Commit 1f1397b7 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Dave Chinner
Browse files

xfs: don't allocate into the data fork for an unshare request 



For an unshare request, we only have to take action if the data fork has
a shared mapping.  We don't care if someone else set up a cow operation.
If we find nothing in the data fork, return a hole to avoid allocating
space.

Note that fallocate will replace the delalloc reservation with an
unwritten extent anyway, so this has no user-visible effects outside of
avoiding unnecessary updates.

Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent 397b2d7e

fs/xfs/xfs_iomap.c

+3 −2
Original line number Diff line number Diff line
@@ -1006,8 +1006,9 @@ xfs_buffered_write_iomap_begin( 
	if (eof)

		imap.br_startoff = end_fsb; /* fake hole until the end */



	/* We never need to allocate blocks for zeroing a hole. */

	if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) {

	/* We never need to allocate blocks for zeroing or unsharing a hole. */

	if ((flags & (IOMAP_UNSHARE | IOMAP_ZERO)) &&

	    imap.br_startoff > offset_fsb) {

		xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);

		goto out_unlock;

	}