linux-kernel - Re: [PATCH v4] block: Fix uninitialized symbol 'bio' in blk_rq_prep

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Message-ID: <f6a50924-e3f8-4175-a97e-4e77ed24b72b@kernel.dk>
Date: Fri, 15 Nov 2024 09:10:07 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Suraj Sonawane <surajsonawane0215@...il.com>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 hch@...radead.org
Subject: Re: [PATCH v4] block: Fix uninitialized symbol 'bio' in
 blk_rq_prep_clone

On 11/15/24 9:07 AM, Suraj Sonawane wrote:
> On 08/10/24 23:22, SurajSonawane2415 wrote:
>> Fix the uninitialized symbol 'bio' in the function blk_rq_prep_clone
>> to resolve the following error:
>> block/blk-mq.c:3199 blk_rq_prep_clone() error: uninitialized symbol 'bio'.
>>
>> Signed-off-by: SurajSonawane2415 <surajsonawane0215@...il.com>
>> ---
>> V1 - Initialize 'bio' to NULL.
>> V2 - Move bio_put(bio) into the bio_ctr error handling block,
>> ensuring memory cleanup occurs only when the bio_ctr fail.
>> V3 - Moved the bio declaration into the loop scope, eliminating
>> the need to set it to NULL at the end of the loop.
>> V4 - Adjusted position of arguments of bio_alloc_clone.
>>
>>   block/blk-mq.c | 13 ++++++-------
>>   1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 4b2c8e940..89c9a6c4d 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -3156,19 +3156,21 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
>>                 int (*bio_ctr)(struct bio *, struct bio *, void *),
>>                 void *data)
>>   {
>> -    struct bio *bio, *bio_src;
>> +    struct bio *bio_src;
>>         if (!bs)
>>           bs = &fs_bio_set;
>>         __rq_for_each_bio(bio_src, rq_src) {
>> -        bio = bio_alloc_clone(rq->q->disk->part0, bio_src, gfp_mask,
>> -                      bs);
>> +        struct bio *bio = bio_alloc_clone(rq->q->disk->part0, bio_src,
>> +                    gfp_mask, bs);
>>           if (!bio)
>>               goto free_and_out;
>>   -        if (bio_ctr && bio_ctr(bio, bio_src, data))
>> +        if (bio_ctr && bio_ctr(bio, bio_src, data)) {
>> +            bio_put(bio);
>>               goto free_and_out;
>> +        }
>>             if (rq->bio) {
>>               rq->biotail->bi_next = bio;
>> @@ -3176,7 +3178,6 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
>>           } else {
>>               rq->bio = rq->biotail = bio;
>>           }
>> -        bio = NULL;
>>       }
>>         /* Copy attributes of the original request to the clone request. */
>> @@ -3196,8 +3197,6 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
>>       return 0;
>>     free_and_out:
>> -    if (bio)
>> -        bio_put(bio);
>>       blk_rq_unprep_clone(rq);
>>         return -ENOMEM;
> 
> Hello Jens!
> 
> I wanted to follow up on this patch I submitted. I have done all the
> suggested changes till v4. I was wondering if you had a chance to
> review it and if there are any comments or feedback.

Sorry missed this one. Is this a legit case of it being used
uninitialized, or is it just cleaning up the code so that smatch is
happy? The commit is woefully non-descriptive, unfortunately. So perhaps
resend this one and improve the commit message.

-- 
Jens Axboe