linux-kernel - Re: [PATCH 1/2] block: fix error code for zone-append

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Date:   Fri, 3 Jul 2020 05:29:50 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Kanchan Joshi <joshi.k@...sung.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "kbusch@...nel.org" <kbusch@...nel.org>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@....de" <hch@....de>, Selvakumar S <selvakuma.s1@...sung.com>,
        Nitesh Shetty <nj.shetty@...sung.com>,
        Javier Gonzalez <javier.gonz@...sung.com>
Subject: Re: [PATCH 1/2] block: fix error code for zone-append

On 2020/07/03 0:42, Kanchan Joshi wrote:
> avoid returning success when it should report failure, preventing
> odd behavior in caller.

You can be more precise here: the odd behavior is an infinite loop in
bio_iov_iter_get_pages() whcih is is the only user of __bio_iov_append_get_pages().

> 
> Signed-off-by: Kanchan Joshi <joshi.k@...sung.com>
> Signed-off-by: Selvakumar S <selvakuma.s1@...sung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@...sung.com>
> Signed-off-by: Javier Gonzalez <javier.gonz@...sung.com>
> ---
>  block/bio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index a7366c0..0cecdbc 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1044,7 +1044,7 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
>  	size_t offset;
>  
>  	if (WARN_ON_ONCE(!max_append_sectors))
> -		return 0;
> +		return -EINVAL;
>  
>  	/*
>  	 * Move page array up in the allocated memory for the bio vecs as far as
> 

Note: the odd behavior mentioned in the commit message cannot currently be
triggered since only zonefs issues REQ_OP_ZONE_APPEND BIOs so we are guaranteed
that max_append_sectors is not 0 in that case. But this fix certainly makes
things more solid. So:

Reviewed-by: Damien Le Moal <damien.lemoal@....com>

-- 
Damien Le Moal
Western Digital Research