On Wed, Oct 26, 2016 at 3:40 PM, Dave Jones <da...@codemonkey.org.uk> wrote: > > I gave it a shot too for shits & giggles. > This falls out during boot. > > [ 9.278420] WARNING: CPU: 0 PID: 1 at block/blk-mq.c:1181 > blk_sq_make_request+0x465/0x4a0
Hmm. That's the WARN_ON_ONCE(rq->mq_ctx != ctx); that I added to blk_mq_merge_queue_io(), and I really think that warning is valid, and the fact that it triggers shows that something is wrong with locking. We just did a spin_lock(&ctx->lock); and that lock is *supposed* to protect the __blk_mq_insert_request(), but that uses rq->mq_ctx. So if rq->mq_ctx != ctx, then we're locking the wrong context. Jens - please explain to me why I'm wrong. Or maybe I actually might have found the problem? In which case please send me a patch that fixes it ;) Dave: it might be a good idea to split that "WARN_ON_ONCE()" in blk_mq_merge_queue_io() into two, since right now it can trigger both for the blk_mq_bio_to_request(rq, bio); path _and_ for the if (!blk_mq_attempt_merge(q, ctx, bio)) { blk_mq_bio_to_request(rq, bio); goto insert_rq; path. If you split it into two: one before that "insert_rq:" label, and one before the "goto insert_rq" thing, then we could see if it is just one of the blk_mq_merge_queue_io() cases (or both) that is broken.. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html