linux-kernel - Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing crash shortly after bootup

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Date:   Mon, 22 Feb 2021 20:22:09 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
Cc:     David Anderson <dvander@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Alistair Delva <adelva@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Amit Pundir <amit.pundir@...aro.org>,
        YongQin Liu <yongqin.liu@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing
 crash shortly after bootup

On Mon, Feb 22, 2021 at 7:39 PM Chaitanya Kulkarni
<Chaitanya.Kulkarni@....com> wrote:
>
> On 2/22/21 19:07, John Stultz wrote:
> > [   34.784901] ueventd: LoadWithAliases was unable to load platform:regulatory
> > [   34.785313]  bio_alloc_bioset+0x14/0x230
> > [   34.796189]  bio_clone_fast+0x28/0x80
> > [   34.799848]  bio_split+0x50/0xd0
> > [   34.803072]  blk_crypto_fallback_encrypt_bio+0x2ec/0x5e8
> > [   34.808384]  blk_crypto_fallback_bio_prep+0xfc/0x140
> > [   34.813345]  __blk_crypto_bio_prep+0x13c/0x150
> > [   34.817784]  submit_bio_noacct+0x3c0/0x548
> > [   34.821880]  submit_bio+0x48/0x200
> > [   34.825278]  ext4_io_submit+0x50/0x68
> > [   34.828939]  ext4_writepages+0x558/0xca8
> > [   34.832860]  do_writepages+0x58/0x108
> > [   34.836522]  __writeback_single_inode+0x44/0x510
> > [   34.841137]  writeback_sb_inodes+0x1e0/0x4a8
> > [   34.845404]  __writeback_inodes_wb+0x78/0xe8
> > [   34.849670]  wb_writeback+0x274/0x3e8
> > [   34.853328]  wb_workfn+0x308/0x5f0
> > [   34.856726]  process_one_work+0x1ec/0x4d0
> > [   34.860734]  worker_thread+0x44/0x478
> > [   34.864392]  kthread+0x140/0x150
> > [   34.867618]  ret_from_fork+0x10/0x30
> > [   34.871197] Code: a9ba7bfd 910003fd f9000bf3 7900bfa1 (f9403441)
> > [   34.877289] ---[ end trace e6c2a3ab108278f0 ]---
> > [   34.893636] Kernel panic - not syncing: Oops: Fatal exception
> >
>
> If you have time then until you get the reply from others, can you try
> following patch ?
>
> diff --git a/block/bio.c b/block/bio.c
> index a1c4d2900c7a..9976400ec66a 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -663,7 +663,10 @@ struct bio *bio_clone_fast(struct bio *bio, gfp_t
> gfp_mask, struct bio_set *bs)
>  {
>         struct bio *b;
>
> -       b = bio_alloc_bioset(gfp_mask, 0, bs);
> +       if (bs)
> +               b = bio_alloc_bioset(gfp_mask, 0, bs);
> +       else
> +               b = bio_kmalloc(gfp_mask, 0);
>         if (!b)
>                 return NULL;
>
> P.S.This is purely based on the code inspection and it may not solve your
> issue. Proceed with the caution as it may *break* your system.

So with an initial quick test, this patch (along with the follow-on
one you sent) seems to avoid the issue.

I'm wondering if given there are multiple call sites, that in
bio_alloc_bioset() would something like the following make more sense?
(apologies, copy pasted so this is whitespace corrupted)
thanks
-john

diff --git a/block/bio.c b/block/bio.c
index a1c4d2900c7a..391d5cde79fc 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -402,6 +402,9 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask,
unsigned short nr_iovecs,
        struct bio *bio;
        void *p;

+       if(!bs)
+               return bio_kmalloc(gfp_mask, 0);
+
        /* should not use nobvec bioset for nr_iovecs > 0 */
        if (WARN_ON_ONCE(!mempool_initialized(&bs->bvec_pool) && nr_iovecs > 0))
                return NULL;