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@xxxxxx>
---
fs/xfs/xfs_iomap.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 5d06a2d..c3cc175 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -955,6 +955,7 @@ 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;
@@ -964,7 +965,7 @@ 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)
@@ -975,7 +976,7 @@ 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;
}
@@ -995,7 +996,8 @@ 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)
@@ -1006,7 +1008,7 @@ 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);
}
--
2.1.4
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