->bv_len, sectorsize))
btrfs_info(fs_info,
"incomplete page write with offset %u and length %u",
bvec->bv_offset, bvec->bv_len);
btrfs_finish_ordered_extent(bbio->ordered, page, start, len, !error);
if (error)
mapping_set_error(page->mapping, error);
btrfs_page_clear_writeback(fs_info, page, start, len);
}
bio_put(bio);
}
/*
* Record previously processed extent range
*
* For endio_readpage_release_extent() to handle a full extent range, reducing
* the extent io operations.
*/
struct processed_extent {
struct btrfs_inode *inode;
/* Start of the range in @inode */
u64 start;
/* End of the range in @inode */
u64 end;
bool uptodate;
};
/*
* Try to release processed extent range
*
* May not release the extent range right now if the current range is
* contiguous to processed extent.
*
* Will release processed extent when any of @inode, @uptodate, the range is
* no longer contiguous to the processed range.
*
* Passing @inode == NULL will force processed extent to be released.
*/
static void endio_readpage_release_extent(struct processed_extent *processed,
struct btrfs_inode *inode, u64 start, u64 end,
bool uptodate)
{
struct extent_state *cached = NULL;
struct extent_io_tree *tree;
/* The first extent, initialize @processed */
if (!processed->inode)
goto update;
/*
* Contiguous to processed extent, just uptodate the end.
*
* Several things to notice:
*
* - bio can be merged as long as on-disk bytenr is contiguous
* This means we can have page belonging to other inodes, thus need to
* check if the inode still matches.
* - bvec can contain range beyond current page for multi-page bvec
* Thus we need to do processed->end + 1 >= start check
*/
if (processed->inode == inode && processed->uptodate == uptodate &&
processed->end + 1 >= start && end >= processed->end) {
processed->end = end;
return;
}
tree = &processed->inode->io_tree;
/*
* Now we don't have range contiguous to the processed range, release
* the processed range now.
*/
unlock_extent(tree, processed->start, processed->end, &cached);
update:
/* Update processed to current range */
processed->inode = inode;
processed->start = start;
processed->end = end;
processed->uptodate = uptodate;
}
static void begin_page_read(struct btrfs_fs_info *fs_info, struct page *page)
{
struct folio *folio = page_folio(page);
ASSERT(PageLocked(page));
if (!btrfs_is_subpage(fs_info, page))
return;
ASSERT(folio_test_private(folio));
btrfs_subpage_start_reader(fs_info, page, page_offset(page), PAGE_SIZE);
}
/*
* after a readpage IO is done, we need to:
* clear the uptodate bits on error
* set the uptodate bits if things worked
* set the page up to date if all extents in the tree are uptodate
* clear the lock bit in the extent tree
* unlock the page if there are no other extents locked for it
*
* Scheduling is not allowed, so the extent state tree is expected
* to have one and only one object corresponding to this IO.
*/
static void end_bio_extent_readpage(struct btrfs_bio *bbio)
{
struct bio *bio = &bbio->bio;
struct bio_vec *bvec;
struct processed_extent processed = { 0 };
/*
* The offset to the beginning of a bio, since one bio can never be
* larger than UINT_MAX, u32 here is enough.
*/
u32 bio_offset = 0;
struct bvec_iter_all iter_all;
ASSERT(!bio_flagged(bio, BIO_CLONED));
bio_for_each_segment_all(bvec, bio, iter_all) {
bool uptodate = !bio->bi_status;
struct page *page = bvec->bv_page;
struct inode *inode = page->mapping->host;
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
const u32 sectorsize = fs_info->sectorsize;
u64 start;
u64 end;
u32 len;
btrfs_debug(fs_info,
"end_bio_extent_readpage: bi_sector=%llu, err=%d, mirror=%u",
bio->bi_iter.bi_sector, bio->bi_status,
bbio->mirror_num);
/*
* We always issue full-sector reads, but if some block in a
* page fails to read, blk_update_request() will advance
* bv_offset and adjust bv_len to compensate. Print a warning
* for unaligned offsets, and an error if they don't add up to
* a full sector.
*/
if (!IS_ALIGNED(bvec->bv_offset, sectorsize))
btrfs_err(fs_info,
"partial page read in btrfs with offset %u and length %u",
bvec->bv_offset, bvec->bv_len);
else if (!IS_ALIGNED(bvec->bv_offset + bvec->bv_len,
sectorsize))
btrfs_info(fs_info,
"incomplete page read with offset %u and length %u",
bvec->bv_offset, bvec->bv_len);
start = page_offset(page) + bvec->bv_offset;
end = start + bvec->bv_len - 1;
len = bvec->bv_len;
if (likely(uptodate)) {
loff_t i_size = i_size_read(inode);
pgoff_t end_index = i_size >> PAGE_SHIFT;
/*
* Zero out the remaining part if this range straddles
* i_size.
*
* Here we should only zero the range inside the bvec,
* not touch anything else.
*
* NOTE: i_size is exclusive while end is inclusive.
*/
if (page->index == end_index && i_size <= end) {
u32 zero_start = max(offset_in_page(i_size),
offset_in_page(start));
zero_user_segment(page, zero_start,
offset_in_page(end) + 1);
}
}
/* Update page status and unlock. */
end_page_read(page, uptodate, start, len);
endio_readpage_release_extent(&processed, BTRFS_I(inode),
start, end, uptodate);
ASSERT(bio_offset + len > bio_offset);
bio_offset += len;
}
/* Release the last extent */
endio_readpage_release_extent(&processed, NULL, 0, 0, false);
bio_put(bio);
}
/*
* Populate every free slot in a provided array with pages.
*
* @nr_pages: number of pages to allocate
* @page_array: the array to fill with pages; any existing non-null entries in
* the array will be skipped
* @extra_gfp: the extra GFP flags for the allocation.
*
* Return: 0 if all pages were able to be allocated;
* -ENOMEM otherwise, the partially allocated pages would be freed and
* the array slots zeroed
*/
int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array,
gfp_t extra_gfp)
{
unsigned int allocated;
for (allocated = 0; allocated < nr_pages;) {
unsigned int last = allocated;
allocated = alloc_pages_bulk_array(GFP_NOFS | extra_gfp,
nr_pages, page_array);
if (allocated == nr_pages)
return 0;
/*
* During this iteration, no page could be allocated, even
* though alloc_pages_bulk_array() falls back to alloc_page()
* if it could not bulk-allocate. So we must be out of memory.
*/
if (allocated == last) {
for (int i = 0; i < allocated; i++) {
__free_page(page_array[i]);
page_array[i] = NULL;
}
return -ENOMEM;
}
memalloc_retry_wait(GFP_NOFS);
}
return 0;
}
static bool btrfs_bio_is_contig(struct btrfs_bio_ctrl *bio_ctrl,
struct page *page, u64 disk_bytenr,
unsigned int pg_offset)
{
struct bio *bio = &bio_ctrl->bbio->bio;
struct bio_vec *bvec = bio_last_bvec_all(bio);
const sector_t sector = disk_bytenr >> SECTOR_SHIFT;
if (bio_ctrl->compress_type != BTRFS_COMPRESS_NONE) {
/*
* For compression, all IO should have its logical bytenr set
* to the starting bytenr of the compressed extent.
*/
return bio->bi_iter.bi_sector == sector;
}
/*
* The contig check requires the following conditions to be met:
*
* 1) The pages are belonging to the same inode
* This is implied by the call chain.
*
* 2) The range has adjacent logical bytenr
*
* 3) The range has adjacent file offset
* This is required for the usage of btrfs_bio->file_offset.
*/
return bio_end_sector(bio) == sector &&
page_offset(bvec->bv_page) + bvec->bv_offset + bvec->bv_len ==
page_offset(page) + pg_offset;
}
static void alloc_new_bio(struct btrfs_inode *inode,
struct btrfs_bio_ctrl *bio_ctrl,
u64 disk_bytenr, u64 file_offset)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct btrfs_bio *bbio;
bbio = btrfs_bio_alloc(BIO_MAX_VECS, bio_ctrl->opf, fs_info,
bio_ctrl->end_io_func, NULL);
bbio->bio.bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
bbio->inode = inode;
bbio->file_offset = file_offset;
bio_ctrl->bbio = bbio;
bio_ctrl->len_to_oe_boundary = U32_MAX;
/* Limit data write bios to the ordered boundary. */
if (bio_ctrl->wbc) {
struct btrfs_ordered_extent *ordered;
ordered = btrfs_lookup_ordered_extent(inode, file_offset);
if (ordered) {
bio_ctrl->len_to_oe_boundary = min_t(u32, U32_MAX,
ordered->file_offset +
ordered->disk_num_bytes - file_offset);
bbio->ordered = ordered;
}
/*
* Pick the last added device to support cgroup writeback. For
* multi-device file systems this means blk-cgroup policies have
* to always be set on the last added/replaced device.
* This is a bit odd but has been like that for a long time.
*/
bio_set_dev(&bbio->bio, fs_info->fs_devices->latest_dev->bdev);
wbc_init_bio(bio_ctrl->wbc, &bbio->bio);
}
}
/*
* @disk_bytenr: logical bytenr where the write will be
* @page: page to add to the bio
* @size: portion of page that we want to write to
* @pg_offset: offset of the new bio or to check whether we are adding
* a contiguous page to the previous one
*
* The will either add the page into the existing @bio_ctrl->bbio, or allocate a
* new one in @bio_ctrl->bbio.
* The mirror number for this IO should already be initizlied in
* @bio_ctrl->mirror_num.
*/
static void submit_extent_page(struct btrfs_bio_ctrl *bio_ctrl,
u64 disk_bytenr, struct page *page,
size_t size, unsigned long pg_offset)
{
struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
ASSERT(pg_offset + size <= PAGE_SIZE);
ASSERT(bio_ctrl->end_io_func);
if (bio_ctrl->bbio &&
!btrfs_bio_is_contig(bio_ctrl, page, disk_bytenr, pg_offset))
submit_one_bio(bio_ctrl);
do {
u32 len = size;
/* Allocate new bio if needed */
if (!bio_ctrl->bbio) {
alloc_new_bio(inode, bio_ctrl, disk_bytenr,
page_offset(page) + pg_offset);
}
/* Cap to the current ordered extent boundary if there is one. */
if (len > bio_ctrl->len_to_oe_boundary) {
ASSERT(bio_ctrl->compress_type == BTRFS_COMPRESS_NONE);
ASSERT(is_data_inode(&inode->vfs_inode));
len = bio_ctrl->len_to_oe_boundary;
}
if (bio_add_page(&bio_ctrl->bbio->bio, page, len, pg_offset) != len) {
/* bio full: move on to a new one */
submit_one_bio(bio_ctrl);
continue;
}
if (bio_ctrl->wbc)
wbc_account_cgroup_owner(bio_ctrl->wbc, page, len);
size -= len;
pg_offset += len;
disk_bytenr += len;
/*
* len_to_oe_boundary defaults to U32_MAX, which isn't page or
* sector aligned. alloc_new_bio() then sets it to the end of
* our ordered extent for writes into zoned devices.
*
* When len_to_oe_boundary is tracking an ordered extent, we
* trust the ordered extent code to align things properly, and
* the check above to cap our write to the ordered extent
* boundary is correct.
*
* When len_to_oe_boundary is U32_MAX, the cap above would
* result in a 4095 byte IO for the last page right before
* we hit the bio limit of UINT_MAX. bio_add_page() has all
* the checks required to make sure we don't overflow the bio,
* and we should just ignore len_to_oe_boundary completely
* unless we're using it to track an ordered extent.
*
* It's pretty hard to make a bio sized U32_MAX, but it can
* happen when the page cache is able to feed us contiguous
* pages for large extents.
*/
if (bio_ctrl->len_to_oe_boundary != U32_MAX)
bio_ctrl->len_to_oe_boundary -= len;
/* Ordered extent boundary: move on to a new bio. */
if (bio_ctrl->len_to_oe_boundary == 0)
submit_one_bio(bio_ctrl);
} while (size);
}
static int attach_extent_buffer_page(struct extent_buffer *eb,
struct page *page,
struct btrfs_subpage *prealloc)
{
struct folio *folio = page_folio(page);
struct btrfs_fs_info *fs_info = eb->fs_info;
int ret = 0;
/*
* If the page is mapped to btree inode, we should hold the private
* lock to prevent race.
* For cloned or dummy extent buffers, their pages are not mapped and
* will not race with any other ebs.
