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iomap: iomap that extends beyond EOF should be marked dirty

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When doing a direct IO that spans the current EOF, and there are
written blocks beyond EOF that extend beyond the current write, the
only metadata update that needs to be done is a file size extension.

However, we don't mark such iomaps as IOMAP_F_DIRTY to indicate that
there is IO completion metadata updates required, and hence we may
fail to correctly sync file size extensions made in IO completion
when O_DSYNC writes are being used and the hardware supports FUA.

Hence when setting IOMAP_F_DIRTY, we need to also take into account
whether the iomap spans the current EOF. If it does, then we need to
mark it dirty so that IO completion will call generic_write_sync()
to flush the inode size update to stable storage correctly.

Fixes: 3460cac1ca ("iomap: Use FUA for pure data O_DSYNC DIO writes")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: removed the ext4 part; they'll handle it separately]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Dave Chinner 2019-10-17 13:12:01 -07:00 committed by Darrick J. Wong
parent 906753befc
commit 7684e2c438
2 changed files with 9 additions and 0 deletions
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7
fs/xfs/xfs_iomap.c
View File

@ -1049,6 +1049,13 @@ xfs_file_iomap_begin(
trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
out_finish:
/*
* Writes that span EOF might trigger an IO size update on completion,
* so consider them to be dirty for the purposes of O_DSYNC even if
* there is no other metadata changes pending or have been made here.
*/
if ((flags & IOMAP_WRITE) && offset + length > i_size_read(inode))
iomap->flags |= IOMAP_F_DIRTY;
return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
out_found:

2
include/linux/iomap.h
View File

@ -32,6 +32,8 @@ struct vm_fault;
*
* IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
* written data and requires fdatasync to commit them to persistent storage.
* This needs to take into account metadata changes that *may* be made at IO
* completion, such as file size updates from direct IO.
*/
#define IOMAP_F_NEW 0x01 /* blocks have been newly allocated */
#define IOMAP_F_DIRTY 0x02 /* uncommitted metadata */