Subject: Re: [PATCH -next] radi10: fix leak of 'r10bio->remaining' for
 recovery
To:     Paul Menzel <pmenzel@molgen.mpg.de>,
        Yu Kuai <yukuai1@huaweicloud.com>
Cc:     song@kernel.org, neilb@suse.de, linux-raid@vger.kernel.org,
        linux-kernel@vger.kernel.org, yi.zhang@huawei.com,
        yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20230307022739.2656920-1-yukuai1@huaweicloud.com>
 <7684548b-5e6b-975b-67c2-98c686a4925f@molgen.mpg.de>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <d4ef4c18-c377-2568-17e6-dea344b7f479@huaweicloud.com>
Date:   Tue, 7 Mar 2023 18:42:51 +0800
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Hi,

在 2023/03/07 17:53, Paul Menzel 写道:
> Dear Yu,
> 
> 
> Thank you for your patch.
> 
> Am 07.03.23 um 03:27 schrieb Yu Kuai:
>> From: Yu Kuai <yukuai3@huawei.com>
> 
> There is a small typo in the prefix of the commit message summary: raid10.
> 
> It also seems common to use md/raid10 as prefix.
> 
>> raid10_sync_request() will add 'r10bio->remaining' for both rdev and
>> replacement rdev. However, if the read io failed,
> 
> fails (present tense for problem description/summary)
> 
>> recovery_request_write() will return without issuring the write io, in
> 
> 1.  return*s*
> 2.  assuring?
> 
>> this case, end_sync_request() is only called once and 'remaining' is
>> leaked, which will cause io hang.
> 
> leaked, causing an io hang.
> 
>> Fix the probleming by decreasing 'remaining' according to if 'bio' and
> 
> problem
> 

Thanks for those advices, I'll send a new version after code changes is
reviewed.

Thanks,
Kuai

>> 'repl_bio' is valid.
>>
>> Fixes: 24afd80d99f8 ("md/raid10: handle recovery of replacement 
>> devices.")
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>>   drivers/md/raid10.c | 23 +++++++++++++----------
>>   1 file changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>> index a8b5fecef136..f7002a1aa9cf 100644
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -2611,11 +2611,22 @@ static void recovery_request_write(struct 
>> mddev *mddev, struct r10bio *r10_bio)
>>   {
>>       struct r10conf *conf = mddev->private;
>>       int d;
>> -    struct bio *wbio, *wbio2;
>> +    struct bio *wbio = r10_bio->devs[1].bio;
>> +    struct bio *wbio2 = r10_bio->devs[1].repl_bio;
>> +
>> +    /* Need to test wbio2->bi_end_io before we call
>> +     * submit_bio_noacct as if the former is NULL,
>> +     * the latter is free to free wbio2.
>> +     */
>> +    if (wbio2 && !wbio2->bi_end_io)
>> +        wbio2 = NULL;
>>       if (!test_bit(R10BIO_Uptodate, &r10_bio->state)) {
>>           fix_recovery_read_error(r10_bio);
>> -        end_sync_request(r10_bio);
>> +        if (wbio->bi_end_io)
>> +            end_sync_request(r10_bio);
>> +        if (wbio2)
>> +            end_sync_request(r10_bio);
>>           return;
>>       }
>> @@ -2624,14 +2635,6 @@ static void recovery_request_write(struct mddev 
>> *mddev, struct r10bio *r10_bio)
>>        * and submit the write request
>>        */
>>       d = r10_bio->devs[1].devnum;
>> -    wbio = r10_bio->devs[1].bio;
>> -    wbio2 = r10_bio->devs[1].repl_bio;
>> -    /* Need to test wbio2->bi_end_io before we call
>> -     * submit_bio_noacct as if the former is NULL,
>> -     * the latter is free to free wbio2.
>> -     */
>> -    if (wbio2 && !wbio2->bi_end_io)
>> -        wbio2 = NULL;
>>       if (wbio->bi_end_io) {
>>           atomic_inc(&conf->mirrors[d].rdev->nr_pending);
>>           md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
> 
> 
> Kind regards,
> 
> Paul
> 
> .
>