btrfs: use mutex in btrfs_resume_balance_async

While the spinlock does not cause problems, using the mutex is more
correct and consistent with others. The global status of balance is eg.
checked from btrfs_pause_balance or btrfs_cancel_balance with mutex.

Resuming balance happens during mount or ro->rw remount. In the former
case, no other user of the balance_ctl exists, in the latter, balance
cannot run until the ro/rw transition is finished.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 197b91b..447a0c2 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3959,12 +3959,12 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
 {
        struct task_struct *tsk;
 
-       spin_lock(&fs_info->balance_lock);
+       mutex_lock(&fs_info->balance_mutex);
        if (!fs_info->balance_ctl) {
-               spin_unlock(&fs_info->balance_lock);
+               mutex_unlock(&fs_info->balance_mutex);
                return 0;
        }
-       spin_unlock(&fs_info->balance_lock);
+       mutex_unlock(&fs_info->balance_mutex);
 
        if (btrfs_test_opt(fs_info, SKIP_BALANCE)) {
                btrfs_info(fs_info, "force skipping balance");