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btrfs: comment the rest of implicit barriers before waitqueue_active

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There are atomic operations that imply the barrier for waitqueue_active
mixed in an if-condition.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2015-02-16 19:41:40 +01:00
parent 779adf0f64
commit ee86395458
5 changed files with 22 additions and 0 deletions
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4
fs/btrfs/delayed-inode.c
View File

@ -463,6 +463,10 @@ static int __btrfs_add_delayed_deletion_item(struct btrfs_delayed_node *node,
static void finish_one_item(struct btrfs_delayed_root *delayed_root)
{
int seq = atomic_inc_return(&delayed_root->items_seq);
/*
* atomic_dec_return implies a barrier for waitqueue_active
*/
if ((atomic_dec_return(&delayed_root->items) <
BTRFS_DELAYED_BACKGROUND || seq % BTRFS_DELAYED_BATCH == 0) &&
waitqueue_active(&delayed_root->wait))

3
fs/btrfs/disk-io.c
View File

@ -802,6 +802,9 @@ static void run_one_async_done(struct btrfs_work *work)
limit = btrfs_async_submit_limit(fs_info);
limit = limit * 2 / 3;
/*
* atomic_dec_return implies a barrier for waitqueue_active
*/
if (atomic_dec_return(&fs_info->nr_async_submits) < limit &&
waitqueue_active(&fs_info->async_submit_wait))
wake_up(&fs_info->async_submit_wait);

3
fs/btrfs/inode.c
View File

@ -1096,6 +1096,9 @@ static noinline void async_cow_submit(struct btrfs_work *work)
nr_pages = (async_cow->end - async_cow->start + PAGE_CACHE_SIZE) >>
PAGE_CACHE_SHIFT;
/*
* atomic_sub_return implies a barrier for waitqueue_active
*/
if (atomic_sub_return(nr_pages, &root->fs_info->async_delalloc_pages) <
5 * 1024 * 1024 &&
waitqueue_active(&root->fs_info->async_submit_wait))

9
fs/btrfs/locking.c
View File

@ -79,6 +79,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
write_lock(&eb->lock);
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_inc(&eb->spinning_writers);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_writers) &&
waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);
@ -86,6 +89,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
BUG_ON(atomic_read(&eb->blocking_readers) == 0);
read_lock(&eb->lock);
atomic_inc(&eb->spinning_readers);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
@ -229,6 +235,9 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->blocking_readers) == 0);
/*
* atomic_dec_and_test implies a barrier for waitqueue_active
*/
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);

3
fs/btrfs/volumes.c
View File

@ -345,6 +345,9 @@ loop_lock:
pending = pending->bi_next;
cur->bi_next = NULL;
/*
* atomic_dec_return implies a barrier for waitqueue_active
*/
if (atomic_dec_return(&fs_info->nr_async_bios) < limit &&
waitqueue_active(&fs_info->async_submit_wait))
wake_up(&fs_info->async_submit_wait);