Re: WARNING: CPU: 2 PID: 207 at drivers/nvme/host/core.c:527 nvme_setup_cmd+0x3d3
From: jianchao.wang <hidden>
Date: 2018-02-01 03:03:01
Also in:
linux-nvme
Hi Jens On 01/31/2018 11:29 PM, Jens Axboe wrote:
quoted hunk ↗ jump to hunk
How about something like the below?diff --git a/block/blk-merge.c b/block/blk-merge.c index 8452fc7164cc..cee102fb060e 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c@@ -574,8 +574,13 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, blk_rq_get_max_sectors(req, blk_rq_pos(req))) return 0; + /* + * For DISCARDs, the segment count isn't interesting since + * the requests have no data attached. + */ total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; - if (blk_phys_contig_segment(q, req->biotail, next->bio)) { + if (total_phys_segments && + blk_phys_contig_segment(q, req->biotail, next->bio)) { if (req->nr_phys_segments == 1) req->bio->bi_seg_front_size = seg_size; if (next->nr_phys_segments == 1)
This patch will avoid the nr_phys_segments to be set to 0xffff,
but the merged req will have two bios but zero nr_phys_segments.
We have to align with the DISCARD merging strategy.
Please refer to:
/*
* Number of discard segments (or ranges) the driver needs to fill in.
* Each discard bio merged into a request is counted as one segment.
*/
static inline unsigned short blk_rq_nr_discard_segments(struct request *rq)
{
return max_t(unsigned short, rq->nr_phys_segments, 1);
}
bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
struct bio *bio)
{
unsigned short segments = blk_rq_nr_discard_segments(req);
if (segments >= queue_max_discard_segments(q))
goto no_merge;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
goto no_merge;
req->biotail->bi_next = bio;
req->biotail = bio;
req->__data_len += bio->bi_iter.bi_size;
req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
req->nr_phys_segments = segments + 1;
blk_account_io_start(req, false);
return true;
no_merge:
req_set_nomerge(q, req);
return false;
}
blk_rq_nr_discard_segments will get a wrong value finally.
Maybe we could change blk_rq_nr_discard_segments to iterate and count the bios in one request
to decide the DISCARD request nr_phy_segment. And discard the nr_phys_segments operations in
the DISCARD merging path, plus your patch here.
Thanks
Jianchao
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