*/
if (page->mapping)
lockdep_assert_held(&page->mapping->private_lock);
if (fs_info->nodesize >= PAGE_SIZE) {
if (!folio_test_private(folio))
folio_attach_private(folio, eb);
else
WARN_ON(folio_get_private(folio) != eb);
return 0;
}
/* Already mapped, just free prealloc */
if (folio_test_private(folio)) {
btrfs_free_subpage(prealloc);
return 0;
}
if (prealloc)
/* Has preallocated memory for subpage */
folio_attach_private(folio, prealloc);
else
/* Do new allocation to attach subpage */
ret = btrfs_attach_subpage(fs_info, page,
BTRFS_SUBPAGE_METADATA);
return ret;
}
int set_page_extent_mapped(struct page *page)
{
struct folio *folio = page_folio(page);
struct btrfs_fs_info *fs_info;
ASSERT(page->mapping);
if (folio_test_private(folio))
return 0;
fs_info = btrfs_sb(page->mapping->host->i_sb);
if (btrfs_is_subpage(fs_info, page))
return btrfs_attach_subpage(fs_info, page, BTRFS_SUBPAGE_DATA);
folio_attach_private(folio, (void *)EXTENT_FOLIO_PRIVATE);
return 0;
}
void clear_page_extent_mapped(struct page *page)
{
struct folio *folio = page_folio(page);
struct btrfs_fs_info *fs_info;
ASSERT(page->mapping);
if (!folio_test_private(folio))
return;
fs_info = btrfs_sb(page->mapping->host->i_sb);
if (btrfs_is_subpage(fs_info, page))
return btrfs_detach_subpage(fs_info, page);
folio_detach_private(folio);
}
static struct extent_map *
__get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,
u64 start, u64 len, struct extent_map **em_cached)
{
struct extent_map *em;
if (em_cached && *em_cached) {
em = *em_cached;
if (extent_map_in_tree(em) && start >= em->start &&
start < extent_map_end(em)) {
refcount_inc(&em->refs);
return em;
}
free_extent_map(em);
*em_cached = NULL;
}
em = btrfs_get_extent(BTRFS_I(inode), page, pg_offset, start, len);
if (em_cached && !IS_ERR(em)) {
BUG_ON(*em_cached);
refcount_inc(&em->refs);
*em_cached = em;
}
return em;
}
/*
* basic readpage implementation. Locked extent state structs are inserted
* into the tree that are removed when the IO is done (by the end_io
* handlers)
* XXX JDM: This needs looking at to ensure proper page locking
* return 0 on success, otherwise return error
*/
static int btrfs_do_readpage(struct page *page, struct extent_map **em_cached,
struct btrfs_bio_ctrl *bio_ctrl, u64 *prev_em_start)
{
struct inode *inode = page->mapping->host;
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
u64 start = page_offset(page);
const u64 end = start + PAGE_SIZE - 1;
u64 cur = start;
u64 extent_offset;
u64 last_byte = i_size_read(inode);
u64 block_start;
struct extent_map *em;
int ret = 0;
size_t pg_offset = 0;
size_t iosize;
size_t blocksize = inode->i_sb->s_blocksize;
struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
ret = set_page_extent_mapped(page);
if (ret < 0) {
unlock_extent(tree, start, end, NULL);
unlock_page(page);
return ret;
}
if (page->index == last_byte >> PAGE_SHIFT) {
size_t zero_offset = offset_in_page(last_byte);
if (zero_offset) {
iosize = PAGE_SIZE - zero_offset;
memzero_page(page, zero_offset, iosize);
}
}
bio_ctrl->end_io_func = end_bio_extent_readpage;
begin_page_read(fs_info, page);
while (cur <= end) {
enum btrfs_compression_type compress_type = BTRFS_COMPRESS_NONE;
bool force_bio_submit = false;
u64 disk_bytenr;
ASSERT(IS_ALIGNED(cur, fs_info->sectorsize));
if (cur >= last_byte) {
iosize = PAGE_SIZE - pg_offset;
memzero_page(page, pg_offset, iosize);
unlock_extent(tree, cur, cur + iosize - 1, NULL);
end_page_read(page, true, cur, iosize);
break;
}
em = __get_extent_map(inode, page, pg_offset, cur,
end - cur + 1, em_cached);
if (IS_ERR(em)) {
unlock_extent(tree, cur, end, NULL);
end_page_read(page, false, cur, end + 1 - cur);
return PTR_ERR(em);
}
extent_offset = cur - em->start;
BUG_ON(extent_map_end(em) <= cur);
BUG_ON(end < cur);
compress_type = extent_map_compression(em);
iosize = min(extent_map_end(em) - cur, end - cur + 1);
iosize = ALIGN(iosize, blocksize);
if (compress_type != BTRFS_COMPRESS_NONE)
disk_bytenr = em->block_start;
else
disk_bytenr = em->block_start + extent_offset;
block_start = em->block_start;
if (em->flags & EXTENT_FLAG_PREALLOC)
block_start = EXTENT_MAP_HOLE;
/*
* If we have a file range that points to a compressed extent
* and it's followed by a consecutive file range that points
* to the same compressed extent (possibly with a different
* offset and/or length, so it either points to the whole extent
* or only part of it), we must make sure we do not submit a
* single bio to populate the pages for the 2 ranges because
* this makes the compressed extent read zero out the pages
* belonging to the 2nd range. Imagine the following scenario:
*
* File layout
* [0 - 8K] [8K - 24K]
* | |
* | |
* points to extent X, points to extent X,
* offset 4K, length of 8K offset 0, length 16K
*
* [extent X, compressed length = 4K uncompressed length = 16K]
*
* If the bio to read the compressed extent covers both ranges,
* it will decompress extent X into the pages belonging to the
* first range and then it will stop, zeroing out the remaining
* pages that belong to the other range that points to extent X.
* So here we make sure we submit 2 bios, one for the first
* range and another one for the third range. Both will target
* the same physical extent from disk, but we can't currently
* make the compressed bio endio callback populate the pages
* for both ranges because each compressed bio is tightly
* coupled with a single extent map, and each range can have
* an extent map with a different offset value relative to the
* uncompressed data of our extent and different lengths. This
* is a corner case so we prioritize correctness over
* non-optimal behavior (submitting 2 bios for the same extent).
*/
if (compress_type != BTRFS_COMPRESS_NONE &&
prev_em_start && *prev_em_start != (u64)-1 &&
*prev_em_start != em->start)
force_bio_submit = true;
if (prev_em_start)
*prev_em_start = em->start;
free_extent_map(em);
em = NULL;
/* we've found a hole, just zero and go on */
if (block_start == EXTENT_MAP_HOLE) {
memzero_page(page, pg_offset, iosize);
unlock_extent(tree, cur, cur + iosize - 1, NULL);
end_page_read(page, true, cur, iosize);
cur = cur + iosize;
pg_offset += iosize;
continue;
}
/* the get_extent function already copied into the page */
if (block_start == EXTENT_MAP_INLINE) {
unlock_extent(tree, cur, cur + iosize - 1, NULL);
end_page_read(page, true, cur, iosize);
cur = cur + iosize;
pg_offset += iosize;
continue;
}
if (bio_ctrl->compress_type != compress_type) {
submit_one_bio(bio_ctrl);
bio_ctrl->compress_type = compress_type;
}
if (force_bio_submit)
submit_one_bio(bio_ctrl);
submit_extent_page(bio_ctrl, disk_bytenr, page, iosize,
pg_offset);
cur = cur + iosize;
pg_offset += iosize;
}
return 0;
}
int btrfs_read_folio(struct file *file, struct folio *folio)
{
struct page *page = &folio->page;
struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
u64 start = page_offset(page);
u64 end = start + PAGE_SIZE - 1;
struct btrfs_bio_ctrl bio_ctrl = { .opf = REQ_OP_READ };
int ret;
btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
ret = btrfs_do_readpage(page, NULL, &bio_ctrl, NULL);
/*
* If btrfs_do_readpage() failed we will want to submit the assembled
* bio to do the cleanup.
*/
submit_one_bio(&bio_ctrl);
return ret;
}
static inline void contiguous_readpages(struct page *pages[], int nr_pages,
u64 start, u64 end,
struct extent_map **em_cached,
struct btrfs_bio_ctrl *bio_ctrl,
u64 *prev_em_start)
{
struct btrfs_inode *inode = BTRFS_I(pages[0]->mapping->host);
int index;
btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
for (index = 0; index < nr_pages; index++) {
btrfs_do_readpage(pages[index], em_cached, bio_ctrl,
prev_em_start);
put_page(pages[index]);
}
}
/*
* helper for __extent_writepage, doing all of the delayed allocation setup.
*
* This returns 1 if btrfs_run_delalloc_range function did all the work required
* to write the page (copy into inline extent). In this case the IO has
* been started and the page is already unlocked.
*
* This returns 0 if all went well (page still locked)
* This returns < 0 if there were errors (page still locked)
*/
static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
struct page *page, struct writeback_control *wbc)
{
const u64 page_start = page_offset(page);
const u64 page_end = page_start + PAGE_SIZE - 1;
u64 delalloc_start = page_start;
u64 delalloc_end = page_end;
u64 delalloc_to_write = 0;
int ret = 0;
while (delalloc_start < page_end) {
delalloc_end = page_end;
if (!find_lock_delalloc_range(&inode->vfs_inode, page,
&delalloc_start, &delalloc_end)) {
delalloc_start = delalloc_end + 1;
continue;
}
ret = btrfs_run_delalloc_range(inode, page, delalloc_start,
delalloc_end, wbc);
if (ret < 0)
return ret;
delalloc_start = delalloc_end + 1;
}
/*
* delalloc_end is already one less than the total length, so
* we don't subtract one from PAGE_SIZE
*/
delalloc_to_write +=
DIV_ROUND_UP(delalloc_end + 1 - page_start, PAGE_SIZE);
/*
* If btrfs_run_dealloc_range() already started I/O and unlocked
* the pages, we just need to account for them here.
*/
if (ret == 1) {
wbc->nr_to_write -= delalloc_to_write;
return 1;
}
if (wbc->nr_to_write < delalloc_to_write) {
int thresh = 8192;
if (delalloc_to_write < thresh * 2)
thresh = delalloc_to_write;
wbc->nr_to_write = min_t(u64, delalloc_to_write,
thresh);
}
return 0;
}
/*
* Find the first byte we need to write.
*
* For subpage, one page can contain several sectors, and
* __extent_writepage_io() will just grab all extent maps in the page
* range and try to submit all non-inline/non-compressed extents.
*
* This is a big problem for subpage, we shouldn't re-submit already written
* data at all.
* This function will lookup subpage dirty bit to find which range we really
* need to submit.
*
* Return the next dirty range in [@start, @end).
* If no dirty range is found, @start will be page_offset(page) + PAGE_SIZE.
*/
static void find_next_dirty_byte(struct btrfs_fs_info *fs_info,
struct page *page, u64 *start, u64 *end)
{
struct folio *folio = page_folio(page);
struct btrfs_subpage *subpage = folio_get_private(folio);
struct btrfs_subpage_info *spi = fs_info->subpage_info;
u64 orig_start = *start;
/* Declare as unsigned long so we can use bitmap ops */
unsigned long flags;
int range_start_bit;
int range_end_bit;
/*
* For regular sector size == page size case, since one page only
* contains one sector, we return the page offset directly.
*/
if (!btrfs_is_subpage(fs_info, page)) {
*start = page_offset(page);
*end = page_offset(page) + PAGE_SIZE;
return;
}
range_start_bit = spi->dirty_offset +
(offset_in_page(orig_start) >> fs_info->sectorsize_bits);
/* We should have the page locked, but just in case */
spin_lock_irqsave(&subpage->lock, flags);
bitmap_next_set_region(subpage->bitmaps, &range_start_bit, &range_end_bit,
spi->dirty_offset + spi->bitmap_nr_bits);
spin_unlock_irqrestore(&subpage->lock, flags);
range_start_bit -= spi->dirty_offset;
range_end_bit -= spi->dirty_offset;
*start = page_offset(page) + range_start_bit * fs_info->sectorsize;
*end = page_offset(page) + range_end_bit * fs_info->sectorsize;
}
/*
* helper for __extent_writepage. This calls the writepage start hooks,
* and does the loop to map the page into extents and bios.
*
* We return 1 if the IO is started and the page is unlocked,
* 0 if all went well (page still locked)
* < 0 if there were errors (page still locked)
*/
static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode,
struct page *page,
struct btrfs_bio_ctrl *bio_ctrl,
loff_t i_size,
int *nr_ret)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
u64 cur = page_offset(page);
u64 end = cur + PAGE_SIZE - 1;
u64 extent_offset;
u64 block_start;
struct extent_map *em;
int ret = 0;
int nr = 0;
ret = btrfs_writepage_cow_fixup(page);
if (ret) {
/* Fixup worker will requeue */
redirty_page_for_writepage(bio_ctrl->wbc, page);
unlock_page(page);
return 1;
}
bio_ctrl->end_io_func = end_bio_extent_writepage;
while (cur <= end) {
u32 len = end - cur + 1;
u64 disk_bytenr;
u64 em_end;
u64 dirty_range_start = cur;
u64 dirty_range_end;
u32 iosize;
if (cur >= i_size) {
btrfs_mark_ordered_io_finished(inode, page, cur, len,
true);
/*
* This range is beyond i_size, thus we don't need to
* bother writing back.
* But we still need to clear the dirty subpage bit, or
* the next time the page gets dirtied, we will try to
* writeback the sectors with subpage dirty bits,
* causing writeback without ordered extent.
*/
btrfs_page_clear_dirty(fs_info, page, cur, len);
break;
}
find_next_dirty_byte(fs_info, page, &dirty_range_start,
&dirty_range_end);
if (cur < dirty_range_start) {
cur = dirty_range_start;
continue;
}
em = btrfs_get_extent(inode, NULL, 0, cur, len);
if (IS_ERR(em)) {
ret = PTR_ERR_OR_ZERO(em);
goto out_error;
}
extent_offset = cur - em->start;
em_end = extent_map_end(em);
ASSERT(cur <= em_end);
ASSERT(cur < end);
ASSERT(IS_ALIGNED(em->start, fs_info->sectorsize));
ASSERT(IS_ALIGNED(em->len, fs_info->sectorsize));
block_start = em->block_start;
disk_bytenr = em->block_start + extent_offset;
ASSERT(!extent_map_is_compressed(em));
ASSERT(block_start != EXTENT_MAP_HOLE);
ASSERT(block_start != EXTENT_MAP_INLINE);
/*
* Note that em_end from extent_map_end() and dirty_range_end from
* find_next_dirty_byte() are all exclusive
*/
iosize = min(min(em_end, end + 1), dirty_range_end) - cur;
free_extent_map(em);
em = NULL;
btrfs_set_range_writeback(inode, cur, cur + iosize - 1);
if (!PageWriteback(page)) {
btrfs_err(inode->root->fs_info,
"page %lu not writeback, cur %llu end %llu",
page->index, cur, end);
}
/*
* Although the PageDirty bit is cleared before entering this
* function, subpage dirty bit is not cleared.
* So clear subpage dirty bit here so next time we won't submit
* page for range already written to disk.
*/
btrfs_page_clear_dirty(fs_info, page, cur, iosize);
submit_extent_page(bio_ctrl, disk_bytenr, page, iosize,
cur - page_offset(page));
cur += iosize;
nr++;
}
btrfs_page_assert_not_dirty(fs_info, page);
*nr_ret = nr;
return 0;
out_error:
/*
* If we finish without problem, we should not only clear page dirty,
* but also empty subpage dirty bits
*/
*nr_ret = nr;
return ret;
}
/*
* the writepage semantics are similar to regular writepage. extent
* records are inserted to lock ranges in the tree, and as dirty areas
* are found, they are marked writeback. Then the lock bits are removed
* and the end_io handler clears the writeback ranges
*
* Return 0 if everything goes well.
* Return <0 for error.
*/
static int __extent_writepage(struct page *page, struct btrfs_bio_ctrl *bio_ctrl)
{
struct folio *folio = page_folio(page);
struct inode *inode = page->mapping->host;
const u64 page_start = page_offset(page);
int ret;
int nr = 0;
size_t pg_offset;
loff_t i_size = i_size_read(inode);
unsigned long end_index = i_size >> PAGE_SHIFT;
trace___extent_writepage(page, inode, bio_ctrl->wbc);
WARN_ON(!PageLocked(page));
pg_offset = offset_in_page(i_size);
if (page->index > end_index ||
(page->index == end_index && !pg_offset)) {
folio_invalidate(folio, 0, folio_size(folio));
folio_unlock(folio);
return 0;
}
if (page->index == end_index)
memzero_page(page, pg_offset, PAGE_SIZE - pg_offset);
ret = set_page_extent_mapped(page);
if (ret < 0)
goto done;
ret = writepage_delalloc(BTRFS_I(inode), page, bio_ctrl->wbc);
if (ret == 1)
return 0;
if (ret)
goto done;
ret = __extent_writepage_io(BTRFS_I(inode), page, bio_ctrl, i_size, &nr);
if (ret == 1)
return 0;
bio_ctrl->wbc->nr_to_write--;
done:
if (nr == 0) {
/* make sure the mapping tag for page dirty gets cleared */
set_page_writeback(page);
end_page_writeback(page);
}
if (ret) {
btrfs_mark_ordered_io_finished(BTRFS_I(inode), page, page_start,
PAGE_SIZE, !ret);
mapping_set_error(page->mapping, ret);
}
unlock_page(page);
ASSERT(ret <= 0);
return ret;
}
void wait_on_extent_buffer_writeback(struct extent_buffer *eb)
{
wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_WRITEBACK,
TASK_UNINTERRUPTIBLE);
}
/*
* Lock extent buffer status and pages for writeback.
*
* Return %false if the extent buffer doesn't need to be submitted (e.g. the
* extent buffer is not dirty)
* Return %true is the extent buffer is submitted to bio.
