Re: [PATCH] iomap: Make sure iomap_end is called after iomap_begin

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Jun 15, 2020 at 06:02:44PM +0200, Andreas Gruenbacher wrote:
> Make sure iomap_end is always called when iomap_begin succeeds: the
> filesystem may take locks in iomap_begin and release them in iomap_end,
> for example.
> 
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> ---
>  fs/iomap/apply.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> index 76925b40b5fd..c00a14d825db 100644
> --- a/fs/iomap/apply.c
> +++ b/fs/iomap/apply.c
> @@ -46,10 +46,10 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
>  	ret = ops->iomap_begin(inode, pos, length, flags, &iomap, &srcmap);
>  	if (ret)
>  		return ret;
> -	if (WARN_ON(iomap.offset > pos))
> -		return -EIO;
> -	if (WARN_ON(iomap.length == 0))
> -		return -EIO;
> +	if (WARN_ON(iomap.offset > pos) || WARN_ON(iomap.length == 0)) {

<urk> Forgot to actually review the original patch. :P

Why combine these WARN_ON?  Before, you could distinguish between your
iomap_begin method returning zero length vs. bad offset.

--D

> +		written = -EIO;
> +		goto out;
> +	}
>  
>  	trace_iomap_apply_dstmap(inode, &iomap);
>  	if (srcmap.type != IOMAP_HOLE)
> @@ -80,6 +80,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
>  	written = actor(inode, pos, length, data, &iomap,
>  			srcmap.type != IOMAP_HOLE ? &srcmap : &iomap);
>  
> +out:
>  	/*
>  	 * Now the data has been copied, commit the range we've copied.  This
>  	 * should not fail unless the filesystem has had a fatal error.
> 
> base-commit: 97e0204907ac4c42c6e94ef466a047523f34b853
> -- 
> 2.26.2
>