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

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Message-ID: <20200703062055.GA26058@test-zns>
Date:   Fri, 3 Jul 2020 11:50:55 +0530
From:   Kanchan Joshi <joshi.k@...sung.com>
To:     Damien Le Moal <Damien.LeMoal@....com>
Cc:     "axboe@...nel.dk" <axboe@...nel.dk>,
        "kbusch@...nel.org" <kbusch@...nel.org>,
        "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 Fri, Jul 03, 2020 at 05:29:50AM +0000, Damien Le Moal wrote:
>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().
Sure. Kept that in cover letter, but missed here.
>>
>> 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:
Yes, zonefs will not run into this. Future users of zone-append may. I
encountered this endless loop while testing user zone-append path.
>Reviewed-by: Damien Le Moal <damien.lemoal@....com>
>
>-- 
>Damien Le Moal
>Western Digital Research
>