*/
static noinline_for_stack bool lock_extent_buffer_for_io(struct extent_buffer *eb,
struct writeback_control *wbc)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
bool ret = false;
btrfs_tree_lock(eb);
while (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
btrfs_tree_unlock(eb);
if (wbc->sync_mode != WB_SYNC_ALL)
return false;
wait_on_extent_buffer_writeback(eb);
btrfs_tree_lock(eb);
}
/*
* We need to do this to prevent races in people who check if the eb is
* under IO since we can end up having no IO bits set for a short period
* of time.
*/
spin_lock(&eb->refs_lock);
if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
spin_unlock(&eb->refs_lock);
btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
-eb->len,
fs_info->dirty_metadata_batch);
ret = true;
} else {
spin_unlock(&eb->refs_lock);
}
btrfs_tree_unlock(eb);
return ret;
}
static void set_btree_ioerr(struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
set_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);
/*
* A read may stumble upon this buffer later, make sure that it gets an
* error and knows there was an error.
*/
clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
/*
* We need to set the mapping with the io error as well because a write
* error will flip the file system readonly, and then syncfs() will
* return a 0 because we are readonly if we don't modify the err seq for
* the superblock.
*/
mapping_set_error(eb->fs_info->btree_inode->i_mapping, -EIO);
/*
* If writeback for a btree extent that doesn't belong to a log tree
* failed, increment the counter transaction->eb_write_errors.
* We do this because while the transaction is running and before it's
* committing (when we call filemap_fdata[write|wait]_range against
* the btree inode), we might have
* btree_inode->i_mapping->a_ops->writepages() called by the VM - if it
* returns an error or an error happens during writeback, when we're
* committing the transaction we wouldn't know about it, since the pages
* can be no longer dirty nor marked anymore for writeback (if a
* subsequent modification to the extent buffer didn't happen before the
* transaction commit), which makes filemap_fdata[write|wait]_range not
* able to find the pages tagged with SetPageError at transaction
* commit time. So if this happens we must abort the transaction,
* otherwise we commit a super block with btree roots that point to
* btree nodes/leafs whose content on disk is invalid - either garbage
* or the content of some node/leaf from a past generation that got
* cowed or deleted and is no longer valid.
*
* Note: setting AS_EIO/AS_ENOSPC in the btree inode's i_mapping would
* not be enough - we need to distinguish between log tree extents vs
* non-log tree extents, and the next filemap_fdatawait_range() call
* will catch and clear such errors in the mapping - and that call might
* be from a log sync and not from a transaction commit. Also, checking
* for the eb flag EXTENT_BUFFER_WRITE_ERR at transaction commit time is
* not done and would not be reliable - the eb might have been released
* from memory and reading it back again means that flag would not be
* set (since it's a runtime flag, not persisted on disk).
*
* Using the flags below in the btree inode also makes us achieve the
* goal of AS_EIO/AS_ENOSPC when writepages() returns success, started
* writeback for all dirty pages and before filemap_fdatawait_range()
* is called, the writeback for all dirty pages had already finished
* with errors - because we were not using AS_EIO/AS_ENOSPC,
* filemap_fdatawait_range() would return success, as it could not know
* that writeback errors happened (the pages were no longer tagged for
* writeback).
*/
switch (eb->log_index) {
case -1:
set_bit(BTRFS_FS_BTREE_ERR, &fs_info->flags);
break;
case 0:
set_bit(BTRFS_FS_LOG1_ERR, &fs_info->flags);
break;
case 1:
set_bit(BTRFS_FS_LOG2_ERR, &fs_info->flags);
break;
default:
BUG(); /* unexpected, logic error */
}
}
/*
* The endio specific version which won't touch any unsafe spinlock in endio
* context.
*/
static struct extent_buffer *find_extent_buffer_nolock(
struct btrfs_fs_info *fs_info, u64 start)
{
struct extent_buffer *eb;
rcu_read_lock();
eb = radix_tree_lookup(&fs_info->buffer_radix,
start >> fs_info->sectorsize_bits);
if (eb && atomic_inc_not_zero(&eb->refs)) {
rcu_read_unlock();
return eb;
}
rcu_read_unlock();
return NULL;
}
static void extent_buffer_write_end_io(struct btrfs_bio *bbio)
{
struct extent_buffer *eb = bbio->private;
struct btrfs_fs_info *fs_info = eb->fs_info;
bool uptodate = !bbio->bio.bi_status;
struct bvec_iter_all iter_all;
struct bio_vec *bvec;
u32 bio_offset = 0;
if (!uptodate)
set_btree_ioerr(eb);
bio_for_each_segment_all(bvec, &bbio->bio, iter_all) {
u64 start = eb->start + bio_offset;
struct page *page = bvec->bv_page;
u32 len = bvec->bv_len;
btrfs_page_clear_writeback(fs_info, page, start, len);
bio_offset += len;
}
clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
smp_mb__after_atomic();
wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK);
bio_put(&bbio->bio);
}
static void prepare_eb_write(struct extent_buffer *eb)
{
u32 nritems;
unsigned long start;
unsigned long end;
clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);
/* Set btree blocks beyond nritems with 0 to avoid stale content */
nritems = btrfs_header_nritems(eb);
if (btrfs_header_level(eb) > 0) {
end = btrfs_node_key_ptr_offset(eb, nritems);
memzero_extent_buffer(eb, end, eb->len - end);
} else {
/*
* Leaf:
* header 0 1 2 .. N ... data_N .. data_2 data_1 data_0
*/
start = btrfs_item_nr_offset(eb, nritems);
end = btrfs_item_nr_offset(eb, 0);
if (nritems == 0)
end += BTRFS_LEAF_DATA_SIZE(eb->fs_info);
else
end += btrfs_item_offset(eb, nritems - 1);
memzero_extent_buffer(eb, start, end - start);
}
}
static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
struct writeback_control *wbc)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
struct btrfs_bio *bbio;
prepare_eb_write(eb);
bbio = btrfs_bio_alloc(INLINE_EXTENT_BUFFER_PAGES,
REQ_OP_WRITE | REQ_META | wbc_to_write_flags(wbc),
eb->fs_info, extent_buffer_write_end_io, eb);
bbio->bio.bi_iter.bi_sector = eb->start >> SECTOR_SHIFT;
bio_set_dev(&bbio->bio, fs_info->fs_devices->latest_dev->bdev);
wbc_init_bio(wbc, &bbio->bio);
bbio->inode = BTRFS_I(eb->fs_info->btree_inode);
bbio->file_offset = eb->start;
if (fs_info->nodesize < PAGE_SIZE) {
struct page *p = eb->pages[0];
lock_page(p);
btrfs_subpage_set_writeback(fs_info, p, eb->start, eb->len);
if (btrfs_subpage_clear_and_test_dirty(fs_info, p, eb->start,
eb->len)) {
clear_page_dirty_for_io(p);
wbc->nr_to_write--;
}
__bio_add_page(&bbio->bio, p, eb->len, eb->start - page_offset(p));
wbc_account_cgroup_owner(wbc, p, eb->len);
unlock_page(p);
} else {
for (int i = 0; i < num_extent_pages(eb); i++) {
struct page *p = eb->pages[i];
lock_page(p);
clear_page_dirty_for_io(p);
set_page_writeback(p);
__bio_add_page(&bbio->bio, p, PAGE_SIZE, 0);
wbc_account_cgroup_owner(wbc, p, PAGE_SIZE);
wbc->nr_to_write--;
unlock_page(p);
}
}
btrfs_submit_bio(bbio, 0);
}
/*
* Submit one subpage btree page.
*
* The main difference to submit_eb_page() is:
* - Page locking
* For subpage, we don't rely on page locking at all.
*
* - Flush write bio
* We only flush bio if we may be unable to fit current extent buffers into
* current bio.
*
* Return >=0 for the number of submitted extent buffers.
* Return <0 for fatal error.
*/
static int submit_eb_subpage(struct page *page, struct writeback_control *wbc)
{
struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
struct folio *folio = page_folio(page);
int submitted = 0;
u64 page_start = page_offset(page);
int bit_start = 0;
int sectors_per_node = fs_info->nodesize >> fs_info->sectorsize_bits;
/* Lock and write each dirty extent buffers in the range */
while (bit_start < fs_info->subpage_info->bitmap_nr_bits) {
struct btrfs_subpage *subpage = folio_get_private(folio);
struct extent_buffer *eb;
unsigned long flags;
u64 start;
/*
* Take private lock to ensure the subpage won't be detached
* in the meantime.
*/
spin_lock(&page->mapping->private_lock);
if (!folio_test_private(folio)) {
spin_unlock(&page->mapping->private_lock);
break;
}
spin_lock_irqsave(&subpage->lock, flags);
if (!test_bit(bit_start + fs_info->subpage_info->dirty_offset,
subpage->bitmaps)) {
spin_unlock_irqrestore(&subpage->lock, flags);
spin_unlock(&page->mapping->private_lock);
bit_start++;
continue;
}
start = page_start + bit_start * fs_info->sectorsize;
bit_start += sectors_per_node;
/*
* Here we just want to grab the eb without touching extra
* spin locks, so call find_extent_buffer_nolock().
*/
eb = find_extent_buffer_nolock(fs_info, start);
spin_unlock_irqrestore(&subpage->lock, flags);
spin_unlock(&page->mapping->private_lock);
/*
* The eb has already reached 0 refs thus find_extent_buffer()
* doesn't return it. We don't need to write back such eb
* anyway.
*/
if (!eb)
continue;
if (lock_extent_buffer_for_io(eb, wbc)) {
write_one_eb(eb, wbc);
submitted++;
}
free_extent_buffer(eb);
}
return submitted;
}
/*
* Submit all page(s) of one extent buffer.
*
* @page: the page of one extent buffer
* @eb_context: to determine if we need to submit this page, if current page
* belongs to this eb, we don't need to submit
*
* The caller should pass each page in their bytenr order, and here we use
* @eb_context to determine if we have submitted pages of one extent buffer.
*
* If we have, we just skip until we hit a new page that doesn't belong to
* current @eb_context.
*
* If not, we submit all the page(s) of the extent buffer.
*
* Return >0 if we have submitted the extent buffer successfully.
* Return 0 if we don't need to submit the page, as it's already submitted by
* previous call.
* Return <0 for fatal error.
*/
static int submit_eb_page(struct page *page, struct btrfs_eb_write_context *ctx)
{
struct writeback_control *wbc = ctx->wbc;
struct address_space *mapping = page->mapping;
struct folio *folio = page_folio(page);
struct extent_buffer *eb;
int ret;
if (!folio_test_private(folio))
return 0;
if (btrfs_sb(page->mapping->host->i_sb)->nodesize < PAGE_SIZE)
return submit_eb_subpage(page, wbc);
spin_lock(&mapping->private_lock);
if (!folio_test_private(folio)) {
spin_unlock(&mapping->private_lock);
return 0;
}
eb = folio_get_private(folio);
/*
* Shouldn't happen and normally this would be a BUG_ON but no point
* crashing the machine for something we can survive anyway.
*/
if (WARN_ON(!eb)) {
spin_unlock(&mapping->private_lock);
return 0;
}
if (eb == ctx->eb) {
spin_unlock(&mapping->private_lock);
return 0;
}
ret = atomic_inc_not_zero(&eb->refs);
spin_unlock(&mapping->private_lock);
if (!ret)
return 0;
ctx->eb = eb;
ret = btrfs_check_meta_write_pointer(eb->fs_info, ctx);
if (ret) {
if (ret == -EBUSY)
ret = 0;
free_extent_buffer(eb);
return ret;
}
if (!lock_extent_buffer_for_io(eb, wbc)) {
free_extent_buffer(eb);
return 0;
}
/* Implies write in zoned mode. */
if (ctx->zoned_bg) {
/* Mark the last eb in the block group. */
btrfs_schedule_zone_finish_bg(ctx->zoned_bg, eb);
ctx->zoned_bg->meta_write_pointer += eb->len;
}
write_one_eb(eb, wbc);
free_extent_buffer(eb);
return 1;
}
int btree_write_cache_pages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct btrfs_eb_write_context ctx = { .wbc = wbc };
struct btrfs_fs_info *fs_info = BTRFS_I(mapping->host)->root->fs_info;
int ret = 0;
int done = 0;
int nr_to_write_done = 0;
struct folio_batch fbatch;
unsigned int nr_folios;
pgoff_t index;
pgoff_t end; /* Inclusive */
int scanned = 0;
xa_mark_t tag;
folio_batch_init(&fbatch);
if (wbc->range_cyclic) {
index = mapping->writeback_index; /* Start from prev offset */
end = -1;
/*
* Start from the beginning does not need to cycle over the
* range, mark it as scanned.
*/
scanned = (index == 0);
} else {
index = wbc->range_start >> PAGE_SHIFT;
end = wbc->range_end >> PAGE_SHIFT;
scanned = 1;
}
if (wbc->sync_mode == WB_SYNC_ALL)
tag = PAGECACHE_TAG_TOWRITE;
else
tag = PAGECACHE_TAG_DIRTY;
btrfs_zoned_meta_io_lock(fs_info);
retry:
if (wbc->sync_mode == WB_SYNC_ALL)
tag_pages_for_writeback(mapping, index, end);
while (!done && !nr_to_write_done && (index <= end) &&
(nr_folios = filemap_get_folios_tag(mapping, &index, end,
tag, &fbatch))) {
unsigned i;
for (i = 0; i < nr_folios; i++) {
struct folio *folio = fbatch.folios[i];
ret = submit_eb_page(&folio->page, &ctx);
if (ret == 0)
continue;
if (ret < 0) {
done = 1;
break;
}
/*
* the filesystem may choose to bump up nr_to_write.
* We have to make sure to honor the new nr_to_write
* at any time
*/
nr_to_write_done = wbc->nr_to_write <= 0;
}
folio_batch_release(&fbatch);
cond_resched();
}
if (!scanned && !done) {
/*
* We hit the last page and there is more work to be done: wrap
* back to the start of the file
*/
scanned = 1;
index = 0;
goto retry;
}
/*
* If something went wrong, don't allow any metadata write bio to be
* submitted.
*
* This would prevent use-after-free if we had dirty pages not
* cleaned up, which can still happen by fuzzed images.
*
* - Bad extent tree
* Allowing existing tree block to be allocated for other trees.
*
* - Log tree operations
* Exiting tree blocks get allocated to log tree, bumps its
* generation, then get cleaned in tree re-balance.
* Such tree block will not be written back, since it's clean,
* thus no WRITTEN flag set.
* And after log writes back, this tree block is not traced by
* any dirty extent_io_tree.
*
* - Offending tree block gets re-dirtied from its original owner
* Since it has bumped generation, no WRITTEN flag, it can be
* reused without COWing. This tree block will not be traced
* by btrfs_transaction::dirty_pages.
*
* Now such dirty tree block will not be cleaned by any dirty
* extent io tree. Thus we don't want to submit such wild eb
* if the fs already has error.
*
* We can get ret > 0 from submit_extent_page() indicating how many ebs
* were submitted. Reset it to 0 to avoid false alerts for the caller.
