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Commit 66642c5c authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Dave Chinner
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent 17879e8f

fs/xfs/xfs_iomap.c

+6 −4
Original line number Diff line number Diff line
@@ -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);

	}