xfs: use iomap_valid method to detect stale cached iomaps

Now that iomap supports a mechanism to validate cached iomaps for
buffered write operations, hook it up to the XFS buffered write ops
so that we can avoid data corruptions that result from stale cached
iomaps. See:

https://lore.kernel.org/linux-xfs/20220817093627.GZ3600936@dread.disaster.area/

or the ->iomap_valid() introduction commit for exact details of the
corruption vector.

The validity cookie we store in the iomap is based on the type of
iomap we return. It is expected that the iomap->flags we set in
xfs_bmbt_to_iomap() is not perturbed by the iomap core and are
returned to us in the iomap passed via the .iomap_valid() callback.
This ensures that the validity cookie is always checking the correct
inode fork sequence numbers to detect potential changes that affect
the extent cached by the iomap.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index 0f62ab633040..4da13440bae9 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -13,14 +13,15 @@ struct xfs_bmbt_irec;
 
 int xfs_iomap_write_direct(struct xfs_inode *ip, xfs_fileoff_t offset_fsb,
 		xfs_fileoff_t count_fsb, unsigned int flags,
-		struct xfs_bmbt_irec *imap);
+		struct xfs_bmbt_irec *imap, u64 *sequence);
 int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
 xfs_fileoff_t xfs_iomap_eof_align_last_fsb(struct xfs_inode *ip,
 		xfs_fileoff_t end_fsb);
 
+u64 xfs_iomap_inode_sequence(struct xfs_inode *ip, u16 iomap_flags);
 int xfs_bmbt_to_iomap(struct xfs_inode *ip, struct iomap *iomap,
 		struct xfs_bmbt_irec *imap, unsigned int mapping_flags,
-		u16 iomap_flags);
+		u16 iomap_flags, u64 sequence_cookie);
 
 int xfs_zero_range(struct xfs_inode *ip, loff_t pos, loff_t len,
 		bool *did_zero);