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linux/fs/xfs/xfs_reflink.h

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xfs: introduce the CoW fork Introduce a new in-core fork for storing copy-on-write delalloc reservations and allocated extents that are in the process of being written out. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:32 +03:00
/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
*
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef __XFS_REFLINK_H
#define __XFS_REFLINK_H 1
xfs: create delalloc extents in CoW fork Wire up iomap_begin to detect shared extents and create delayed allocation extents in the CoW fork: 1) Check if we already have an extent in the COW fork for the area. If so nothing to do, we can move along. 2) Look up block number for the current extent, and if there is none it's not shared move along. 3) Unshare the current extent as far as we are going to write into it. For this we avoid an additional COW fork lookup and use the information we set aside in step 1) above. 4) Goto 1) unless we've covered the whole range. Last but not least, this updates the xfs_reflink_reserve_cow_range calling convention to pass a byte offset and length, as that is what both callers expect anyway. This patch has been refactored considerably as part of the iomap transition. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:33 +03:00
extern int xfs_reflink_find_shared(struct xfs_mount *mp, xfs_agnumber_t agno,
xfs_agblock_t agbno, xfs_extlen_t aglen, xfs_agblock_t *fbno,
xfs_extlen_t *flen, bool find_maximal);
extern int xfs_reflink_trim_around_shared(struct xfs_inode *ip,
struct xfs_bmbt_irec *irec, bool *shared, bool *trimmed);
xfs: optimize writes to reflink files Instead of reserving space as the first thing in write_begin move it past reading the extent in the data fork. That way we only have to read from the data fork once and can reuse that information for trimming the extent to the shared/unshared boundary. Additionally this allows to easily limit the actual write size to said boundary, and avoid a roundtrip on the ilock. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2016-10-20 07:53:50 +03:00
extern int xfs_reflink_reserve_cow(struct xfs_inode *ip,
struct xfs_bmbt_irec *imap, bool *shared);
xfs: allocate direct I/O COW blocks in iomap_begin Instead of preallocating all the required COW blocks in the high-level write code do it inside the iomap code, like we do for all other I/O. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2017-02-06 21:51:03 +03:00
extern int xfs_reflink_allocate_cow(struct xfs_inode *ip,
struct xfs_bmbt_irec *imap, bool *shared, uint *lockmode);
xfs: mark speculative prealloc CoW fork extents unwritten Christoph Hellwig pointed out that there's a potentially nasty race when performing simultaneous nearby directio cow writes: "Thread 1 writes a range from B to c " B --------- C p "a little later thread 2 writes from A to B " A --------- B p [editor's note: the 'p' denote cowextsize boundaries, which I added to make this more clear] "but the code preallocates beyond B into the range where thread "1 has just written, but ->end_io hasn't been called yet. "But once ->end_io is called thread 2 has already allocated "up to the extent size hint into the write range of thread 1, "so the end_io handler will splice the unintialized blocks from "that preallocation back into the file right after B." We can avoid this race by ensuring that thread 1 cannot accidentally remap the blocks that thread 2 allocated (as part of speculative preallocation) as part of t2's write preparation in t1's end_io handler. The way we make this happen is by taking advantage of the unwritten extent flag as an intermediate step. Recall that when we begin the process of writing data to shared blocks, we create a delayed allocation extent in the CoW fork: D: --RRRRRRSSSRRRRRRRR--- C: ------DDDDDDD--------- When a thread prepares to CoW some dirty data out to disk, it will now convert the delalloc reservation into an /unwritten/ allocated extent in the cow fork. The da conversion code tries to opportunistically allocate as much of a (speculatively prealloc'd) extent as possible, so we may end up allocating a larger extent than we're actually writing out: D: --RRRRRRSSSRRRRRRRR--- U: ------UUUUUUU--------- Next, we convert only the part of the extent that we're actively planning to write to normal (i.e. not unwritten) status: D: --RRRRRRSSSRRRRRRRR--- U: ------UURRUUU--------- If the write succeeds, the end_cow function will now scan the relevant range of the CoW fork for real extents and remap only the real extents into the data fork: D: --RRRRRRRRSRRRRRRRR--- U: ------UU--UUU--------- This ensures that we never obliterate valid data fork extents with unwritten blocks from the CoW fork. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2017-02-03 02:14:02 +03:00
extern int xfs_reflink_convert_cow(struct xfs_inode *ip, xfs_off_t offset,
xfs_off_t count);
xfs: allocate delayed extents in CoW fork Modify the writepage handler to find and convert pending delalloc extents to real allocations. Furthermore, when we're doing non-cow writes to a part of a file that already has a CoW reservation (the cowextsz hint that we set up in a subsequent patch facilitates this), promote the write to copy-on-write so that the entire extent can get written out as a single extent on disk, thereby reducing post-CoW fragmentation. Christoph moved the CoW support code in _map_blocks to a separate helper function, refactored other functions, and reduced the number of CoW fork lookups, so I merged those changes here to reduce churn. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:34 +03:00
extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
xfs: cleanup xfs_reflink_find_cow_mapping Use xfs_iext_lookup_extent to look up the extent, drop a useless check, drop a unneeded return value and clean up the general style a little bit. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2016-11-24 03:39:49 +03:00
