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/ctree.h b/fs/btrfs/ctree.h
index 1a85040..c3b15f8 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1362,6 +1362,17 @@
wait_queue_head_t transaction_blocked_wait;
wait_queue_head_t async_submit_wait;
+ /*
+ * Used to protect the incompat_flags, compat_flags, compat_ro_flags
+ * when they are updated.
+ *
+ * Because we do not clear the flags for ever, so we needn't use
+ * the lock on the read side.
+ *
+ * We also needn't use the lock when we mount the fs, because
+ * there is no other task which will update the flag.
+ */
+ spinlock_t super_lock;
struct btrfs_super_block *super_copy;
struct btrfs_super_block *super_for_commit;
struct block_device *__bdev;
@@ -3688,8 +3699,15 @@
disk_super = fs_info->super_copy;
features = btrfs_super_incompat_flags(disk_super);
if (!(features & flag)) {
- features |= flag;
- btrfs_set_super_incompat_flags(disk_super, features);
+ spin_lock(&fs_info->super_lock);
+ features = btrfs_super_incompat_flags(disk_super);
+ if (!(features & flag)) {
+ features |= flag;
+ btrfs_set_super_incompat_flags(disk_super, features);
+ printk(KERN_INFO "btrfs: setting %llu feature flag\n",
+ flag);
+ }
+ spin_unlock(&fs_info->super_lock);
}
}
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) &
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5aa52ee..76ded9e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3674,18 +3674,10 @@
static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type)
{
- u64 features;
-
if (!(type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6)))
return;
- features = btrfs_super_incompat_flags(info->super_copy);
- if (features & BTRFS_FEATURE_INCOMPAT_RAID56)
- return;
-
- features |= BTRFS_FEATURE_INCOMPAT_RAID56;
- btrfs_set_super_incompat_flags(info->super_copy, features);
- printk(KERN_INFO "btrfs: setting RAID5/6 feature flag\n");
+ btrfs_set_fs_incompat(info, RAID56);
}
static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
