Commit ceda0864 authored by Miao Xie's avatar Miao Xie Committed by Josef Bacik
Browse files

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: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent f42a34b2

fs/btrfs/ctree.h

+20 −2
Original line number Diff line number Diff line
@@ -1362,6 +1362,17 @@ struct btrfs_fs_info { 
	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;
@@ -3687,9 +3698,16 @@ static inline void __btrfs_set_fs_incompat(struct btrfs_fs_info *fs_info, 


	disk_super = fs_info->super_copy;

	features = btrfs_super_incompat_flags(disk_super);

	if (!(features & flag)) {

		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);

	}

}

fs/btrfs/disk-io.c

+5 −0
Original line number Diff line number Diff line
@@ -2086,6 +2086,7 @@ int open_ctree(struct super_block *sb, 
	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 @@ int open_ctree(struct super_block *sb, 
		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) &

fs/btrfs/volumes.c

+1 −9
Original line number Diff line number Diff line
@@ -3674,18 +3674,10 @@ static u32 find_raid56_stripe_len(u32 data_devices, u32 dev_stripe_target) 


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,

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