struct xfs_bmbt_irec *imap);
xfs: use new extent lookup helpers in xfs_reflink_trim_irec_to_next_cow And remove the unused return value. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2016-11-24 03:39:50 +03:00
extern void xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
xfs: allocate delayed extents in CoW fork Modify the writepage handler to find and convert pending delalloc extents to real allocations. Furthermore, when we're doing non-cow writes to a part of a file that already has a CoW reservation (the cowextsz hint that we set up in a subsequent patch facilitates this), promote the write to copy-on-write so that the entire extent can get written out as a single extent on disk, thereby reducing post-CoW fragmentation. Christoph moved the CoW support code in _map_blocks to a separate helper function, refactored other functions, and reduced the number of CoW fork lookups, so I merged those changes here to reduce churn. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:34 +03:00
xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap);
xfs: create delalloc extents in CoW fork Wire up iomap_begin to detect shared extents and create delayed allocation extents in the CoW fork: 1) Check if we already have an extent in the COW fork for the area. If so nothing to do, we can move along. 2) Look up block number for the current extent, and if there is none it's not shared move along. 3) Unshare the current extent as far as we are going to write into it. For this we avoid an additional COW fork lookup and use the information we set aside in step 1) above. 4) Goto 1) unless we've covered the whole range. Last but not least, this updates the xfs_reflink_reserve_cow_range calling convention to pass a byte offset and length, as that is what both callers expect anyway. This patch has been refactored considerably as part of the iomap transition. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:33 +03:00
xfs: move mappings from cow fork to data fork after copy-write After the write component of a copy-write operation finishes, clean up the bookkeeping left behind. On error, we simply free the new blocks and pass the error up. If we succeed, however, then we must remove the old data fork mapping and move the cow fork mapping to the data fork. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> [hch: Call the CoW failure function during xfs_cancel_ioend] Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:35 +03:00
extern int xfs_reflink_cancel_cow_blocks(struct xfs_inode *ip,
struct xfs_trans **tpp, xfs_fileoff_t offset_fsb,
xfs_fileoff_t end_fsb);
extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset,
xfs_off_t count);
extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,
xfs_off_t count);
xfs: store in-progress CoW allocations in the refcount btree Due to the way the CoW algorithm in XFS works, there's an interval during which blocks allocated to handle a CoW can be lost -- if the FS goes down after the blocks are allocated but before the block remapping takes place. This is exacerbated by the cowextsz hint -- allocated reservations can sit around for a while, waiting to get used. Since the refcount btree doesn't normally store records with refcount of 1, we can use it to record these in-progress extents. In-progress blocks cannot be shared because they're not user-visible, so there shouldn't be any conflicts with other programs. This is a better solution than holding EFIs during writeback because (a) EFIs can't be relogged currently, (b) even if they could, EFIs are bound by available log space, which puts an unnecessary upper bound on how much CoW we can have in flight, and (c) we already have a mechanism to track blocks. At mount time, read the refcount records and free anything we find with a refcount of 1 because those were in-progress when the FS went down. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:39 +03:00
extern int xfs_reflink_recover_cow(struct xfs_mount *mp);
xfs: merge xfs_reflink_remap_range and xfs_file_share_range There is no clear division of responsibility between those functions, so just merge them into one to keep the code simple. Also move xfs_file_wait_for_io to xfs_reflink.c together with its only caller. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2016-10-20 07:50:07 +03:00
extern int xfs_reflink_remap_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, u64 len, bool is_dedupe);
xfs: unshare a range of blocks via fallocate Unshare all shared extents if the user calls fallocate with the new unshare mode flag set, so that we can guarantee that a subsequent write will not ENOSPC. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> [hch: pass inode instead of file to xfs_reflink_dirty_range, use iomap infrastructure for copy up] Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:43 +03:00
extern int xfs_reflink_clear_inode_flag(struct xfs_inode *ip,
struct xfs_trans **tpp);
extern int xfs_reflink_unshare(struct xfs_inode *ip, xfs_off_t offset,
xfs_off_t len);
xfs: move mappings from cow fork to data fork after copy-write After the write component of a copy-write operation finishes, clean up the bookkeeping left behind. On error, we simply free the new blocks and pass the error up. If we succeed, however, then we must remove the old data fork mapping and move the cow fork mapping to the data fork. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> [hch: Call the CoW failure function during xfs_cancel_ioend] Signed-off-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:35 +03:00
xfs: introduce the CoW fork Introduce a new in-core fork for storing copy-on-write delalloc reservations and allocated extents that are in the process of being written out. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2016-10-03 19:11:32 +03:00
#endif /* __XFS_REFLINK_H */
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