*/
if (ret > 0)
ret = 0;
if (!ret && BTRFS_FS_ERROR(fs_info))
ret = -EROFS;
if (ctx.zoned_bg)
btrfs_put_block_group(ctx.zoned_bg);
btrfs_zoned_meta_io_unlock(fs_info);
return ret;
}
/*
* Walk the list of dirty pages of the given address space and write all of them.
*
* @mapping: address space structure to write
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
* @bio_ctrl: holds context for the write, namely the bio
*
* If a page is already under I/O, write_cache_pages() skips it, even
* if it's dirty. This is desirable behaviour for memory-cleaning writeback,
* but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
* and msync() need to guarantee that all the data which was dirty at the time
* the call was made get new I/O started against them. If wbc->sync_mode is
* WB_SYNC_ALL then we were called for data integrity and we must wait for
* existing IO to complete.
*/
static int extent_write_cache_pages(struct address_space *mapping,
struct btrfs_bio_ctrl *bio_ctrl)
{
struct writeback_control *wbc = bio_ctrl->wbc;
struct inode *inode = mapping->host;
int ret = 0;
int done = 0;
int nr_to_write_done = 0;
struct folio_batch fbatch;
unsigned int nr_folios;
pgoff_t index;
pgoff_t end; /* Inclusive */
pgoff_t done_index;
int range_whole = 0;
int scanned = 0;
xa_mark_t tag;
/*
* We have to hold onto the inode so that ordered extents can do their
* work when the IO finishes. The alternative to this is failing to add
* an ordered extent if the igrab() fails there and that is a huge pain
* to deal with, so instead just hold onto the inode throughout the
* writepages operation. If it fails here we are freeing up the inode
* anyway and we'd rather not waste our time writing out stuff that is
* going to be truncated anyway.
*/
if (!igrab(inode))
return 0;
folio_batch_init(&fbatch);
if (wbc->range_cyclic) {
index = mapping->writeback_index; /* Start from prev offset */
end = -1;
/*
* Start from the beginning does not need to cycle over the
* range, mark it as scanned.
*/
scanned = (index == 0);
} else {
index = wbc->range_start >> PAGE_SHIFT;
end = wbc->range_end >> PAGE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
scanned = 1;
}
/*
* We do the tagged writepage as long as the snapshot flush bit is set
* and we are the first one who do the filemap_flush() on this inode.
*
* The nr_to_write == LONG_MAX is needed to make sure other flushers do
* not race in and drop the bit.
*/
if (range_whole && wbc->nr_to_write == LONG_MAX &&
test_and_clear_bit(BTRFS_INODE_SNAPSHOT_FLUSH,
&BTRFS_I(inode)->runtime_flags))
wbc->tagged_writepages = 1;
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
tag = PAGECACHE_TAG_TOWRITE;
else
tag = PAGECACHE_TAG_DIRTY;
retry:
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
tag_pages_for_writeback(mapping, index, end);
done_index = index;
while (!done && !nr_to_write_done && (index <= end) &&
(nr_folios = filemap_get_folios_tag(mapping, &index,
end, tag, &fbatch))) {
unsigned i;
for (i = 0; i < nr_folios; i++) {
struct folio *folio = fbatch.folios[i];
done_index = folio_next_index(folio);
/*
* At this point we hold neither the i_pages lock nor
* the page lock: the page may be truncated or
* invalidated (changing page->mapping to NULL),
* or even swizzled back from swapper_space to
* tmpfs file mapping
*/
if (!folio_trylock(folio)) {
submit_write_bio(bio_ctrl, 0);
folio_lock(folio);
}
if (unlikely(folio->mapping != mapping)) {
folio_unlock(folio);
continue;
}
if (!folio_test_dirty(folio)) {
/* Someone wrote it for us. */
folio_unlock(folio);
continue;
}
if (wbc->sync_mode != WB_SYNC_NONE) {
if (folio_test_writeback(folio))
submit_write_bio(bio_ctrl, 0);
folio_wait_writeback(folio);
}
if (folio_test_writeback(folio) ||
!folio_clear_dirty_for_io(folio)) {
folio_unlock(folio);
continue;
}
ret = __extent_writepage(&folio->page, bio_ctrl);
if (ret < 0) {
done = 1;
break;
}
/*
* The filesystem may choose to bump up nr_to_write.
* We have to make sure to honor the new nr_to_write
* at any time.
*/
nr_to_write_done = (wbc->sync_mode == WB_SYNC_NONE &&
wbc->nr_to_write <= 0);
}
folio_batch_release(&fbatch);
cond_resched();
}
if (!scanned && !done) {
/*
* We hit the last page and there is more work to be done: wrap
* back to the start of the file
*/
scanned = 1;
index = 0;
/*
* If we're looping we could run into a page that is locked by a
* writer and that writer could be waiting on writeback for a
* page in our current bio, and thus deadlock, so flush the
* write bio here.
*/
submit_write_bio(bio_ctrl, 0);
goto retry;
}
if (wbc->range_cyclic || (wbc->nr_to_write > 0 && range_whole))
mapping->writeback_index = done_index;
btrfs_add_delayed_iput(BTRFS_I(inode));
return ret;
}
/*
* Submit the pages in the range to bio for call sites which delalloc range has
* already been ran (aka, ordered extent inserted) and all pages are still
* locked.
*/
void extent_write_locked_range(struct inode *inode, struct page *locked_page,
u64 start, u64 end, struct writeback_control *wbc,
bool pages_dirty)
{
bool found_error = false;
int ret = 0;
struct address_space *mapping = inode->i_mapping;
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
const u32 sectorsize = fs_info->sectorsize;
loff_t i_size = i_size_read(inode);
u64 cur = start;
struct btrfs_bio_ctrl bio_ctrl = {
.wbc = wbc,
.opf = REQ_OP_WRITE | wbc_to_write_flags(wbc),
};
if (wbc->no_cgroup_owner)
bio_ctrl.opf |= REQ_BTRFS_CGROUP_PUNT;
ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(end + 1, sectorsize));
while (cur <= end) {
u64 cur_end = min(round_down(cur, PAGE_SIZE) + PAGE_SIZE - 1, end);
u32 cur_len = cur_end + 1 - cur;
struct page *page;
int nr = 0;
page = find_get_page(mapping, cur >> PAGE_SHIFT);
ASSERT(PageLocked(page));
if (pages_dirty && page != locked_page) {
ASSERT(PageDirty(page));
clear_page_dirty_for_io(page);
}
ret = __extent_writepage_io(BTRFS_I(inode), page, &bio_ctrl,
i_size, &nr);
if (ret == 1)
goto next_page;
/* Make sure the mapping tag for page dirty gets cleared. */
if (nr == 0) {
set_page_writeback(page);
end_page_writeback(page);
}
if (ret) {
btrfs_mark_ordered_io_finished(BTRFS_I(inode), page,
cur, cur_len, !ret);
mapping_set_error(page->mapping, ret);
}
btrfs_page_unlock_writer(fs_info, page, cur, cur_len);
if (ret < 0)
found_error = true;
next_page:
put_page(page);
cur = cur_end + 1;
}
submit_write_bio(&bio_ctrl, found_error ? ret : 0);
}
int extent_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
int ret = 0;
struct btrfs_bio_ctrl bio_ctrl = {
.wbc = wbc,
.opf = REQ_OP_WRITE | wbc_to_write_flags(wbc),
};
/*
* Allow only a single thread to do the reloc work in zoned mode to
* protect the write pointer updates.
*/
btrfs_zoned_data_reloc_lock(BTRFS_I(inode));
ret = extent_write_cache_pages(mapping, &bio_ctrl);
submit_write_bio(&bio_ctrl, ret);
btrfs_zoned_data_reloc_unlock(BTRFS_I(inode));
return ret;
}
void extent_readahead(struct readahead_control *rac)
{
struct btrfs_bio_ctrl bio_ctrl = { .opf = REQ_OP_READ | REQ_RAHEAD };
struct page *pagepool[16];
struct extent_map *em_cached = NULL;
u64 prev_em_start = (u64)-1;
int nr;
while ((nr = readahead_page_batch(rac, pagepool))) {
u64 contig_start = readahead_pos(rac);
u64 contig_end = contig_start + readahead_batch_length(rac) - 1;
contiguous_readpages(pagepool, nr, contig_start, contig_end,
&em_cached, &bio_ctrl, &prev_em_start);
}
if (em_cached)
free_extent_map(em_cached);
submit_one_bio(&bio_ctrl);
}
/*
* basic invalidate_folio code, this waits on any locked or writeback
* ranges corresponding to the folio, and then deletes any extent state
* records from the tree
*/
int extent_invalidate_folio(struct extent_io_tree *tree,
struct folio *folio, size_t offset)
{
struct extent_state *cached_state = NULL;
u64 start = folio_pos(folio);
u64 end = start + folio_size(folio) - 1;
size_t blocksize = folio->mapping->host->i_sb->s_blocksize;
/* This function is only called for the btree inode */
ASSERT(tree->owner == IO_TREE_BTREE_INODE_IO);
start += ALIGN(offset, blocksize);
if (start > end)
return 0;
lock_extent(tree, start, end, &cached_state);
folio_wait_writeback(folio);
/*
* Currently for btree io tree, only EXTENT_LOCKED is utilized,
* so here we only need to unlock the extent range to free any
* existing extent state.
*/
unlock_extent(tree, start, end, &cached_state);
return 0;
}
/*
* a helper for release_folio, this tests for areas of the page that
* are locked or under IO and drops the related state bits if it is safe
* to drop the page.
*/
static int try_release_extent_state(struct extent_io_tree *tree,
struct page *page, gfp_t mask)
{
u64 start = page_offset(page);
u64 end = start + PAGE_SIZE - 1;
int ret = 1;
if (test_range_bit_exists(tree, start, end, EXTENT_LOCKED)) {
ret = 0;
} else {
u32 clear_bits = ~(EXTENT_LOCKED | EXTENT_NODATASUM |
EXTENT_DELALLOC_NEW | EXTENT_CTLBITS |
EXTENT_QGROUP_RESERVED);
/*
* At this point we can safely clear everything except the
* locked bit, the nodatasum bit and the delalloc new bit.
* The delalloc new bit will be cleared by ordered extent
* completion.
*/
ret = __clear_extent_bit(tree, start, end, clear_bits, NULL, NULL);
/* if clear_extent_bit failed for enomem reasons,
* we can't allow the release to continue.
*/
if (ret < 0)
ret = 0;
else
ret = 1;
}
return ret;
}
/*
* a helper for release_folio. As long as there are no locked extents
* in the range corresponding to the page, both state records and extent
* map records are removed
*/
int try_release_extent_mapping(struct page *page, gfp_t mask)
{
struct extent_map *em;
u64 start = page_offset(page);
u64 end = start + PAGE_SIZE - 1;
struct btrfs_inode *btrfs_inode = BTRFS_I(page->mapping->host);
struct extent_io_tree *tree = &btrfs_inode->io_tree;
struct extent_map_tree *map = &btrfs_inode->extent_tree;
if (gfpflags_allow_blocking(mask) &&
page->mapping->host->i_size > SZ_16M) {
u64 len;
while (start <= end) {
struct btrfs_fs_info *fs_info;
u64 cur_gen;
len = end - start + 1;
write_lock(&map->lock);
em = lookup_extent_mapping(map, start, len);
if (!em) {
write_unlock(&map->lock);
break;
}
if ((em->flags & EXTENT_FLAG_PINNED) ||
em->start != start) {
write_unlock(&map->lock);
free_extent_map(em);
break;
}
if (test_range_bit_exists(tree, em->start,
extent_map_end(em) - 1,
EXTENT_LOCKED))
goto next;
/*
* If it's not in the list of modified extents, used
* by a fast fsync, we can remove it. If it's being
* logged we can safely remove it since fsync took an
* extra reference on the em.
*/
if (list_empty(&em->list) ||
(em->flags & EXTENT_FLAG_LOGGING))
goto remove_em;
/*
* If it's in the list of modified extents, remove it
* only if its generation is older then the current one,
* in which case we don't need it for a fast fsync.
* Otherwise don't remove it, we could be racing with an
* ongoing fast fsync that could miss the new extent.
*/
fs_info = btrfs_inode->root->fs_info;
spin_lock(&fs_info->trans_lock);
cur_gen = fs_info->generation;
spin_unlock(&fs_info->trans_lock);
if (em->generation >= cur_gen)
goto next;
remove_em:
/*
* We only remove extent maps that are not in the list of
* modified extents or that are in the list but with a
* generation lower then the current generation, so there
* is no need to set the full fsync flag on the inode (it
* hurts the fsync performance for workloads with a data
* size that exceeds or is close to the system's memory).
*/
remove_extent_mapping(map, em);
/* once for the rb tree */
free_extent_map(em);
next:
start = extent_map_end(em);
write_unlock(&map->lock);
/* once for us */
free_extent_map(em);
cond_resched(); /* Allow large-extent preemption. */
}
}
return try_release_extent_state(tree, page, mask);
}
/*
* To cache previous fiemap extent
*
* Will be used for merging fiemap extent
*/
struct fiemap_cache {
u64 offset;
u64 phys;
u64 len;
u32 flags;
bool cached;
};
/*
* Helper to submit fiemap extent.
*
* Will try to merge current fiemap extent specified by @offset, @phys,
* @len and @flags with cached one.
* And only when we fails to merge, cached one will be submitted as
* fiemap extent.
*
* Return value is the same as fiemap_fill_next_extent().
*/
static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
u64 offset, u64 phys, u64 len, u32 flags)
{
int ret = 0;
/* Set at the end of extent_fiemap(). */
ASSERT((flags & FIEMAP_EXTENT_LAST) == 0);
if (!cache->cached)
goto assign;
/*
* Sanity check, extent_fiemap() should have ensured that new
* fiemap extent won't overlap with cached one.
* Not recoverable.
*
* NOTE: Physical address can overlap, due to compression
*/
if (cache->offset + cache->len > offset) {
WARN_ON(1);
return -EINVAL;
}
/*
* Only merges fiemap extents if
* 1) Their logical addresses are continuous
*
* 2) Their physical addresses are continuous
* So truly compressed (physical size smaller than logical size)
* extents won't get merged with each other
*
* 3) Share same flags
*/
if (cache->offset + cache->len == offset &&
cache->phys + cache->len == phys &&
cache->flags == flags) {
cache->len += len;
return 0;
}
/* Not mergeable, need to submit cached one */
ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
cache->len, cache->flags);
cache->cached = false;
if (ret)
return ret;
assign:
cache->cached = true;
cache->offset = offset;
cache->phys = phys;
cache->len = len;
cache->flags = flags;
return 0;
}
/*
* Emit last fiemap cache
*
* The last fiemap cache may still be cached in the following case:
* 0 4k 8k
* |<- Fiemap range ->|
* |<------------ First extent ----------->|
*
* In this case, the first extent range will be cached but not emitted.
* So we must emit it before ending extent_fiemap().
*/
static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache)
{
int ret;
if (!cache->cached)
return 0;
ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
cache->len, cache->flags);
cache->cached = false;
if (ret > 0)
ret = 0;
return ret;
}
static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path)
{
struct extent_buffer *clone;
struct btrfs_key key;
int slot;
int ret;
path->slots[0]++;
if (path->slots[0] < btrfs_header_nritems(path->nodes[0]))
return 0;
ret = btrfs_next_leaf(inode->root, path);
if (ret != 0)
return ret;
/*
* Don't bother with cloning if there are no more file extent items for
* our inode.
