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Subject[PATCH] block: fix blk_queue_end_tag()
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Date
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.

Cc: Tao Ma <boyu.mt@taobao.com>
Reported-by: Meelis Roos <mroos@ut.ee>
Reported-by: Ed Nadolski <edmund.nadolski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Functionally the same as Tao Ma's fix [1], but just moves the warn into the
if() directly.

[1]: http://marc.info/?l=linux-scsi&m=132439698602441&w=2

--
Dan

block/blk-tag.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/blk-tag.c b/block/blk-tag.c
index e74d6d1..6e61262 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -286,12 +286,13 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq)

BUG_ON(tag == -1);

- if (unlikely(tag >= bqt->max_depth)) {
+ if (WARN_ONCE(tag >= bqt->real_max_depth,
+ "%s: tag %d greater than tag map size: %d\n",
+ __func__, tag, bqt->real_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;
}



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