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iomap/gfs2: Unlock and put folio in page_done handler

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When an iomap defines a ->page_done() handler in its page_ops, delegate
unlocking the folio and putting the folio reference to that handler.

This allows to fix a race between journaled data writes and folio
writeback in gfs2: before this change, gfs2_iomap_page_done() was called
after unlocking the folio, so writeback could start writing back the
folio's buffers before they could be marked for writing to the journal.
Also, try_to_free_buffers() could free the buffers before
gfs2_iomap_page_done() was done adding the buffers to the current
current transaction.  With this change, gfs2_iomap_page_done() adds the
buffers to the current transaction while the folio is still locked, so
the problems described above can no longer occur.

The only current user of ->page_done() is gfs2, so other filesystems are
not affected.  To catch out any out-of-tree users, switch from a page to
a folio in ->page_done().

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Andreas Gruenbacher 2023-01-15 08:45:51 -08:00 committed by Darrick J. Wong
parent 7a70a5085e
commit 80baab88bb
3 changed files with 20 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
fs/gfs2/bmap.c
View File

@ -968,14 +968,23 @@ static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos,
}
static void gfs2_iomap_page_done(struct inode *inode, loff_t pos,
unsigned copied, struct page *page)
unsigned copied, struct folio *folio)
{
struct gfs2_trans *tr = current->journal_info;
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);
if (page && !gfs2_is_stuffed(ip))
gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied);
if (!folio) {
gfs2_trans_end(sdp);
return;
}
if (!gfs2_is_stuffed(ip))
gfs2_page_add_databufs(ip, &folio->page, offset_in_page(pos),
copied);
folio_unlock(folio);
folio_put(folio);
if (tr->tr_num_buf_new)
__mark_inode_dirty(inode, I_DIRTY_DATASYNC);

8
fs/iomap/buffered-io.c
View File

@ -580,12 +580,12 @@ static void __iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret,
{
const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
if (folio)
if (page_ops && page_ops->page_done) {
page_ops->page_done(iter->inode, pos, ret, folio);
} else if (folio) {
folio_unlock(folio);
if (page_ops && page_ops->page_done)
page_ops->page_done(iter->inode, pos, ret, &folio->page);
if (folio)
folio_put(folio);
}
}
static int iomap_write_begin_inline(const struct iomap_iter *iter,

7
include/linux/iomap.h
View File

@ -131,13 +131,14 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap)
* associated with them.
*
* When page_prepare succeeds, page_done will always be called to do any
* cleanup work necessary. In that page_done call, @page will be NULL if the
* associated page could not be obtained.
* cleanup work necessary. In that page_done call, @folio will be NULL if the
* associated folio could not be obtained. When folio is not NULL, page_done
* is responsible for unlocking and putting the folio.
*/
struct iomap_page_ops {
int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len);
void (*page_done)(struct inode *inode, loff_t pos, unsigned copied,
struct page *page);
struct folio *folio);
/*
* Check that the cached iomap still maps correctly to the filesystem's