*/
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY)
return 1;
/* See the comment at fiemap_search_slot() about why we clone. */
clone = btrfs_clone_extent_buffer(path->nodes[0]);
if (!clone)
return -ENOMEM;
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
return 0;
}
/*
* Search for the first file extent item that starts at a given file offset or
* the one that starts immediately before that offset.
* Returns: 0 on success, < 0 on error, 1 if not found.
*/
static int fiemap_search_slot(struct btrfs_inode *inode, struct btrfs_path *path,
u64 file_offset)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *clone;
struct btrfs_key key;
int slot;
int ret;
key.objectid = ino;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = file_offset;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
return ret;
if (ret > 0 && path->slots[0] > 0) {
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0] - 1);
if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY)
path->slots[0]--;
}
if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
ret = btrfs_next_leaf(root, path);
if (ret != 0)
return ret;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
return 1;
}
/*
* We clone the leaf and use it during fiemap. This is because while
* using the leaf we do expensive things like checking if an extent is
* shared, which can take a long time. In order to prevent blocking
* other tasks for too long, we use a clone of the leaf. We have locked
* the file range in the inode's io tree, so we know none of our file
* extent items can change. This way we avoid blocking other tasks that
* want to insert items for other inodes in the same leaf or b+tree
* rebalance operations (triggered for example when someone is trying
* to push items into this leaf when trying to insert an item in a
* neighbour leaf).
* We also need the private clone because holding a read lock on an
* extent buffer of the subvolume's b+tree will make lockdep unhappy
* when we call fiemap_fill_next_extent(), because that may cause a page
* fault when filling the user space buffer with fiemap data.
*/
clone = btrfs_clone_extent_buffer(path->nodes[0]);
if (!clone)
return -ENOMEM;
slot = path->slots[0];
btrfs_release_path(path);
path->nodes[0] = clone;
path->slots[0] = slot;
return 0;
}
/*
* Process a range which is a hole or a prealloc extent in the inode's subvolume
* btree. If @disk_bytenr is 0, we are dealing with a hole, otherwise a prealloc
* extent. The end offset (@end) is inclusive.
*/
static int fiemap_process_hole(struct btrfs_inode *inode,
struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
struct extent_state **delalloc_cached_state,
struct btrfs_backref_share_check_ctx *backref_ctx,
u64 disk_bytenr, u64 extent_offset,
u64 extent_gen,
u64 start, u64 end)
{
const u64 i_size = i_size_read(&inode->vfs_inode);
u64 cur_offset = start;
u64 last_delalloc_end = 0;
u32 prealloc_flags = FIEMAP_EXTENT_UNWRITTEN;
bool checked_extent_shared = false;
int ret;
/*
* There can be no delalloc past i_size, so don't waste time looking for
* it beyond i_size.
*/
while (cur_offset < end && cur_offset < i_size) {
u64 delalloc_start;
u64 delalloc_end;
u64 prealloc_start;
u64 prealloc_len = 0;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode, cur_offset, end,
delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
break;
/*
* If this is a prealloc extent we have to report every section
* of it that has no delalloc.
*/
if (disk_bytenr != 0) {
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = delalloc_start - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = delalloc_start - prealloc_start;
}
}
if (prealloc_len > 0) {
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
checked_extent_shared = true;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
extent_offset += prealloc_len;
}
ret = emit_fiemap_extent(fieinfo, cache, delalloc_start, 0,
delalloc_end + 1 - delalloc_start,
FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
if (ret)
return ret;
last_delalloc_end = delalloc_end;
cur_offset = delalloc_end + 1;
extent_offset += cur_offset - delalloc_start;
cond_resched();
}
/*
* Either we found no delalloc for the whole prealloc extent or we have
* a prealloc extent that spans i_size or starts at or after i_size.
*/
if (disk_bytenr != 0 && last_delalloc_end < end) {
u64 prealloc_start;
u64 prealloc_len;
if (last_delalloc_end == 0) {
prealloc_start = start;
prealloc_len = end + 1 - start;
} else {
prealloc_start = last_delalloc_end + 1;
prealloc_len = end + 1 - prealloc_start;
}
if (!checked_extent_shared && fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
return ret;
else if (ret > 0)
prealloc_flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, cache, prealloc_start,
disk_bytenr + extent_offset,
prealloc_len, prealloc_flags);
if (ret)
return ret;
}
return 0;
}
static int fiemap_find_last_extent_offset(struct btrfs_inode *inode,
struct btrfs_path *path,
u64 *last_extent_end_ret)
{
const u64 ino = btrfs_ino(inode);
struct btrfs_root *root = inode->root;
struct extent_buffer *leaf;
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 disk_bytenr;
int ret;
/*
* Lookup the last file extent. We're not using i_size here because
* there might be preallocation past i_size.
*/
ret = btrfs_lookup_file_extent(NULL, root, path, ino, (u64)-1, 0);
/* There can't be a file extent item at offset (u64)-1 */
ASSERT(ret != 0);
if (ret < 0)
return ret;
/*
* For a non-existing key, btrfs_search_slot() always leaves us at a
* slot > 0, except if the btree is empty, which is impossible because
* at least it has the inode item for this inode and all the items for
* the root inode 256.
*/
ASSERT(path->slots[0] > 0);
path->slots[0]--;
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) {
/* No file extent items in the subvolume tree. */
*last_extent_end_ret = 0;
return 0;
}
/*
* For an inline extent, the disk_bytenr is where inline data starts at,
* so first check if we have an inline extent item before checking if we
* have an implicit hole (disk_bytenr == 0).
*/
ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item);
if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_INLINE) {
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
/*
* Find the last file extent item that is not a hole (when NO_HOLES is
* not enabled). This should take at most 2 iterations in the worst
* case: we have one hole file extent item at slot 0 of a leaf and
* another hole file extent item as the last item in the previous leaf.
* This is because we merge file extent items that represent holes.
*/
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
while (disk_bytenr == 0) {
ret = btrfs_previous_item(root, path, ino, BTRFS_EXTENT_DATA_KEY);
if (ret < 0) {
return ret;
} else if (ret > 0) {
/* No file extent items that are not holes. */
*last_extent_end_ret = 0;
return 0;
}
leaf = path->nodes[0];
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
}
*last_extent_end_ret = btrfs_file_extent_end(path);
return 0;
}
int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
const u64 ino = btrfs_ino(inode);
struct extent_state *cached_state = NULL;
struct extent_state *delalloc_cached_state = NULL;
struct btrfs_path *path;
struct fiemap_cache cache = { 0 };
struct btrfs_backref_share_check_ctx *backref_ctx;
u64 last_extent_end;
u64 prev_extent_end;
u64 lockstart;
u64 lockend;
bool stopped = false;
int ret;
backref_ctx = btrfs_alloc_backref_share_check_ctx();
path = btrfs_alloc_path();
if (!backref_ctx || !path) {
ret = -ENOMEM;
goto out;
}
lockstart = round_down(start, inode->root->fs_info->sectorsize);
lockend = round_up(start + len, inode->root->fs_info->sectorsize);
prev_extent_end = lockstart;
btrfs_inode_lock(inode, BTRFS_ILOCK_SHARED);
lock_extent(&inode->io_tree, lockstart, lockend, &cached_state);
ret = fiemap_find_last_extent_offset(inode, path, &last_extent_end);
if (ret < 0)
goto out_unlock;
btrfs_release_path(path);
path->reada = READA_FORWARD;
ret = fiemap_search_slot(inode, path, lockstart);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/*
* No file extent item found, but we may have delalloc between
* the current offset and i_size. So check for that.
*/
ret = 0;
goto check_eof_delalloc;
}
while (prev_extent_end < lockend) {
struct extent_buffer *leaf = path->nodes[0];
struct btrfs_file_extent_item *ei;
struct btrfs_key key;
u64 extent_end;
u64 extent_len;
u64 extent_offset = 0;
u64 extent_gen;
u64 disk_bytenr = 0;
u64 flags = 0;
int extent_type;
u8 compression;
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
break;
extent_end = btrfs_file_extent_end(path);
/*
* The first iteration can leave us at an extent item that ends
* before our range's start. Move to the next item.
*/
if (extent_end <= lockstart)
goto next_item;
backref_ctx->curr_leaf_bytenr = leaf->start;
/* We have in implicit hole (NO_HOLES feature enabled). */
if (prev_extent_end < key.offset) {
const u64 range_end = min(key.offset, lockend) - 1;
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
prev_extent_end, range_end);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* fiemap_fill_next_extent() told us to stop. */
stopped = true;
break;
}
/* We've reached the end of the fiemap range, stop. */
if (key.offset >= lockend) {
stopped = true;
break;
}
}
extent_len = extent_end - key.offset;
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_file_extent_item);
compression = btrfs_file_extent_compression(leaf, ei);
extent_type = btrfs_file_extent_type(leaf, ei);
extent_gen = btrfs_file_extent_generation(leaf, ei);
if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei);
if (compression == BTRFS_COMPRESS_NONE)
extent_offset = btrfs_file_extent_offset(leaf, ei);
}
if (compression != BTRFS_COMPRESS_NONE)
flags |= FIEMAP_EXTENT_ENCODED;
if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
flags |= FIEMAP_EXTENT_DATA_INLINE;
flags |= FIEMAP_EXTENT_NOT_ALIGNED;
ret = emit_fiemap_extent(fieinfo, &cache, key.offset, 0,
extent_len, flags);
} else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx,
disk_bytenr, extent_offset,
extent_gen, key.offset,
extent_end - 1);
} else if (disk_bytenr == 0) {
/* We have an explicit hole. */
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
key.offset, extent_end - 1);
} else {
/* We have a regular extent. */
if (fieinfo->fi_extents_max) {
ret = btrfs_is_data_extent_shared(inode,
disk_bytenr,
extent_gen,
backref_ctx);
if (ret < 0)
goto out_unlock;
else if (ret > 0)
flags |= FIEMAP_EXTENT_SHARED;
}
ret = emit_fiemap_extent(fieinfo, &cache, key.offset,
disk_bytenr + extent_offset,
extent_len, flags);
}
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* fiemap_fill_next_extent() told us to stop. */
stopped = true;
break;
}
prev_extent_end = extent_end;
next_item:
if (fatal_signal_pending(current)) {
ret = -EINTR;
goto out_unlock;
}
ret = fiemap_next_leaf_item(inode, path);
if (ret < 0) {
goto out_unlock;
} else if (ret > 0) {
/* No more file extent items for this inode. */
break;
}
cond_resched();
}
check_eof_delalloc:
/*
* Release (and free) the path before emitting any final entries to
* fiemap_fill_next_extent() to keep lockdep happy. This is because
* once we find no more file extent items exist, we may have a
* non-cloned leaf, and fiemap_fill_next_extent() can trigger page
* faults when copying data to the user space buffer.
*/
btrfs_free_path(path);
path = NULL;
if (!stopped && prev_extent_end < lockend) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state, backref_ctx,
0, 0, 0, prev_extent_end, lockend - 1);
if (ret < 0)
goto out_unlock;
prev_extent_end = lockend;
}
if (cache.cached && cache.offset + cache.len >= last_extent_end) {
const u64 i_size = i_size_read(&inode->vfs_inode);
if (prev_extent_end < i_size) {
u64 delalloc_start;
u64 delalloc_end;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode,
prev_extent_end,
i_size - 1,
&delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
cache.flags |= FIEMAP_EXTENT_LAST;
} else {
cache.flags |= FIEMAP_EXTENT_LAST;
}
}
ret = emit_last_fiemap_cache(fieinfo, &cache);
out_unlock:
unlock_extent(&inode->io_tree, lockstart, lockend, &cached_state);
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
out:
free_extent_state(delalloc_cached_state);
btrfs_free_backref_share_ctx(backref_ctx);
btrfs_free_path(path);
return ret;
}
static void __free_extent_buffer(struct extent_buffer *eb)
{
kmem_cache_free(extent_buffer_cache, eb);
}
static int extent_buffer_under_io(const struct extent_buffer *eb)
{
return (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
}
static bool page_range_has_eb(struct btrfs_fs_info *fs_info, struct page *page)
{
struct folio *folio = page_folio(page);
struct btrfs_subpage *subpage;
lockdep_assert_held(&page->mapping->private_lock);
if (folio_test_private(folio)) {
subpage = folio_get_private(folio);
if (atomic_read(&subpage->eb_refs))
return true;
/*
* Even there is no eb refs here, we may still have
* end_page_read() call relying on page::private.
*/
if (atomic_read(&subpage->readers))
return true;
}
return false;
}
static void detach_extent_buffer_page(struct extent_buffer *eb, struct page *page)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
const bool mapped = !test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags);
struct folio *folio = page_folio(page);
/*
* For mapped eb, we're going to change the folio private, which should
* be done under the private_lock.
*/
if (mapped)
spin_lock(&page->mapping->private_lock);
if (!folio_test_private(folio)) {
if (mapped)
spin_unlock(&page->mapping->private_lock);
return;
}
if (fs_info->nodesize >= PAGE_SIZE) {
/*
* We do this since we'll remove the pages after we've
* removed the eb from the radix tree, so we could race
* and have this page now attached to the new eb. So
* only clear folio if it's still connected to
* this eb.
*/
if (folio_test_private(folio) && folio_get_private(folio) == eb) {
BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
BUG_ON(PageDirty(page));
BUG_ON(PageWriteback(page));
/* We need to make sure we haven't be attached to a new eb. */
folio_detach_private(folio);
}
if (mapped)
spin_unlock(&page->mapping->private_lock);
return;
}
/*
* For subpage, we can have dummy eb with folio private attached. In
* this case, we can directly detach the private as such folio is only
* attached to one dummy eb, no sharing.
*/
if (!mapped) {
btrfs_detach_subpage(fs_info, page);
return;
}
btrfs_page_dec_eb_refs(fs_info, page);
/*
* We can only detach the folio private if there are no other ebs in the
* page range and no unfinished IO.
*/
if (!page_range_has_eb(fs_info, page))
btrfs_detach_subpage(fs_info, page);
spin_unlock(&page->mapping->private_lock);
}
/* Release all pages attached to the extent buffer */
static void btrfs_release_extent_buffer_pages(struct extent_buffer *eb)
{
int i;
int num_pages;
ASSERT(!extent_buffer_under_io(eb));
num_pages = num_extent_pages(eb);
for (i = 0; i < num_pages; i++) {
struct page *page = eb->pages[i];
if (!page)
continue;
detach_extent_buffer_page(eb, page);
/* One for when we allocated the page */
put_page(page);
}
}
/*
* Helper for releasing the extent buffer.
