Commit f2b20d43 authored Dec 29, 2011 by Dan Williams Committed by Jens Axboe Dec 29, 2011

block: fix blk_queue_end_tag()

Commit 5e081591 "block: warn if tag is greater than real_max_depth"
cleaned up blk_queue_end_tag() to warn when the tag is truly invalid
(greater than real_max_depth).  However, it changed behavior in the tag <
max_depth case to not end the request.  Leading to triggering of
BUG_ON(blk_queued_rq(rq)) in the request completion path:

  http://marc.info/?l=linux-kernel&m=132204370518629&w=2



In order to allow blk_queue_resize_tags() to shrink the tag space
blk_queue_end_tag() must always complete tags with a value less than
real_max_depth regardless of the current max_depth.  The comment about
"handling the shrink case" seems to be what prompted changes in this
space, so remove it and BUG on all invalid tags (made even simpler by
Matthew's suggestion to use an unsigned compare).

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Tao Ma <boyu.mt@taobao.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Reported-by: Meelis Roos <mroos@ut.ee>
Reported-by: Ed Nadolski <edmund.nadolski@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 609f6ea1

block/blk-tag.c

+2 −11

Original line number	Diff line number	Diff line
		@@ -282,18 +282,9 @@ EXPORT_SYMBOL(blk_queue_resize_tags);
		void blk_queue_end_tag(struct request_queue q, struct request rq)
		{
		struct blk_queue_tag *bqt = q->queue_tags;
		int tag = rq->tag;
		unsigned tag = rq->tag; /* negative tags invalid */

		BUG_ON(tag == -1);

		if (unlikely(tag >= bqt->max_depth)) {
		/*
		* This can happen after tag depth has been reduced.
		* But tag shouldn't be larger than real_max_depth.
		*/
		WARN_ON(tag >= bqt->real_max_depth);
		return;
		}
		BUG_ON(tag >= bqt->real_max_depth);

		list_del_init(&rq->queuelist);
		rq->cmd_flags &= ~REQ_QUEUED;

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