tree 5c5df70a252ea14da6063d2c6c3de4a4e769ecae
parent 609f6ea1c9cdfe0c43a927e13205a57d0c266d5a
author Dan Williams <dan.j.williams@intel.com> 1325146588 +0100
committer Jens Axboe <axboe@kernel.dk> 1325146588 +0100

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>