Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 26 Oct 2016 15:51:01 -0700 | Subject | Re: bio linked list corruption. |
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On Wed, Oct 26, 2016 at 3:40 PM, Dave Jones <davej@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
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