Re: [dm-devel] [PATCH V15 00/18] block: support multi-page bvec

Bart Van Assche
2019-02-15T17:14:15Z

On Fri, 2019-02-15 at 08:49 -0700, Jens Axboe wrote:
> On 2/15/19 4:13 AM, Ming Lei wrote:
> > This patchset brings multi-page bvec into block layer:
>
> Applied, thanks Ming. Let's hope it sticks!

Hi Jens and Ming,

Test nvmeof-mp/002 fails with Jens' for-next branch from this morning.
I have not yet tried to figure out which patch introduced the failure.
Anyway, this is what I see in the kernel log for test nvmeof-mp/002:

[ 475.611363] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[ 475.621188] #PF error: [normal kernel read fault]
[ 475.623148] PGD 0 P4D 0
[ 475.624737] Oops: 0000 [#1] PREEMPT SMP KASAN
[ 475.626628] CPU: 1 PID: 277 Comm: kworker/1:1H Tainted: G B 5.0.0-rc6-dbg+ #1
[ 475.630232] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 475.633855] Workqueue: kblockd blk_mq_requeue_work
[ 475.635777] RIP: 0010:__blk_recalc_rq_segments+0xbe/0x590
[ 475.670948] Call Trace:
[ 475.693515] blk_recalc_rq_segments+0x2f/0x50
[ 475.695081] blk_insert_cloned_request+0xbb/0x1c0
[ 475.701142] dm_mq_queue_rq+0x3d1/0x770
[ 475.707225] blk_mq_dispatch_rq_list+0x5fc/0xb10
[ 475.717137] blk_mq_sched_dispatch_requests+0x256/0x300
[ 475.721767] __blk_mq_run_hw_queue+0xd6/0x180
[ 475.725920] __blk_mq_delay_run_hw_queue+0x25c/0x290
[ 475.727480] blk_mq_run_hw_queue+0x119/0x1b0
[ 475.732019] blk_mq_run_hw_queues+0x7b/0xa0
[ 475.733468] blk_mq_requeue_work+0x2cb/0x300
[ 475.736473] process_one_work+0x4f1/0xa40
[ 475.739424] worker_thread+0x67/0x5b0
[ 475.741751] kthread+0x1cf/0x1f0
[ 475.746034] ret_from_fork+0x24/0x30

(gdb) list *(__blk_recalc_rq_segments+0xbe)
0xffffffff816a152e is in __blk_recalc_rq_segments (block/blk-merge.c:366).
361 struct bio *bio)
362 {
363 struct bio_vec bv, bvprv = { NULL };
364 int prev = 0;
365 unsigned int seg_size, nr_phys_segs;
366 unsigned front_seg_size = bio->bi_seg_front_size;
367 struct bio *fbio, *bbio;
368 struct bvec_iter iter;
369
370 if (!bio)

Bart.