Commit 11ef160f authored Sep 23, 2009 by Chris Mason

Btrfs: fix releasepage to avoid unlocking extents we haven't locked



During releasepage, we try to drop any extent_state structs for the
bye offsets of the page we're releaseing.  But the code was incorrectly
telling clear_extent_bit to delete the state struct unconditionallly.

Normally this would be fine because we have the page locked, but other
parts of btrfs will lock down an entire extent, the most common place
being IO completion.

releasepage was deleting the extent state without first locking the extent,
which may result in removing a state struct that another process had
locked down.  The fix here is to leave the NODATASUM and EXTENT_LOCKED
bits alone in releasepage.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

parent 46562cec

fs/btrfs/extent_io.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -2809,8 +2809,13 @@ int try_release_extent_state(struct extent_map_tree *map,
		else {
		if ((mask & GFP_NOFS) == GFP_NOFS)
		mask = GFP_NOFS;
		clear_extent_bit(tree, start, end, EXTENT_UPTODATE,
		1, 1, NULL, mask);
		/*
		* at this point we can safely clear everything except the
		* locked bit and the nodatasum bit
		*/
		clear_extent_bit(tree, start, end,
		~(EXTENT_LOCKED \| EXTENT_NODATASUM),
		0, 0, NULL, mask);
		}
		return ret;
		}

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