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btrfs: add barrier for waitqueue_active in clear_btree_io_tree

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waitqueue_active should be preceded by a barrier, in this function we
don't need to call it all the time.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2015-10-10 18:24:48 +02:00
parent 730d9ec36b
commit b666a9cd99
1 changed files with 6 additions and 0 deletions
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6
fs/btrfs/transaction.c
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@ -82,6 +82,12 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
static void clear_btree_io_tree(struct extent_io_tree *tree)
{
spin_lock(&tree->lock);
/*
* Do a single barrier for the waitqueue_active check here, the state
* of the waitqueue should not change once clear_btree_io_tree is
* called.
*/
smp_mb();
while (!RB_EMPTY_ROOT(&tree->state)) {
struct rb_node *node;
struct extent_state *state;