diff options
| author | Christoph Hellwig <hch@lst.de> | 2017-02-07 00:00:54 +0300 |
|---|---|---|
| committer | Darrick J. Wong <darrick.wong@oracle.com> | 2017-02-07 04:47:46 +0300 |
| commit | 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e (patch) | |
| tree | 47f55c2f61169e2774cd73770c2237ff9356a5ec | |
| parent | 4dd2eb633598cb6a5a0be2fd9a2be0819f5eeb5f (diff) | |
| download | linux-54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e.tar.xz | |
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>
| -rw-r--r-- | fs/xfs/xfs_file.c | 9 | ||||
| -rw-r--r-- | fs/xfs/xfs_iomap.c | 12 | ||||
| -rw-r--r-- | fs/xfs/xfs_trace.h | 2 |
3 files changed, 11 insertions, 12 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; diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 84fb8788431b..52d9d1f61d4a 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1026,17 +1026,7 @@ xfs_file_iomap_begin( if (error) goto out_unlock; - /* - * We're here because we're trying to do a directio write to a - * region that isn't aligned to a filesystem block. If the - * extent is shared, fall back to buffered mode to handle the - * RMW. - */ - if (!(flags & IOMAP_REPORT) && shared) { - trace_xfs_reflink_bounce_dio_write(ip, &imap); - error = -EREMCHG; - goto out_unlock; - } + ASSERT((flags & IOMAP_REPORT) || !shared); } if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) { diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h index 9e9bb9538bb6..b654893130e2 100644 --- a/fs/xfs/xfs_trace.h +++ b/fs/xfs/xfs_trace.h @@ -3249,7 +3249,7 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_convert_cow); DEFINE_RW_EVENT(xfs_reflink_reserve_cow); DEFINE_RW_EVENT(xfs_reflink_allocate_cow_range); -DEFINE_INODE_IREC_EVENT(xfs_reflink_bounce_dio_write); +DEFINE_SIMPLE_IO_EVENT(xfs_reflink_bounce_dio_write); DEFINE_IOMAP_EVENT(xfs_reflink_find_cow_mapping); DEFINE_INODE_IREC_EVENT(xfs_reflink_trim_irec); |