Re: [PATCH] Btrfs: fix an oops of log replay

[Liu Bo <liubo2009@cn.fujitsu.com>]

On 08/31/2011 04:17 PM, Arne Jansen wrote:
> On 06.08.2011 10:35, Liu Bo wrote:
>> When btrfs recovers from a crash, it may hit the oops below:
>>
>> ------------[ cut here ]------------
>> kernel BUG at fs/btrfs/inode.c:4580!
>> [...]
>> RIP: 0010:[<ffffffffa03df251>]  [<ffffffffa03df251>] btrfs_add_link+0x161/0x1c0 [btrfs]
>> [...]
>> Call Trace:
>>  [<ffffffffa03e7b31>] ? btrfs_inode_ref_index+0x31/0x80 [btrfs]
>>  [<ffffffffa04054e9>] add_inode_ref+0x319/0x3f0 [btrfs]
>>  [<ffffffffa0407087>] replay_one_buffer+0x2c7/0x390 [btrfs]
>>  [<ffffffffa040444a>] walk_down_log_tree+0x32a/0x480 [btrfs]
>>  [<ffffffffa0404695>] walk_log_tree+0xf5/0x240 [btrfs]
>>  [<ffffffffa0406cc0>] btrfs_recover_log_trees+0x250/0x350 [btrfs]
>>  [<ffffffffa0406dc0>] ? btrfs_recover_log_trees+0x350/0x350 [btrfs]
>>  [<ffffffffa03d18b2>] open_ctree+0x1442/0x17d0 [btrfs]
>> [...]
>>
>> This comes from that while replaying an inode ref item, we forget to
>> check those old conflicting DIR_ITEM and DIR_INDEX items in fs/file tree,
>> then we will come to conflict corners which lead to BUG_ON().
> 
> Is this a workaround for an on-disk corruption or a bug fix for the
> log replay code? It sounds like the latter, but I ask to be sure :)
> 

The latter one, for log replay when we recover from a btrfs crash.

thanks,
liubo

> -Arne
> 
>> Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
>> ---
>>  fs/btrfs/tree-log.c |   28 ++++++++++++++++++++++++----
>>  1 files changed, 24 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
>> index babee65..786639f 100644
>> --- a/fs/btrfs/tree-log.c
>> +++ b/fs/btrfs/tree-log.c
>> @@ -799,14 +799,15 @@ static noinline int add_inode_ref(struct btrfs_trans_handle *trans,
>>  				  struct extent_buffer *eb, int slot,
>>  				  struct btrfs_key *key)
>>  {
>> -	struct inode *dir;
>> -	int ret;
>>  	struct btrfs_inode_ref *ref;
>> +	struct btrfs_dir_item *di;
>> +	struct inode *dir;
>>  	struct inode *inode;
>> -	char *name;
>> -	int namelen;
>>  	unsigned long ref_ptr;
>>  	unsigned long ref_end;
>> +	char *name;
>> +	int namelen;
>> +	int ret;
>>  	int search_done = 0;
>>  
>>  	/*
>> @@ -909,6 +910,25 @@ again:
>>  	}
>>  	btrfs_release_path(path);
>>  
>> +	/* look for a conflicting sequence number */
>> +	di = btrfs_lookup_dir_index_item(trans, root, path, btrfs_ino(dir),
>> +					 btrfs_inode_ref_index(eb, ref),
>> +					 name, namelen, 0);
>> +	if (di && !IS_ERR(di)) {
>> +		ret = drop_one_dir_item(trans, root, path, dir, di);
>> +		BUG_ON(ret);
>> +	}
>> +	btrfs_release_path(path);
>> +
>> +	/* look for a conflicing name */
>> +	di = btrfs_lookup_dir_item(trans, root, path, btrfs_ino(dir),
>> +				   name, namelen, 0);
>> +	if (di && !IS_ERR(di)) {
>> +		ret = drop_one_dir_item(trans, root, path, dir, di);
>> +		BUG_ON(ret);
>> +	}
>> +	btrfs_release_path(path);
>> +
>>  insert:
>>  	/* insert our name */
>>  	ret = btrfs_add_link(trans, dir, inode, name, namelen, 0,
> 
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