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OpenCloudOS-Kernel
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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>
This commit is contained in:
Christoph Hellwig 2016-09-19 11:26:39 +10:00 committed by Dave Chinner
parent 17879e8f86
commit 66642c5c1d
1 changed files with 6 additions and 4 deletions
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10
fs/xfs/xfs_iomap.c
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@ -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);
}