- Fix a race that can result in alloc_workspace > cpus.
- Fix to check num_workspace after wakeup.

Signed-off-by: Li Zefan <l...@cn.fujitsu.com>
---
 fs/btrfs/zlib.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index b9cd544..e5b8b22 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -75,16 +75,19 @@ again:
                return workspace;
 
        }
-       spin_unlock(&workspace_lock);
        if (atomic_read(&alloc_workspace) > cpus) {
                DEFINE_WAIT(wait);
+
+               spin_unlock(&workspace_lock);
                prepare_to_wait(&workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
-               if (atomic_read(&alloc_workspace) > cpus)
+               if (atomic_read(&alloc_workspace) > cpus && !num_workspace)
                        schedule();
                finish_wait(&workspace_wait, &wait);
                goto again;
        }
        atomic_inc(&alloc_workspace);
+       spin_unlock(&workspace_lock);
+
        workspace = kzalloc(sizeof(*workspace), GFP_NOFS);
        if (!workspace) {
                ret = -ENOMEM;
-- 
1.7.0.1

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