Re: WARNING: CPU: 2 PID: 207 at drivers/nvme/host/core.c:527 nvme_setup_cmd+0x3d3
From: Keith Busch <hidden>
Date: 2018-02-01 18:12:09
Also in:
linux-nvme
On Thu, Feb 01, 2018 at 10:58:23AM -0700, Jens Axboe wrote:
I was able to reproduce on a test box, pretty trivially in fact: # echo mq-deadline > /sys/block/nvme2n1/queue/scheduler # mkfs.ext4 /dev/nvme2n1 # mount /dev/nvme2n1 /data -o discard # dd if=/dev/zero of=/data/10g bs=1M count=10k # sync # rm /data/10g # sync <- triggered
Nice! Thanks, this recipe works for me too.
Your patch still doesn't work, but mainly because we init the segments to 0 when setting up a discard. The below works for me, and cleans up the merge path a bit, since your patch was missing various adjustments on both the merged and freed request.
Yep, your update is very similiar to my real patch, but I'm missing one thing (elv_merge_requests). If you're already testing successfully with your patch, I don't mind if you want to move forward with yours.
quoted hunk ↗ jump to hunk
diff --git a/block/blk-core.c b/block/blk-core.c index a2005a485335..e4561c95fc23 100644 --- a/block/blk-core.c +++ b/block/blk-core.c@@ -3282,6 +3282,8 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq, { if (bio_has_data(bio)) rq->nr_phys_segments = bio_phys_segments(q, bio); + else if (bio_op(bio) == REQ_OP_DISCARD) + rq->nr_phys_segments = 1; rq->__data_len = bio->bi_iter.bi_size; rq->bio = rq->biotail = bio;diff --git a/block/blk-merge.c b/block/blk-merge.c index 8452fc7164cc..782940c65d8a 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c@@ -550,6 +550,24 @@ static bool req_no_special_merge(struct request *req) return !q->mq_ops && req->special; } +static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, + struct request *next) +{ + 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(next->bio) > + blk_rq_get_max_sectors(req, blk_rq_pos(req))) + goto no_merge; + + req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); + return true; +no_merge: + req_set_nomerge(q, req); + return false; +} + static int ll_merge_requests_fn(struct request_queue *q, struct request *req, struct request *next) {@@ -683,9 +701,13 @@ static struct request *attempt_merge(struct request_queue *q, * If we are allowed to merge, then append bio list * from next to rq and release next. merge_requests_fn * will have updated segment counts, update sector - * counts here. + * counts here. Handle DISCARDs separately, as they + * have separate settings. */ - if (!ll_merge_requests_fn(q, req, next)) + if (req_op(req) == REQ_OP_DISCARD) { + if (!req_attempt_discard_merge(q, req, next)) + return NULL; + } else if (!ll_merge_requests_fn(q, req, next)) return NULL; /*@@ -715,7 +737,8 @@ static struct request *attempt_merge(struct request_queue *q, req->__data_len += blk_rq_bytes(next); - elv_merge_requests(q, req, next); + if (req_op(req) != REQ_OP_DISCARD) + elv_merge_requests(q, req, next); /* * 'next' is going away, so update stats accordingly-- Jens Axboe