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

[Jeff Layton <jlayton@kernel.org>]

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