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author | Christoph Hellwig <hch@lst.de> | 2017-02-06 13:00:54 -0800 |
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committer | Darrick J. Wong <darrick.wong@oracle.com> | 2017-02-06 17:47:46 -0800 |
commit | 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e (patch) | |
tree | 47f55c2f61169e2774cd73770c2237ff9356a5ec /fs/xfs/xfs_file.c | |
parent | 4dd2eb633598cb6a5a0be2fd9a2be0819f5eeb5f (diff) | |
download | linux-54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e.tar.gz linux-54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e.tar.bz2 linux-54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e.zip |
xfs: reject all unaligned direct writes to reflinked files
We currently fall back from direct to buffered writes if we detect a
remaining shared extent in the iomap_begin callback. But by the time
iomap_begin is called for the potentially unaligned end block we might
have already written most of the data to disk, which we'd now write
again using buffered I/O. To avoid this reject all writes to reflinked
files before starting I/O so that we are guaranteed to only write the
data once.
The alternative would be to unshare the unaligned start and/or end block
before doing the I/O. I think that's doable, and will actually be
required to support reflinks on DAX file system. But it will take a
little more time and I'd rather get rid of the double write ASAP.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/xfs/xfs_file.c')
-rw-r--r-- | fs/xfs/xfs_file.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 032c8a74824a..2a695a8f4fe7 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -527,6 +527,15 @@ xfs_file_dio_aio_write( if ((iocb->ki_pos & mp->m_blockmask) || ((iocb->ki_pos + count) & mp->m_blockmask)) { unaligned_io = 1; + + /* + * We can't properly handle unaligned direct I/O to reflink + * files yet, as we can't unshare a partial block. + */ + if (xfs_is_reflink_inode(ip)) { + trace_xfs_reflink_bounce_dio_write(ip, iocb->ki_pos, count); + return -EREMCHG; + } iolock = XFS_IOLOCK_EXCL; } else { iolock = XFS_IOLOCK_SHARED; |