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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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fs/btrfs/inode.c
+1 -3
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@@ -1007,9 +1007,7 @@ 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(nr_pages, &root->fs_info->async_delalloc_pages);
if (atomic_read(&root->fs_info->async_delalloc_pages) <
if (atomic_sub_return(nr_pages, &root->fs_info->async_delalloc_pages) <
5 * 1024 * 1024 &&
waitqueue_active(&root->fs_info->async_submit_wait))
wake_up(&root->fs_info->async_submit_wait);