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Btrfs: fix race in run_clustered_refs

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commit d1270cd91f
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>
This commit is contained in:
Arne Jansen 2012-08-09 00:16:53 -06:00 committed by Chris Mason
parent b12a3b1ea2
commit 22cd2e7de7
1 changed files with 17 additions and 0 deletions
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17
fs/btrfs/extent-tree.c
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@ -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,