*/
static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
{
btrfs_release_extent_buffer_pages(eb);
btrfs_leak_debug_del_eb(eb);
__free_extent_buffer(eb);
}
static struct extent_buffer *
__alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
unsigned long len)
{
struct extent_buffer *eb = NULL;
eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
eb->start = start;
eb->len = len;
eb->fs_info = fs_info;
init_rwsem(&eb->lock);
btrfs_leak_debug_add_eb(eb);
spin_lock_init(&eb->refs_lock);
atomic_set(&eb->refs, 1);
ASSERT(len <= BTRFS_MAX_METADATA_BLOCKSIZE);
return eb;
}
struct extent_buffer *btrfs_clone_extent_buffer(const struct extent_buffer *src)
{
int i;
struct extent_buffer *new;
int num_pages = num_extent_pages(src);
int ret;
new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
if (new == NULL)
return NULL;
/*
* Set UNMAPPED before calling btrfs_release_extent_buffer(), as
* btrfs_release_extent_buffer() have different behavior for
* UNMAPPED subpage extent buffer.
*/
set_bit(EXTENT_BUFFER_UNMAPPED, &new->bflags);
ret = btrfs_alloc_page_array(num_pages, new->pages, 0);
if (ret) {
btrfs_release_extent_buffer(new);
return NULL;
}
for (i = 0; i < num_pages; i++) {
int ret;
struct page *p = new->pages[i];
ret = attach_extent_buffer_page(new, p, NULL);
if (ret < 0) {
btrfs_release_extent_buffer(new);
return NULL;
}
WARN_ON(PageDirty(p));
}
copy_extent_buffer_full(new, src);
set_extent_buffer_uptodate(new);
return new;
}
struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
u64 start, unsigned long len)
{
struct extent_buffer *eb;
int num_pages;
int i;
int ret;
eb = __alloc_extent_buffer(fs_info, start, len);
if (!eb)
return NULL;
num_pages = num_extent_pages(eb);
ret = btrfs_alloc_page_array(num_pages, eb->pages, 0);
if (ret)
goto err;
for (i = 0; i < num_pages; i++) {
struct page *p = eb->pages[i];
ret = attach_extent_buffer_page(eb, p, NULL);
if (ret < 0)
goto err;
}
set_extent_buffer_uptodate(eb);
btrfs_set_header_nritems(eb, 0);
set_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags);
return eb;
err:
for (i = 0; i < num_pages; i++) {
if (eb->pages[i]) {
detach_extent_buffer_page(eb, eb->pages[i]);
__free_page(eb->pages[i]);
}
}
__free_extent_buffer(eb);
return NULL;
}
struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
u64 start)
{
return __alloc_dummy_extent_buffer(fs_info, start, fs_info->nodesize);
}
static void check_buffer_tree_ref(struct extent_buffer *eb)
{
int refs;
/*
* The TREE_REF bit is first set when the extent_buffer is added
* to the radix tree. It is also reset, if unset, when a new reference
* is created by find_extent_buffer.
*
* It is only cleared in two cases: freeing the last non-tree
* reference to the extent_buffer when its STALE bit is set or
* calling release_folio when the tree reference is the only reference.
*
* In both cases, care is taken to ensure that the extent_buffer's
* pages are not under io. However, release_folio can be concurrently
* called with creating new references, which is prone to race
* conditions between the calls to check_buffer_tree_ref in those
* codepaths and clearing TREE_REF in try_release_extent_buffer.
*
* The actual lifetime of the extent_buffer in the radix tree is
* adequately protected by the refcount, but the TREE_REF bit and
* its corresponding reference are not. To protect against this
* class of races, we call check_buffer_tree_ref from the codepaths
* which trigger io. Note that once io is initiated, TREE_REF can no
* longer be cleared, so that is the moment at which any such race is
* best fixed.
*/
refs = atomic_read(&eb->refs);
if (refs >= 2 && test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
return;
spin_lock(&eb->refs_lock);
if (!test_and_set_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
atomic_inc(&eb->refs);
spin_unlock(&eb->refs_lock);
}
static void mark_extent_buffer_accessed(struct extent_buffer *eb,
struct page *accessed)
{
int num_pages, i;
check_buffer_tree_ref(eb);
num_pages = num_extent_pages(eb);
for (i = 0; i < num_pages; i++) {
struct page *p = eb->pages[i];
if (p != accessed)
mark_page_accessed(p);
}
}
struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
u64 start)
{
struct extent_buffer *eb;
eb = find_extent_buffer_nolock(fs_info, start);
if (!eb)
return NULL;
/*
* Lock our eb's refs_lock to avoid races with free_extent_buffer().
* When we get our eb it might be flagged with EXTENT_BUFFER_STALE and
* another task running free_extent_buffer() might have seen that flag
* set, eb->refs == 2, that the buffer isn't under IO (dirty and
* writeback flags not set) and it's still in the tree (flag
* EXTENT_BUFFER_TREE_REF set), therefore being in the process of
* decrementing the extent buffer's reference count twice. So here we
* could race and increment the eb's reference count, clear its stale
* flag, mark it as dirty and drop our reference before the other task
* finishes executing free_extent_buffer, which would later result in
* an attempt to free an extent buffer that is dirty.
*/
if (test_bit(EXTENT_BUFFER_STALE, &eb->bflags)) {
spin_lock(&eb->refs_lock);
spin_unlock(&eb->refs_lock);
}
mark_extent_buffer_accessed(eb, NULL);
return eb;
}
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
u64 start)
{
struct extent_buffer *eb, *exists = NULL;
int ret;
eb = find_extent_buffer(fs_info, start);
if (eb)
return eb;
eb = alloc_dummy_extent_buffer(fs_info, start);
if (!eb)
return ERR_PTR(-ENOMEM);
eb->fs_info = fs_info;
again:
ret = radix_tree_preload(GFP_NOFS);
if (ret) {
exists = ERR_PTR(ret);
goto free_eb;
}
spin_lock(&fs_info->buffer_lock);
ret = radix_tree_insert(&fs_info->buffer_radix,
start >> fs_info->sectorsize_bits, eb);
spin_unlock(&fs_info->buffer_lock);
radix_tree_preload_end();
if (ret == -EEXIST) {
exists = find_extent_buffer(fs_info, start);
if (exists)
goto free_eb;
else
goto again;
}
check_buffer_tree_ref(eb);
set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
return eb;
free_eb:
btrfs_release_extent_buffer(eb);
return exists;
}
#endif
static struct extent_buffer *grab_extent_buffer(
struct btrfs_fs_info *fs_info, struct page *page)
{
struct folio *folio = page_folio(page);
struct extent_buffer *exists;
/*
* For subpage case, we completely rely on radix tree to ensure we
* don't try to insert two ebs for the same bytenr. So here we always
* return NULL and just continue.
*/
if (fs_info->nodesize < PAGE_SIZE)
return NULL;
/* Page not yet attached to an extent buffer */
if (!folio_test_private(folio))
return NULL;
/*
* We could have already allocated an eb for this page and attached one
* so lets see if we can get a ref on the existing eb, and if we can we
* know it's good and we can just return that one, else we know we can
* just overwrite folio private.
*/
exists = folio_get_private(folio);
if (atomic_inc_not_zero(&exists->refs))
return exists;
WARN_ON(PageDirty(page));
folio_detach_private(folio);
return NULL;
}
static int check_eb_alignment(struct btrfs_fs_info *fs_info, u64 start)
{
if (!IS_ALIGNED(start, fs_info->sectorsize)) {
btrfs_err(fs_info, "bad tree block start %llu", start);
return -EINVAL;
}
if (fs_info->nodesize < PAGE_SIZE &&
offset_in_page(start) + fs_info->nodesize > PAGE_SIZE) {
btrfs_err(fs_info,
"tree block crosses page boundary, start %llu nodesize %u",
start, fs_info->nodesize);
return -EINVAL;
}
if (fs_info->nodesize >= PAGE_SIZE &&
!PAGE_ALIGNED(start)) {
btrfs_err(fs_info,
"tree block is not page aligned, start %llu nodesize %u",
start, fs_info->nodesize);
return -EINVAL;
}
if (!IS_ALIGNED(start, fs_info->nodesize) &&
!test_and_set_bit(BTRFS_FS_UNALIGNED_TREE_BLOCK, &fs_info->flags)) {
btrfs_warn(fs_info,
"tree block not nodesize aligned, start %llu nodesize %u, can be resolved by a full metadata balance",
start, fs_info->nodesize);
}
return 0;
}
/*
* Return 0 if eb->pages[i] is attached to btree inode successfully.
* Return >0 if there is already annother extent buffer for the range,
* and @found_eb_ret would be updated.
*/
static int attach_eb_page_to_filemap(struct extent_buffer *eb, int i,
struct extent_buffer **found_eb_ret)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
struct address_space *mapping = fs_info->btree_inode->i_mapping;
const unsigned long index = eb->start >> PAGE_SHIFT;
struct folio *existing_folio;
int ret;
ASSERT(found_eb_ret);
/* Caller should ensure the page exists. */
ASSERT(eb->pages[i]);
retry:
ret = filemap_add_folio(mapping, page_folio(eb->pages[i]), index + i,
GFP_NOFS | __GFP_NOFAIL);
if (!ret)
return 0;
existing_folio = filemap_lock_folio(mapping, index + i);
/* The page cache only exists for a very short time, just retry. */
if (IS_ERR(existing_folio))
goto retry;
/* For now, we should only have single-page folios for btree inode. */
ASSERT(folio_nr_pages(existing_folio) == 1);
if (fs_info->nodesize < PAGE_SIZE) {
/*
* We're going to reuse the existing page, can drop our page
* and subpage structure now.
*/
__free_page(eb->pages[i]);
eb->pages[i] = folio_page(existing_folio, 0);
} else {
struct extent_buffer *existing_eb;
existing_eb = grab_extent_buffer(fs_info,
folio_page(existing_folio, 0));
if (existing_eb) {
/* The extent buffer still exists, we can use it directly. */
*found_eb_ret = existing_eb;
folio_unlock(existing_folio);
folio_put(existing_folio);
return 1;
}
/* The extent buffer no longer exists, we can reuse the folio. */
__free_page(eb->pages[i]);
eb->pages[i] = folio_page(existing_folio, 0);
}
return 0;
}
struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
u64 start, u64 owner_root, int level)
{
unsigned long len = fs_info->nodesize;
int num_pages;
int attached = 0;
struct extent_buffer *eb;
struct extent_buffer *existing_eb = NULL;
struct address_space *mapping = fs_info->btree_inode->i_mapping;
struct btrfs_subpage *prealloc = NULL;
u64 lockdep_owner = owner_root;
bool page_contig = true;
int uptodate = 1;
int ret;
if (check_eb_alignment(fs_info, start))
return ERR_PTR(-EINVAL);
#if BITS_PER_LONG == 32
if (start >= MAX_LFS_FILESIZE) {
btrfs_err_rl(fs_info,
"extent buffer %llu is beyond 32bit page cache limit", start);
btrfs_err_32bit_limit(fs_info);
return ERR_PTR(-EOVERFLOW);
}
if (start >= BTRFS_32BIT_EARLY_WARN_THRESHOLD)
btrfs_warn_32bit_limit(fs_info);
#endif
eb = find_extent_buffer(fs_info, start);
if (eb)
return eb;
eb = __alloc_extent_buffer(fs_info, start, len);
if (!eb)
return ERR_PTR(-ENOMEM);
/*
* The reloc trees are just snapshots, so we need them to appear to be
* just like any other fs tree WRT lockdep.
*/
if (lockdep_owner == BTRFS_TREE_RELOC_OBJECTID)
lockdep_owner = BTRFS_FS_TREE_OBJECTID;
btrfs_set_buffer_lockdep_class(lockdep_owner, eb, level);
num_pages = num_extent_pages(eb);
/*
* Preallocate folio private for subpage case, so that we won't
* allocate memory with private_lock nor page lock hold.
*
* The memory will be freed by attach_extent_buffer_page() or freed
* manually if we exit earlier.
*/
if (fs_info->nodesize < PAGE_SIZE) {
prealloc = btrfs_alloc_subpage(fs_info, BTRFS_SUBPAGE_METADATA);
if (IS_ERR(prealloc)) {
ret = PTR_ERR(prealloc);
goto out;
}
}
/* Allocate all pages first. */
ret = btrfs_alloc_page_array(num_pages, eb->pages, __GFP_NOFAIL);
if (ret < 0) {
btrfs_free_subpage(prealloc);
goto out;
}
/* Attach all pages to the filemap. */
for (int i = 0; i < num_pages; i++) {
struct page *p;
ret = attach_eb_page_to_filemap(eb, i, &existing_eb);
if (ret > 0) {
ASSERT(existing_eb);
goto out;
}
attached++;
/*
* Only after attach_eb_page_to_filemap(), eb->pages[] is
* reliable, as we may choose to reuse the existing page cache
* and free the allocated page.
*/
p = eb->pages[i];
spin_lock(&mapping->private_lock);
/* Should not fail, as we have preallocated the memory */
ret = attach_extent_buffer_page(eb, p, prealloc);
ASSERT(!ret);
/*
* To inform we have extra eb under allocation, so that
* detach_extent_buffer_page() won't release the folio private
* when the eb hasn't yet been inserted into radix tree.
*
* The ref will be decreased when the eb released the page, in
* detach_extent_buffer_page().
* Thus needs no special handling in error path.
*/
btrfs_page_inc_eb_refs(fs_info, p);
spin_unlock(&mapping->private_lock);
WARN_ON(btrfs_page_test_dirty(fs_info, p, eb->start, eb->len));
/*
* Check if the current page is physically contiguous with previous eb
* page.
*/
if (i && eb->pages[i - 1] + 1 != p)
page_contig = false;
if (!btrfs_page_test_uptodate(fs_info, p, eb->start, eb->len))
uptodate = 0;
/*
* We can't unlock the pages just yet since the extent buffer
* hasn't been properly inserted in the radix tree, this
* opens a race with btree_release_folio which can free a page
* while we are still filling in all pages for the buffer and
* we could crash.
*/
}
if (uptodate)
set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
/* All pages are physically contiguous, can skip cross page handling. */
if (page_contig)
eb->addr = page_address(eb->pages[0]) + offset_in_page(eb->start);
again:
ret = radix_tree_preload(GFP_NOFS);
if (ret)
goto out;
spin_lock(&fs_info->buffer_lock);
ret = radix_tree_insert(&fs_info->buffer_radix,
start >> fs_info->sectorsize_bits, eb);
spin_unlock(&fs_info->buffer_lock);
radix_tree_preload_end();
if (ret == -EEXIST) {
ret = 0;
existing_eb = find_extent_buffer(fs_info, start);
if (existing_eb)
goto out;
else
goto again;
}
/* add one reference for the tree */
check_buffer_tree_ref(eb);
set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
/*
* Now it's safe to unlock the pages because any calls to
* btree_release_folio will correctly detect that a page belongs to a
* live buffer and won't free them prematurely.
*/
for (int i = 0; i < num_pages; i++)
unlock_page(eb->pages[i]);
return eb;
out:
WARN_ON(!atomic_dec_and_test(&eb->refs));
for (int i = 0; i < attached; i++) {
ASSERT(eb->pages[i]);
detach_extent_buffer_page(eb, eb->pages[i]);
unlock_page(eb->pages[i]);
}
/*
* Now all pages of that extent buffer is unmapped, set UNMAPPED flag,
* so it can be cleaned up without utlizing page->mapping.
