btrfs: track exclusive filesystem operation in flags

There are several operations, usually started from ioctls, that cannot
run concurrently. The status is tracked in
mutually_exclusive_operation_running as an atomic_t. We can easily track
the status as one of the per-filesystem flag bits with same
synchronization guarantees.

The conversion replaces:

* atomic_xchg(..., 1)    ->   test_and_set_bit(FLAG, ...)
* atomic_set(..., 0)     ->   clear_bit(FLAG, ...)

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

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index e653921f05d9..de7b2c897fe0 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -784,8 +784,7 @@ int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
         }
         btrfs_dev_replace_unlock(dev_replace, 1);
 
-        WARN_ON(atomic_xchg(
-                &fs_info->mutually_exclusive_operation_running, 1));
+        WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
         return PTR_ERR_OR_ZERO(task);
 }
@@ -814,7 +813,7 @@ static int btrfs_dev_replace_kthread(void *data)
                         (unsigned int)progress);
         }
         btrfs_dev_replace_continue_on_mount(fs_info);
-        atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+        clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 
         return 0;
 }