On 2011-12-21 09:22, Williams, Dan J wrote: > On Wed, Dec 21, 2011 at 12:16 AM, Tao Ma <tm@xxxxxx> wrote: >> On 12/21/2011 03:30 PM, Williams, Dan J wrote: >>> On Tue, Dec 20, 2011 at 10:48 PM, Tao Ma <tm@xxxxxx> wrote: >>>> On 12/21/2011 02:36 PM, Meelis Roos wrote: >>>>>>> - 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. >>>>>> Please also change the comments here since it should never happen in the >>>>>> right workload. >>>>> >>>>> What do you mean by right workload? Normal workload? >>>> yeah, so real_max_depth is the maximum depth we ever have. So in normal >>>> case(shrinking queue depth is also a normal user case), we should never >>>> arrive here. In another word, if tag >= real_max_depth, we should have a >>>> bug in the kernel. >>> >>> So this is what Ed Nadolski suggested, just cut to the chase and do, >>> the following. Seems like the comment is what got us into trouble in >>> the first place. >>> >>> diff --git a/block/blk-tag.c b/block/blk-tag.c >>> index e74d6d1..e297d9d7 100644 >>> --- a/block/blk-tag.c >>> +++ b/block/blk-tag.c >>> @@ -284,16 +284,7 @@ void blk_queue_end_tag(struct request_queue *q, >>> struct request *rq) >>> struct blk_queue_tag *bqt = q->queue_tags; >>> int tag = rq->tag; >>> >>> - 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 == -1 || tag > bqt->real_max_depth); >> I guess tag = bqt->real_max_depth should also be a problem. > > Yes, sorry, should have been >= Can you resend a v2 and I'll get it applied, thanks. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html