*/
set_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags);
btrfs_release_extent_buffer(eb);
if (ret < 0)
return ERR_PTR(ret);
ASSERT(existing_eb);
return existing_eb;
}
static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
{
struct extent_buffer *eb =
container_of(head, struct extent_buffer, rcu_head);
__free_extent_buffer(eb);
}
static int release_extent_buffer(struct extent_buffer *eb)
__releases(&eb->refs_lock)
{
lockdep_assert_held(&eb->refs_lock);
WARN_ON(atomic_read(&eb->refs) == 0);
if (atomic_dec_and_test(&eb->refs)) {
if (test_and_clear_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags)) {
struct btrfs_fs_info *fs_info = eb->fs_info;
spin_unlock(&eb->refs_lock);
spin_lock(&fs_info->buffer_lock);
radix_tree_delete(&fs_info->buffer_radix,
eb->start >> fs_info->sectorsize_bits);
spin_unlock(&fs_info->buffer_lock);
} else {
spin_unlock(&eb->refs_lock);
}
btrfs_leak_debug_del_eb(eb);
/* Should be safe to release our pages at this point */
btrfs_release_extent_buffer_pages(eb);
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
if (unlikely(test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags))) {
__free_extent_buffer(eb);
return 1;
}
#endif
call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
return 1;
}
spin_unlock(&eb->refs_lock);
return 0;
}
void free_extent_buffer(struct extent_buffer *eb)
{
int refs;
if (!eb)
return;
refs = atomic_read(&eb->refs);
while (1) {
if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3)
|| (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) &&
refs == 1))
break;
if (atomic_try_cmpxchg(&eb->refs, &refs, refs - 1))
return;
}
spin_lock(&eb->refs_lock);
if (atomic_read(&eb->refs) == 2 &&
test_bit(EXTENT_BUFFER_STALE, &eb->bflags) &&
!extent_buffer_under_io(eb) &&
test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
atomic_dec(&eb->refs);
/*
* I know this is terrible, but it's temporary until we stop tracking
* the uptodate bits and such for the extent buffers.
*/
release_extent_buffer(eb);
}
void free_extent_buffer_stale(struct extent_buffer *eb)
{
if (!eb)
return;
spin_lock(&eb->refs_lock);
set_bit(EXTENT_BUFFER_STALE, &eb->bflags);
if (atomic_read(&eb->refs) == 2 && !extent_buffer_under_io(eb) &&
test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
atomic_dec(&eb->refs);
release_extent_buffer(eb);
}
static void btree_clear_page_dirty(struct page *page)
{
ASSERT(PageDirty(page));
ASSERT(PageLocked(page));
clear_page_dirty_for_io(page);
xa_lock_irq(&page->mapping->i_pages);
if (!PageDirty(page))
__xa_clear_mark(&page->mapping->i_pages,
page_index(page), PAGECACHE_TAG_DIRTY);
xa_unlock_irq(&page->mapping->i_pages);
}
static void clear_subpage_extent_buffer_dirty(const struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
struct page *page = eb->pages[0];
bool last;
/* btree_clear_page_dirty() needs page locked */
lock_page(page);
last = btrfs_subpage_clear_and_test_dirty(fs_info, page, eb->start,
eb->len);
if (last)
btree_clear_page_dirty(page);
unlock_page(page);
WARN_ON(atomic_read(&eb->refs) == 0);
}
void btrfs_clear_buffer_dirty(struct btrfs_trans_handle *trans,
struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
int i;
int num_pages;
struct page *page;
btrfs_assert_tree_write_locked(eb);
if (trans && btrfs_header_generation(eb) != trans->transid)
return;
/*
* Instead of clearing the dirty flag off of the buffer, mark it as
* EXTENT_BUFFER_ZONED_ZEROOUT. This allows us to preserve
* write-ordering in zoned mode, without the need to later re-dirty
* the extent_buffer.
*
* The actual zeroout of the buffer will happen later in
* btree_csum_one_bio.
*/
if (btrfs_is_zoned(fs_info)) {
set_bit(EXTENT_BUFFER_ZONED_ZEROOUT, &eb->bflags);
return;
}
if (!test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags))
return;
percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, -eb->len,
fs_info->dirty_metadata_batch);
if (eb->fs_info->nodesize < PAGE_SIZE)
return clear_subpage_extent_buffer_dirty(eb);
num_pages = num_extent_pages(eb);
for (i = 0; i < num_pages; i++) {
page = eb->pages[i];
if (!PageDirty(page))
continue;
lock_page(page);
btree_clear_page_dirty(page);
unlock_page(page);
}
WARN_ON(atomic_read(&eb->refs) == 0);
}
void set_extent_buffer_dirty(struct extent_buffer *eb)
{
int i;
int num_pages;
bool was_dirty;
check_buffer_tree_ref(eb);
was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
num_pages = num_extent_pages(eb);
WARN_ON(atomic_read(&eb->refs) == 0);
WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
if (!was_dirty) {
bool subpage = eb->fs_info->nodesize < PAGE_SIZE;
/*
* For subpage case, we can have other extent buffers in the
* same page, and in clear_subpage_extent_buffer_dirty() we
* have to clear page dirty without subpage lock held.
* This can cause race where our page gets dirty cleared after
* we just set it.
*
* Thankfully, clear_subpage_extent_buffer_dirty() has locked
* its page for other reasons, we can use page lock to prevent
* the above race.
*/
if (subpage)
lock_page(eb->pages[0]);
for (i = 0; i < num_pages; i++)
btrfs_page_set_dirty(eb->fs_info, eb->pages[i],
eb->start, eb->len);
if (subpage)
unlock_page(eb->pages[0]);
percpu_counter_add_batch(&eb->fs_info->dirty_metadata_bytes,
eb->len,
eb->fs_info->dirty_metadata_batch);
}
#ifdef CONFIG_BTRFS_DEBUG
for (i = 0; i < num_pages; i++)
ASSERT(PageDirty(eb->pages[i]));
#endif
}
void clear_extent_buffer_uptodate(struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
struct page *page;
int num_pages;
int i;
clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
num_pages = num_extent_pages(eb);
for (i = 0; i < num_pages; i++) {
page = eb->pages[i];
if (!page)
continue;
/*
* This is special handling for metadata subpage, as regular
* btrfs_is_subpage() can not handle cloned/dummy metadata.
*/
if (fs_info->nodesize >= PAGE_SIZE)
ClearPageUptodate(page);
else
btrfs_subpage_clear_uptodate(fs_info, page, eb->start,
eb->len);
}
}
void set_extent_buffer_uptodate(struct extent_buffer *eb)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
struct page *page;
int num_pages;
int i;
set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
num_pages = num_extent_pages(eb);
for (i = 0; i < num_pages; i++) {
page = eb->pages[i];
/*
* This is special handling for metadata subpage, as regular
* btrfs_is_subpage() can not handle cloned/dummy metadata.
*/
if (fs_info->nodesize >= PAGE_SIZE)
SetPageUptodate(page);
else
btrfs_subpage_set_uptodate(fs_info, page, eb->start,
eb->len);
}
}
static void extent_buffer_read_end_io(struct btrfs_bio *bbio)
{
struct extent_buffer *eb = bbio->private;
struct btrfs_fs_info *fs_info = eb->fs_info;
bool uptodate = !bbio->bio.bi_status;
struct bvec_iter_all iter_all;
struct bio_vec *bvec;
u32 bio_offset = 0;
eb->read_mirror = bbio->mirror_num;
if (uptodate &&
btrfs_validate_extent_buffer(eb, &bbio->parent_check) < 0)
uptodate = false;
if (uptodate) {
set_extent_buffer_uptodate(eb);
} else {
clear_extent_buffer_uptodate(eb);
set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
}
bio_for_each_segment_all(bvec, &bbio->bio, iter_all) {
u64 start = eb->start + bio_offset;
struct page *page = bvec->bv_page;
u32 len = bvec->bv_len;
if (uptodate)
btrfs_page_set_uptodate(fs_info, page, start, len);
else
btrfs_page_clear_uptodate(fs_info, page, start, len);
bio_offset += len;
}
clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
smp_mb__after_atomic();
wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
free_extent_buffer(eb);
bio_put(&bbio->bio);
}
int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num,
struct btrfs_tree_parent_check *check)
{
int num_pages = num_extent_pages(eb), i;
struct btrfs_bio *bbio;
if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
return 0;
/*
* We could have had EXTENT_BUFFER_UPTODATE cleared by the write
* operation, which could potentially still be in flight. In this case
* we simply want to return an error.
*/
if (unlikely(test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags)))
return -EIO;
/* Someone else is already reading the buffer, just wait for it. */
if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags))
goto done;
clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
eb->read_mirror = 0;
check_buffer_tree_ref(eb);
atomic_inc(&eb->refs);
bbio = btrfs_bio_alloc(INLINE_EXTENT_BUFFER_PAGES,
REQ_OP_READ | REQ_META, eb->fs_info,
extent_buffer_read_end_io, eb);
bbio->bio.bi_iter.bi_sector = eb->start >> SECTOR_SHIFT;
bbio->inode = BTRFS_I(eb->fs_info->btree_inode);
bbio->file_offset = eb->start;
memcpy(&bbio->parent_check, check, sizeof(*check));
if (eb->fs_info->nodesize < PAGE_SIZE) {
__bio_add_page(&bbio->bio, eb->pages[0], eb->len,
eb->start - page_offset(eb->pages[0]));
} else {
for (i = 0; i < num_pages; i++)
__bio_add_page(&bbio->bio, eb->pages[i], PAGE_SIZE, 0);
}
btrfs_submit_bio(bbio, mirror_num);
done:
if (wait == WAIT_COMPLETE) {
wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_READING, TASK_UNINTERRUPTIBLE);
if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
return -EIO;
}
return 0;
}
static bool report_eb_range(const struct extent_buffer *eb, unsigned long start,
unsigned long len)
{
btrfs_warn(eb->fs_info,
"access to eb bytenr %llu len %lu out of range start %lu len %lu",
eb->start, eb->len, start, len);
WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
return true;
}
/*
* Check if the [start, start + len) range is valid before reading/writing
* the eb.
* NOTE: @start and @len are offset inside the eb, not logical address.
*
* Caller should not touch the dst/src memory if this function returns error.
*/
static inline int check_eb_range(const struct extent_buffer *eb,
unsigned long start, unsigned long len)
{
unsigned long offset;
/* start, start + len should not go beyond eb->len nor overflow */
if (unlikely(check_add_overflow(start, len, &offset) || offset > eb->len))
return report_eb_range(eb, start, len);
return false;
}
void read_extent_buffer(const struct extent_buffer *eb, void *dstv,
unsigned long start, unsigned long len)
{
size_t cur;
size_t offset;
struct page *page;
char *kaddr;
char *dst = (char *)dstv;
unsigned long i = get_eb_page_index(start);
if (check_eb_range(eb, start, len)) {
/*
* Invalid range hit, reset the memory, so callers won't get
* some random garbage for their uninitialized memory.
*/
memset(dstv, 0, len);
return;
}
if (eb->addr) {
memcpy(dstv, eb->addr + start, len);
return;
}
offset = get_eb_offset_in_page(eb, start);
while (len > 0) {
page = eb->pages[i];
cur = min(len, (PAGE_SIZE - offset));
kaddr = page_address(page);
memcpy(dst, kaddr + offset, cur);
dst += cur;
len -= cur;
offset = 0;
i++;
}
}
int read_extent_buffer_to_user_nofault(const struct extent_buffer *eb,
void __user *dstv,
unsigned long start, unsigned long len)
{
size_t cur;
size_t offset;
struct page *page;
char *kaddr;
char __user *dst = (char __user *)dstv;
unsigned long i = get_eb_page_index(start);
int ret = 0;
WARN_ON(start > eb->len);
WARN_ON(start + len > eb->start + eb->len);
if (eb->addr) {
if (copy_to_user_nofault(dstv, eb->addr + start, len))
ret = -EFAULT;
return ret;
}
offset = get_eb_offset_in_page(eb, start);
while (len > 0) {
page = eb->pages[i];
cur = min(len, (PAGE_SIZE - offset));
kaddr = page_address(page);
if (copy_to_user_nofault(dst, kaddr + offset, cur)) {
ret = -EFAULT;
break;
}
dst += cur;
len -= cur;
offset = 0;
i++;
}
return ret;
}
int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
unsigned long start, unsigned long len)
{
size_t cur;
size_t offset;
struct page *page;
char *kaddr;
char *ptr = (char *)ptrv;
unsigned long i = get_eb_page_index(start);
int ret = 0;
if (check_eb_range(eb, start, len))
return -EINVAL;
if (eb->addr)
return memcmp(ptrv, eb->addr + start, len);
offset = get_eb_offset_in_page(eb, start);
while (len > 0) {
page = eb->pages[i];
cur = min(len, (PAGE_SIZE - offset));
kaddr = page_address(page);
ret = memcmp(ptr, kaddr + offset, cur);
if (ret)
break;
ptr += cur;
len -= cur;
offset = 0;
i++;
}
return ret;
}
/*
* Check that the extent buffer is uptodate.
*
* For regular sector size == PAGE_SIZE case, check if @page is uptodate.
* For subpage case, check if the range covered by the eb has EXTENT_UPTODATE.
*/
static void assert_eb_page_uptodate(const struct extent_buffer *eb,
struct page *page)
{
struct btrfs_fs_info *fs_info = eb->fs_info;
/*
* If we are using the commit root we could potentially clear a page
* Uptodate while we're using the extent buffer that we've previously
* looked up. We don't want to complain in this case, as the page was
* valid before, we just didn't write it out. Instead we want to catch
* the case where we didn't actually read the block properly, which
* would have !PageUptodate and !EXTENT_BUFFER_WRITE_ERR.
