Re: [next-20260108]kernel BUG at drivers/scsi/scsi_lib.c:1173!

[Ming Lei <ming.lei@redhat.com>]

On Fri, Jan 09, 2026 at 07:26:01PM +0530, Venkat Rao Bagalkote wrote:
> 
> On 09/01/26 6:28 pm, Ming Lei wrote:
> > On Fri, Jan 09, 2026 at 05:51:15PM +0530, Venkat Rao Bagalkote wrote:
> > > On 09/01/26 5:25 pm, Ming Lei wrote:
> > > > On Fri, Jan 09, 2026 at 05:14:36PM +0530, Venkat Rao Bagalkote wrote:
> > > > > On 09/01/26 12:19 pm, Ming Lei wrote:
> > > > > > On Thu, Jan 08, 2026 at 09:56:39PM -0800, Christoph Hellwig wrote:
> > > > > > > I've seen the same when running xfstests on xfs, and bisected it to:
> > > > > > > 
> > > > > > > commit ee623c892aa59003fca173de0041abc2ccc2c72d
> > > > > > > Author: Ming Lei <ming.lei@redhat.com>
> > > > > > > Date:   Wed Dec 31 11:00:55 2025 +0800
> > > > > > > 
> > > > > > >        block: use bvec iterator helper for bio_may_need_split()
> > > > > > > 
> > > > > > Hi Christoph and Venkat Rao Bagalkote,
> > > > > > 
> > > > > > Unfortunately I can't duplicate the issue in my environment, can you test
> > > > > > the following patch?
> > > > > > 
> > > > > > diff --git a/block/blk.h b/block/blk.h
> > > > > > index 98f4dfd4ec75..980eef1f5690 100644
> > > > > > --- a/block/blk.h
> > > > > > +++ b/block/blk.h
> > > > > > @@ -380,7 +380,7 @@ static inline bool bio_may_need_split(struct bio *bio,
> > > > > >                    return true;
> > > > > >            bv = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
> > > > > > -       if (bio->bi_iter.bi_size > bv->bv_len)
> > > > > > +       if (bio->bi_iter.bi_size > bv->bv_len - bio->bi_iter.bi_bvec_done)
> > > > > >                    return true;
> > > > > >            return bv->bv_len + bv->bv_offset > lim->max_fast_segment_size;
> > > > > >     }
> > > > > Hello Ming,
> > > > > 
> > > > > 
> > > > > This is not helping. I am hitting this issue, during kernel build itself.
> > > > Can you confirm if it can fix the blktests ext4/056 first?
> > > > 
> > > > If kernel building is running over new patched kernel, please provide the
> > > > dmesg log. And if it is reproduciable, can you confirm if it can be fixed
> > > > by reverting ee623c892aa59003 (block: use bvec iterator helper for bio_may_need_split())?
> > > 
> > > Unfortunately, even with revert, build fails.
> > > 
> > > 
> > > 
> > > commit c64b2ee9cddcb31546c8622ef018d344544a9388 (HEAD)
> > > Author: Super User <root@ltc-zzci-1.ltc.tadn.ibm.com>
> > > Date:   Fri Jan 9 06:51:19 2026 -0600
> > > 
> > >      Revert "block: use bvec iterator helper for bio_may_need_split()"
> > > 
> > >      This reverts commit ee623c892aa59003fca173de0041abc2ccc2c72d.
> > OK, then your issue isn't related with the above change.
> > 
> > Can you reproduce & collect dmesg log with the bad sg/rq/bio/bvec info by
> > applying the attached debug patch?
> > 
> > Also if possible, please collect your scsi queue's limit info before
> > reproducing the issue:
> > 
> > 	(cd /sys/block/$SD/queue && find . -type f -exec grep -aH . {} \;)
> 
> Hello Ming,
> 
> After applying the patch shared via attachment also, I see build failure.
> 
> I have attached the kernel config file.
> 
> 
> git diff
> diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
> index 752060d7261c..33c1b6a0a738 100644
> --- a/block/blk-mq-dma.c
> +++ b/block/blk-mq-dma.c
> @@ -4,8 +4,75 @@
>   */
>  #include <linux/blk-integrity.h>
>  #include <linux/blk-mq-dma.h>
> +#include <linux/scatterlist.h>
>  #include "blk.h"

Hi Venkat,

Thanks for your test.

But you didn't apply the whole debug patch in the following link:

https://lore.kernel.org/linux-block/aWD7j3NR_m6EyZv1@fedora/

otherwise something like "=== __blk_rq_map_sg DEBUG DUMP ===" will be
dumped in dmesg log.

> 
> make -j 48 -s && make modules_install && make install
> [ 5625.770436] ------------[ cut here ]------------
> [ 5625.770476] WARNING: block/blk-mq-dma.c:309 at

If the whole debug patch is applied correctly, the above line number should
have become 378 instead of original 309.

Please re-apply the debug patch & reproduce again.


Thanks, 
Ming