Re: [PATCH] inode: always initialize mapping->wb_err

[Lu Fengqi <lufq.fnst@cn.fujitsu.com>]

On Sat, May 26, 2018 at 07:42:46AM -0400, Jeff Layton wrote:
>On Sat, 2018-05-26 at 10:42 +0800, Lu Fengqi wrote:
>> Creating a file reuses the inode object by kmem_cache_alloc without
>> initializing maping->wb_err. If it contains an unseen writeback error,
>> fsync will report an error on the file, even if no error has ever occurred
>> after the file was created.
>> 
>> Before commit b4678df184b3 ("errseq: Always report a writeback error
>> once"), any errors that occur before the file descriptor is opened will be
>> ignored, causing the issue not to be found. Afterward, any unseen writeback
>> error will be reported once, including, of course, the uninitialized
>> maping->wb_err, which exposes this problem.
>> 
>> Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
>> ---
>>  fs/inode.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/fs/inode.c b/fs/inode.c
>> index 13ceb98c3bd3..bf02dc9d1837 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -182,6 +182,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
>>  	mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
>>  	mapping->private_data = NULL;
>>  	mapping->writeback_index = 0;
>> +	mapping->wb_err = 0;
>>  	inode->i_private = NULL;
>>  	inode->i_mapping = mapping;
>>  	INIT_HLIST_HEAD(&inode->i_dentry);	/* buggered by rcu freeing */
>
>(cc'ing Darrick)
>
>I think Darrick had a similar patch that also fixed up some related
>inode reuse issues in xfs. Darrick, were you planning to get that
>merged for v4.17?

Oh, I missed Darrick's patch. Thanks for your reminder.

-- 
Thanks,
Lu

>-- 
>Jeff Layton <jlayton@kernel.org>
>
>