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

Bart Van Assche
2019-02-19T16:28:25Z

On Sun, 2019-02-17 at 21:11 +0800, Ming Lei wrote:
> The following patch should fix this issue:
>
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index bed065904677..066b66430523 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -363,13 +363,15 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
> struct bio_vec bv, bvprv = { NULL };
> int prev = 0;
> unsigned int seg_size, nr_phys_segs;
> - unsigned front_seg_size = bio->bi_seg_front_size;
> + unsigned front_seg_size;
> struct bio *fbio, *bbio;
> struct bvec_iter iter;
>
> if (!bio)
> return 0;
>
> + front_seg_size = bio->bi_seg_front_size;
> +
> switch (bio_op(bio)) {
> case REQ_OP_DISCARD:
> case REQ_OP_SECURE_ERASE:

Hi Ming,

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.