Btrfs: disallow mutually exclusive admin operations from user mode

Btrfs admin operations that are manually started from user mode
and that cannot be executed at the same time return -EINPROGRESS.
A common way to enter and leave this locked section is introduced
since it used to be specific to the balance operation.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d2c0bccca607..33ca36b37a6a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2952,6 +2952,7 @@ static int balance_kthread(void *data)
                 ret = btrfs_balance(fs_info->balance_ctl, NULL);
         }
 
+        atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
         mutex_unlock(&fs_info->balance_mutex);
         mutex_unlock(&fs_info->volume_mutex);
 
@@ -2974,6 +2975,7 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
                 return 0;
         }
 
+        WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
         tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
         if (IS_ERR(tsk))
                 return PTR_ERR(tsk);