Btrfs: use a lock to protect incompat/compat flag of the super block
The following case will make the incompat/compat flag of the super block
be recovered.
Task1 |Task2
flags = btrfs_super_incompat_flags(); |
|flags = btrfs_super_incompat_flags();
flags |= new_flag1; |
|flags |= new_flag2;
btrfs_set_super_incompat_flags(flags); |
|btrfs_set_super_incompat_flags(flags);
the new_flag1 is recovered.
In order to avoid this problem, we introduce a lock named super_lock into
the btrfs_fs_info structure. If we want to update incompat/compat flags
of the super block, we must hold it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9f83e5b..8a7a366 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2086,6 +2086,7 @@
spin_lock_init(&fs_info->defrag_inodes_lock);
spin_lock_init(&fs_info->free_chunk_lock);
spin_lock_init(&fs_info->tree_mod_seq_lock);
+ spin_lock_init(&fs_info->super_lock);
rwlock_init(&fs_info->tree_mod_log_lock);
mutex_init(&fs_info->reloc_mutex);
seqlock_init(&fs_info->profiles_lock);
@@ -2349,6 +2350,10 @@
goto fail_alloc;
}
+ /*
+ * Needn't use the lock because there is no other task which will
+ * update the flag.
+ */
btrfs_set_super_incompat_flags(disk_super, features);
features = btrfs_super_compat_ro_flags(disk_super) &