*/
if (test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))
return;
if (fs_info->nodesize < PAGE_SIZE) {
if (WARN_ON(!btrfs_subpage_test_uptodate(fs_info, page,
eb->start, eb->len)))
btrfs_subpage_dump_bitmap(fs_info, page, eb->start, eb->len);
} else {
WARN_ON(!PageUptodate(page));
}
}
static void __write_extent_buffer(const struct extent_buffer *eb,
const void *srcv, unsigned long start,
unsigned long len, bool use_memmove)
{
size_t cur;
size_t offset;
struct page *page;
char *kaddr;
char *src = (char *)srcv;
unsigned long i = get_eb_page_index(start);
/* For unmapped (dummy) ebs, no need to check their uptodate status. */
const bool check_uptodate = !test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags);
if (check_eb_range(eb, start, len))
return;
if (eb->addr) {
if (use_memmove)
memmove(eb->addr + start, srcv, len);
else
memcpy(eb->addr + start, srcv, len);
return;
}
offset = get_eb_offset_in_page(eb, start);
while (len > 0) {
page = eb->pages[i];
if (check_uptodate)
assert_eb_page_uptodate(eb, page);
cur = min(len, PAGE_SIZE - offset);
kaddr = page_address(page);
if (use_memmove)
memmove(kaddr + offset, src, cur);
else
memcpy(kaddr + offset, src, cur);
src += cur;
len -= cur;
offset = 0;
i++;
}
}
void write_extent_buffer(const struct extent_buffer *eb, const void *srcv,
unsigned long start, unsigned long len)
{
return __write_extent_buffer(eb, srcv, start, len, false);
}
static void memset_extent_buffer(const struct extent_buffer *eb, int c,
unsigned long start, unsigned long len)
{
unsigned long cur = start;
if (eb->addr) {
memset(eb->addr + start, c, len);
return;
}
while (cur < start + len) {
unsigned long index = get_eb_page_index(cur);
unsigned int offset = get_eb_offset_in_page(eb, cur);
unsigned int cur_len = min(start + len - cur, PAGE_SIZE - offset);
struct page *page = eb->pages[index];
assert_eb_page_uptodate(eb, page);
memset_page(page, offset, c, cur_len);
cur += cur_len;
}
}
void memzero_extent_buffer(const struct extent_buffer *eb, unsigned long start,
unsigned long len)
{
if (check_eb_range(eb, start, len))
return;
return memset_extent_buffer(eb, 0, start, len);
}
void copy_extent_buffer_full(const struct extent_buffer *dst,
const struct extent_buffer *src)
{
unsigned long cur = 0;
ASSERT(dst->len == src->len);
while (cur < src->len) {
unsigned long index = get_eb_page_index(cur);
unsigned long offset = get_eb_offset_in_page(src, cur);
unsigned long cur_len = min(src->len, PAGE_SIZE - offset);
void *addr = page_address(src->pages[index]) + offset;
write_extent_buffer(dst, addr, cur, cur_len);
cur += cur_len;
}
}
void copy_extent_buffer(const struct extent_buffer *dst,
const struct extent_buffer *src,
unsigned long dst_offset, unsigned long src_offset,
unsigned long len)
{
u64 dst_len = dst->len;
size_t cur;
size_t offset;
struct page *page;
char *kaddr;
unsigned long i = get_eb_page_index(dst_offset);
if (check_eb_range(dst, dst_offset, len) ||
check_eb_range(src, src_offset, len))
return;
WARN_ON(src->len != dst_len);
offset = get_eb_offset_in_page(dst, dst_offset);
while (len > 0) {
page = dst->pages[i];
assert_eb_page_uptodate(dst, page);
cur = min(len, (unsigned long)(PAGE_SIZE - offset));
kaddr = page_address(page);
read_extent_buffer(src, kaddr + offset, src_offset, cur);
src_offset += cur;
len -= cur;
offset = 0;
i++;
}
}
/*
* Calculate the page and offset of the byte containing the given bit number.
*
* @eb: the extent buffer
* @start: offset of the bitmap item in the extent buffer
* @nr: bit number
* @page_index: return index of the page in the extent buffer that contains
* the given bit number
* @page_offset: return offset into the page given by page_index
*
* This helper hides the ugliness of finding the byte in an extent buffer which
* contains a given bit.
*/
static inline void eb_bitmap_offset(const struct extent_buffer *eb,
unsigned long start, unsigned long nr,
unsigned long *page_index,
size_t *page_offset)
{
size_t byte_offset = BIT_BYTE(nr);
size_t offset;
/*
* The byte we want is the offset of the extent buffer + the offset of
* the bitmap item in the extent buffer + the offset of the byte in the
* bitmap item.
*/
offset = start + offset_in_page(eb->start) + byte_offset;
*page_index = offset >> PAGE_SHIFT;
*page_offset = offset_in_page(offset);
}
/*
* Determine whether a bit in a bitmap item is set.
*
* @eb: the extent buffer
* @start: offset of the bitmap item in the extent buffer
* @nr: bit number to test
*/
int extent_buffer_test_bit(const struct extent_buffer *eb, unsigned long start,
unsigned long nr)
{
u8 *kaddr;
struct page *page;
unsigned long i;
size_t offset;
eb_bitmap_offset(eb, start, nr, &i, &offset);
page = eb->pages[i];
assert_eb_page_uptodate(eb, page);
kaddr = page_address(page);
return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
}
static u8 *extent_buffer_get_byte(const struct extent_buffer *eb, unsigned long bytenr)
{
unsigned long index = get_eb_page_index(bytenr);
if (check_eb_range(eb, bytenr, 1))
return NULL;
return page_address(eb->pages[index]) + get_eb_offset_in_page(eb, bytenr);
}
/*
* Set an area of a bitmap to 1.
*
* @eb: the extent buffer
* @start: offset of the bitmap item in the extent buffer
* @pos: bit number of the first bit
* @len: number of bits to set
*/
void extent_buffer_bitmap_set(const struct extent_buffer *eb, unsigned long start,
unsigned long pos, unsigned long len)
{
unsigned int first_byte = start + BIT_BYTE(pos);
unsigned int last_byte = start + BIT_BYTE(pos + len - 1);
const bool same_byte = (first_byte == last_byte);
u8 mask = BITMAP_FIRST_BYTE_MASK(pos);
u8 *kaddr;
if (same_byte)
mask &= BITMAP_LAST_BYTE_MASK(pos + len);
/* Handle the first byte. */
kaddr = extent_buffer_get_byte(eb, first_byte);
*kaddr |= mask;
if (same_byte)
return;
/* Handle the byte aligned part. */
ASSERT(first_byte + 1 <= last_byte);
memset_extent_buffer(eb, 0xff, first_byte + 1, last_byte - first_byte - 1);
/* Handle the last byte. */
kaddr = extent_buffer_get_byte(eb, last_byte);
*kaddr |= BITMAP_LAST_BYTE_MASK(pos + len);
}
/*
* Clear an area of a bitmap.
*
* @eb: the extent buffer
* @start: offset of the bitmap item in the extent buffer
* @pos: bit number of the first bit
* @len: number of bits to clear
*/
void extent_buffer_bitmap_clear(const struct extent_buffer *eb,
unsigned long start, unsigned long pos,
unsigned long len)
{
unsigned int first_byte = start + BIT_BYTE(pos);
unsigned int last_byte = start + BIT_BYTE(pos + len - 1);
const bool same_byte = (first_byte == last_byte);
u8 mask = BITMAP_FIRST_BYTE_MASK(pos);
u8 *kaddr;
if (same_byte)
mask &= BITMAP_LAST_BYTE_MASK(pos + len);
/* Handle the first byte. */
kaddr = extent_buffer_get_byte(eb, first_byte);
*kaddr &= ~mask;
if (same_byte)
return;
/* Handle the byte aligned part. */
ASSERT(first_byte + 1 <= last_byte);
memset_extent_buffer(eb, 0, first_byte + 1, last_byte - first_byte - 1);
/* Handle the last byte. */
kaddr = extent_buffer_get_byte(eb, last_byte);
*kaddr &= ~BITMAP_LAST_BYTE_MASK(pos + len);
}
static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)
{
unsigned long distance = (src > dst) ? src - dst : dst - src;
return distance < len;
}
void memcpy_extent_buffer(const struct extent_buffer *dst,
unsigned long dst_offset, unsigned long src_offset,
unsigned long len)
{
unsigned long cur_off = 0;
if (check_eb_range(dst, dst_offset, len) ||
check_eb_range(dst, src_offset, len))
return;
if (dst->addr) {
const bool use_memmove = areas_overlap(src_offset, dst_offset, len);
if (use_memmove)
memmove(dst->addr + dst_offset, dst->addr + src_offset, len);
else
memcpy(dst->addr + dst_offset, dst->addr + src_offset, len);
return;
}
while (cur_off < len) {
unsigned long cur_src = cur_off + src_offset;
unsigned long pg_index = get_eb_page_index(cur_src);
unsigned long pg_off = get_eb_offset_in_page(dst, cur_src);
unsigned long cur_len = min(src_offset + len - cur_src,
PAGE_SIZE - pg_off);
void *src_addr = page_address(dst->pages[pg_index]) + pg_off;
const bool use_memmove = areas_overlap(src_offset + cur_off,
dst_offset + cur_off, cur_len);
__write_extent_buffer(dst, src_addr, dst_offset + cur_off, cur_len,
use_memmove);
cur_off += cur_len;
}
}
void memmove_extent_buffer(const struct extent_buffer *dst,
unsigned long dst_offset, unsigned long src_offset,
unsigned long len)
{
unsigned long dst_end = dst_offset + len - 1;
unsigned long src_end = src_offset + len - 1;
if (check_eb_range(dst, dst_offset, len) ||
check_eb_range(dst, src_offset, len))
return;
if (dst_offset < src_offset) {
memcpy_extent_buffer(dst, dst_offset, src_offset, len);
return;
}
if (dst->addr) {
memmove(dst->addr + dst_offset, dst->addr + src_offset, len);
return;
}
while (len > 0) {
unsigned long src_i;
size_t cur;
size_t dst_off_in_page;
size_t src_off_in_page;
void *src_addr;
bool use_memmove;
src_i = get_eb_page_index(src_end);
dst_off_in_page = get_eb_offset_in_page(dst, dst_end);
src_off_in_page = get_eb_offset_in_page(dst, src_end);
cur = min_t(unsigned long, len, src_off_in_page + 1);
cur = min(cur, dst_off_in_page + 1);
src_addr = page_address(dst->pages[src_i]) + src_off_in_page -
cur + 1;
use_memmove = areas_overlap(src_end - cur + 1, dst_end - cur + 1,
cur);
__write_extent_buffer(dst, src_addr, dst_end - cur + 1, cur,
use_memmove);
dst_end -= cur;
src_end -= cur;
len -= cur;
}
}
#define GANG_LOOKUP_SIZE 16
static struct extent_buffer *get_next_extent_buffer(
struct btrfs_fs_info *fs_info, struct page *page, u64 bytenr)
{
struct extent_buffer *gang[GANG_LOOKUP_SIZE];
struct extent_buffer *found = NULL;
u64 page_start = page_offset(page);
u64 cur = page_start;
ASSERT(in_range(bytenr, page_start, PAGE_SIZE));
lockdep_assert_held(&fs_info->buffer_lock);
while (cur < page_start + PAGE_SIZE) {
int ret;
int i;
ret = radix_tree_gang_lookup(&fs_info->buffer_radix,
(void **)gang, cur >> fs_info->sectorsize_bits,
min_t(unsigned int, GANG_LOOKUP_SIZE,
PAGE_SIZE / fs_info->nodesize));
if (ret == 0)
goto out;
for (i = 0; i < ret; i++) {
/* Already beyond page end */
if (gang[i]->start >= page_start + PAGE_SIZE)
goto out;
/* Found one */
if (gang[i]->start >= bytenr) {
found = gang[i];
goto out;
}
}
cur = gang[ret - 1]->start + gang[ret - 1]->len;
}
out:
return found;
}
static int try_release_subpage_extent_buffer(struct page *page)
{
struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb);
u64 cur = page_offset(page);
const u64 end = page_offset(page) + PAGE_SIZE;
int ret;
while (cur < end) {
struct extent_buffer *eb = NULL;
/*
* Unlike try_release_extent_buffer() which uses folio private
* to grab buffer, for subpage case we rely on radix tree, thus
* we need to ensure radix tree consistency.
*
* We also want an atomic snapshot of the radix tree, thus go
* with spinlock rather than RCU.
*/
spin_lock(&fs_info->buffer_lock);
eb = get_next_extent_buffer(fs_info, page, cur);
if (!eb) {
/* No more eb in the page range after or at cur */
spin_unlock(&fs_info->buffer_lock);
break;
}
cur = eb->start + eb->len;
/*
* The same as try_release_extent_buffer(), to ensure the eb
* won't disappear out from under us.
*/
spin_lock(&eb->refs_lock);
if (atomic_read(&eb->refs) != 1 || extent_buffer_under_io(eb)) {
spin_unlock(&eb->refs_lock);
spin_unlock(&fs_info->buffer_lock);
break;
}
spin_unlock(&fs_info->buffer_lock);
/*
* If tree ref isn't set then we know the ref on this eb is a
* real ref, so just return, this eb will likely be freed soon
* anyway.
*/
if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
spin_unlock(&eb->refs_lock);
break;
}
/*
* Here we don't care about the return value, we will always
* check the folio private at the end. And
* release_extent_buffer() will release the refs_lock.
*/
release_extent_buffer(eb);
}
/*
* Finally to check if we have cleared folio private, as if we have
* released all ebs in the page, the folio private should be cleared now.
*/
spin_lock(&page->mapping->private_lock);
if (!folio_test_private(page_folio(page)))
ret = 1;
else
ret = 0;
spin_unlock(&page->mapping->private_lock);
return ret;
}
int try_release_extent_buffer(struct page *page)
{
struct folio *folio = page_folio(page);
struct extent_buffer *eb;
if (btrfs_sb(page->mapping->host->i_sb)->nodesize < PAGE_SIZE)
return try_release_subpage_extent_buffer(page);
/*
* We need to make sure nobody is changing folio private, as we rely on
* folio private as the pointer to extent buffer.
*/
spin_lock(&page->mapping->private_lock);
if (!folio_test_private(folio)) {
spin_unlock(&page->mapping->private_lock);
return 1;
}
eb = folio_get_private(folio);
BUG_ON(!eb);
/*
* This is a little awful but should be ok, we need to make sure that
* the eb doesn't disappear out from under us while we're looking at
* this page.
*/
spin_lock(&eb->refs_lock);
if (atomic_read(&eb->refs) != 1 || extent_buffer_under_io(eb)) {
spin_unlock(&eb->refs_lock);
spin_unlock(&page->mapping->private_lock);
return 0;
}
spin_unlock(&page->mapping->private_lock);
/*
* If tree ref isn't set then we know the ref on this eb is a real ref,
* so just return, this page will likely be freed soon anyway.
*/
if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
spin_unlock(&eb->refs_lock);
return 0;
}
return release_extent_buffer(eb);
}
/*
* Attempt to readahead a child block.
*
* @fs_info: the fs_info
* @bytenr: bytenr to read
* @owner_root: objectid of the root that owns this eb
* @gen: generation for the uptodate check, can be 0
* @level: level for the eb
*
* Attempt to readahead a tree block at @bytenr. If @gen is 0 then we do a
* normal uptodate check of the eb, without checking the generation. If we have
* to read the block we will not block on anything.
*/
void btrfs_readahead_tree_block(struct btrfs_fs_info *fs_info,
u64 bytenr, u64 owner_root, u64 gen, int level)
{
struct btrfs_tree_parent_check check = {
.has_first_key = 0,
.level = level,
.transid = gen
};
struct extent_buffer *eb;
int ret;
eb = btrfs_find_create_tree_block(fs_info, bytenr, owner_root, level);
if (IS_ERR(eb))
return;
if (btrfs_buffer_uptodate(eb, gen, 1)) {
free_extent_buffer(eb);
return;
}
ret = read_extent_buffer_pages(eb, WAIT_NONE, 0, &check);
if (ret < 0)
free_extent_buffer_stale(eb);
else
free_extent_buffer(eb);
}
/*
* Readahead a node's child block.
*
* @node: parent node we're reading from
* @slot: slot in the parent node for the child we want to read
*
* A helper for btrfs_readahead_tree_block, we simply read the bytenr pointed at
* the slot in the node provided.
*/
void btrfs_readahead_node_child(struct extent_buffer *node, int slot)
{
btrfs_readahead_tree_block(node->fs_info,
btrfs_node_blockptr(node, slot),
btrfs_header_owner(node),
btrfs_node_ptr_generation(node, slot),
btrfs_header_level(node) - 1);
}
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