Commit 1e190f8e authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
Browse files

xfs: improve the IOMAP_NOWAIT check for COW inodes 



Only bail out once we know that a COW allocation is actually required,
similar to how we handle normal data fork allocations.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 5c5b6f75

fs/xfs/xfs_iomap.c

+5 −18
Original line number Diff line number Diff line
@@ -693,15 +693,8 @@ xfs_ilock_for_iomap( 
	 * COW writes may allocate delalloc space or convert unwritten COW

	 * extents, so we need to make sure to take the lock exclusively here.

	 */

	if (xfs_is_cow_inode(ip) && is_write) {

		/*

		 * FIXME: It could still overwrite on unshared extents and not

		 * need allocation.

		 */

		if (flags & IOMAP_NOWAIT)

			return -EAGAIN;

	if (xfs_is_cow_inode(ip) && is_write)

		mode = XFS_ILOCK_EXCL;

	}



	/*

	 * Extents not yet cached requires exclusive access, don't block.  This
@@ -769,12 +762,6 @@ xfs_direct_write_iomap_begin( 
	if (offset + length > i_size_read(inode))

		iomap_flags |= IOMAP_F_DIRTY;



	/*

	 * Lock the inode in the manner required for the specified operation and

	 * check for as many conditions that would result in blocking as

	 * possible. This removes most of the non-blocking checks from the

	 * mapping code below.

	 */

	error = xfs_ilock_for_iomap(ip, flags, &lockmode);

	if (error)

		return error;
@@ -784,11 +771,11 @@ xfs_direct_write_iomap_begin( 
	if (error)

		goto out_unlock;



	/*

	 * Break shared extents if necessary. Checks for non-blocking IO have

	 * been done up front, so we don't need to do them here.

	 */

	if (imap_needs_cow(ip, flags, &imap, nimaps)) {

		error = -EAGAIN;

		if (flags & IOMAP_NOWAIT)

			goto out_unlock;



		/* may drop and re-acquire the ilock */

		error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,

				&lockmode, flags & IOMAP_DIRECT);