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Btrfs: use a lock to protect incompat/compat flag of the super block

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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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5
fs/btrfs/disk-io.c
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@@ -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) &