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authorChristoph Hellwig <hch@lst.de>2016-09-19 11:26:39 +1000
committerDave Chinner <david@fromorbit.com>2016-09-19 11:26:39 +1000
commit66642c5c1dea411dd2842159f9f297ce8e914994 (patch)
tree693c729488f40154f7fd6878afc9897209ec82cd /fs/xfs/xfs_iomap.c
parent17879e8f865f4ed8b6f9041a2687ad40f13ae460 (diff)
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xfs: take the ilock shared if possible in xfs_file_iomap_begin
We always just read the extent first, and will later lock exlusively after first dropping the lock in case we actually allocate blocks. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_iomap.c')
-rw-r--r--fs/xfs/xfs_iomap.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index ac677d032e3a..fe4a26d752d0 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -954,6 +954,7 @@ xfs_file_iomap_begin(
struct xfs_bmbt_irec imap;
xfs_fileoff_t offset_fsb, end_fsb;
int nimaps = 1, error = 0;
+ unsigned lockmode;
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
@@ -963,7 +964,7 @@ xfs_file_iomap_begin(
iomap);
}
- xfs_ilock(ip, XFS_ILOCK_EXCL);
+ lockmode = xfs_ilock_data_map_shared(ip);
ASSERT(offset <= mp->m_super->s_maxbytes);
if ((xfs_fsize_t)offset + length > mp->m_super->s_maxbytes)
@@ -974,7 +975,7 @@ xfs_file_iomap_begin(
error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
&nimaps, XFS_BMAPI_ENTIRE);
if (error) {
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
return error;
}
@@ -994,7 +995,8 @@ xfs_file_iomap_begin(
* xfs_iomap_write_direct() expects the shared lock. It
* is unlocked on return.
*/
- xfs_ilock_demote(ip, XFS_ILOCK_EXCL);
+ if (lockmode == XFS_ILOCK_EXCL)
+ xfs_ilock_demote(ip, lockmode);
error = xfs_iomap_write_direct(ip, offset, length, &imap,
nimaps);
if (error)
@@ -1005,7 +1007,7 @@ xfs_file_iomap_begin(
} else {
ASSERT(nimaps);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ xfs_iunlock(ip, lockmode);
trace_xfs_iomap_found(ip, offset, length, 0, &imap);
}