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

[Bart Van Assche]

On 2/19/19 5:17 PM, Ming Lei wrote:
> On Tue, Feb 19, 2019 at 08:28:19AM -0800, Bart Van Assche wrote:
> > With this patch applied test nvmeof-mp/002 fails as follows:
> >
> > [  694.700400] kernel BUG at lib/sg_pool.c:103!
> > [  694.705932] invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> > [  694.708297] CPU: 2 PID: 349 Comm: kworker/2:1H Tainted: G    B             5.0.0-rc6-dbg+ #2
> > [  694.711730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> > [  694.715113] Workqueue: kblockd blk_mq_run_work_fn
> > [  694.716894] RIP: 0010:sg_alloc_table_chained+0xe5/0xf0
> > [  694.758222] Call Trace:
> > [  694.759645]  nvme_rdma_queue_rq+0x2aa/0xcc0 [nvme_rdma]
> > [  694.764915]  blk_mq_try_issue_directly+0x2a5/0x4b0
> > [  694.771779]  blk_insert_cloned_request+0x11e/0x1c0
> > [  694.778417]  dm_mq_queue_rq+0x3d1/0x770
> > [  694.793400]  blk_mq_dispatch_rq_list+0x5fc/0xb10
> > [  694.798386]  blk_mq_sched_dispatch_requests+0x2f7/0x300
> > [  694.803180]  __blk_mq_run_hw_queue+0xd6/0x180
> > [  694.808933]  blk_mq_run_work_fn+0x27/0x30
> > [  694.810315]  process_one_work+0x4f1/0xa40
> > [  694.813178]  worker_thread+0x67/0x5b0
> > [  694.814487]  kthread+0x1cf/0x1f0
> > [  694.819134]  ret_from_fork+0x24/0x30
> >
> > The code in sg_pool.c that triggers the BUG() statement is as follows:
> >
> > int sg_alloc_table_chained(struct sg_table *table, int nents,
> > 		struct scatterlist *first_chunk)
> > {
> > 	int ret;
> >
> > 	BUG_ON(!nents);
> > [ ... ]
> >
> > Bart.
>
> I can reproduce this issue("kernel BUG at lib/sg_pool.c:103") without mp-bvec patches,
> so looks it isn't the fault of this patchset.

Thanks Ming for your feedback.

Jens, I don't see that issue with kernel v5.0-rc6. Does that mean that 
the sg_pool BUG() is a regression in your for-next branch that predates 
Ming's multi-page bvec patch series?

Thanks,

Bart.