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Btrfs: barrier before waitqueue_active

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We need a barrir before calling waitqueue_active otherwise we will miss
wakeups.  So in places that do atomic_dec(); then atomic_read() use
atomic_dec_return() which imply a memory barrier (see memory-barriers.txt)
and then add an explicit memory barrier everywhere else that need them.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Josef Bacik
2012-08-01 15:36:24 -04:00
committed by Chris Mason
parent 1fa11e265f
commit 66657b318e
5 changed files with 10 additions and 12 deletions
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7
fs/btrfs/delayed-inode.c
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@@ -512,8 +512,8 @@ static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
rb_erase(&delayed_item->rb_node, root);
delayed_item->delayed_node->count--;
atomic_dec(&delayed_root->items);
if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND &&
if (atomic_dec_return(&delayed_root->items) <
BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);
}
@@ -1056,8 +1056,7 @@ static void btrfs_release_delayed_inode(struct btrfs_delayed_node *delayed_node)
delayed_node->count--;
delayed_root = delayed_node->root->fs_info->delayed_root;
atomic_dec(&delayed_root->items);
if (atomic_read(&delayed_root->items) <
if (atomic_dec_return(&delayed_root->items) <
BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);