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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>
This commit is contained in:
Miao Xie 2013-04-11 10:30:16 +00:00 committed by Josef Bacik
parent f42a34b2f1
commit ceda086424
3 changed files with 26 additions and 11 deletions
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22
fs/btrfs/ctree.h
View File

@ -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;
@ -3688,8 +3699,15 @@ 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)) {
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);
}
}

5
fs/btrfs/disk-io.c
View File

@ -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) &

10
fs/btrfs/volumes.c
View File

@ -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,