diff options
author | Christoph Hellwig <hch@lst.de> | 2017-02-06 21:00:54 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-04-08 07:30:31 (GMT) |
commit | 5bbf5ba693ac6dc323d6608740311c34b978e986 (patch) | |
tree | aec12255bff806d5f96e89728df838419f695d3c /fs/xfs/xfs_file.c | |
parent | 67eb7bf836af69b967ab437c6c84e81c4351b957 (diff) | |
download | linux-5bbf5ba693ac6dc323d6608740311c34b978e986.tar.xz |
xfs: reject all unaligned direct writes to reflinked files
commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream.
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>
[slight changes in context due to the new direct I/O code in 4.10+]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 780be7a..1209ad2 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -554,6 +554,15 @@ 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; |