Commit 22cd2e7d authored Aug 09, 2012 by Arne Jansen Committed by Chris Mason Aug 28, 2012

Btrfs: fix race in run_clustered_refs



With commit

commit d1270cd9
Author: Arne Jansen <sensille@gmx.net>
Date:   Tue Sep 13 15:16:43 2011 +0200

     Btrfs: put back delayed refs that are too new

I added a window where the delayed_ref's head->ref_mod code can diverge
from the sum of the remaining refs, because we release the head->mutex
in the middle. This leads to btrfs_lookup_extent_info returning wrong
numbers. This patch fixes this by adjusting the head's ref_mod with each
delayed ref we run.

Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

parent b12a3b1e

fs/btrfs/extent-tree.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -2318,6 +2318,23 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
		ref->in_tree = 0;
		rb_erase(&ref->rb_node, &delayed_refs->root);
		delayed_refs->num_entries--;
		if (locked_ref) {
		/*
		* when we play the delayed ref, also correct the
		* ref_mod on head
		*/
		switch (ref->action) {
		case BTRFS_ADD_DELAYED_REF:
		case BTRFS_ADD_DELAYED_EXTENT:
		locked_ref->node.ref_mod -= ref->ref_mod;
		break;
		case BTRFS_DROP_DELAYED_REF:
		locked_ref->node.ref_mod += ref->ref_mod;
		break;
		default:
		WARN_ON(1);
		}
		}
		spin_unlock(&delayed_refs->lock);

		ret = run_one_delayed_ref(trans, root, ref, extent_op,

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