From 0a6219a95f0b0690fb7094acb26002e7a4791197 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 16 Nov 2016 18:07:05 +0800 Subject: [PATCH] block: deal with stale req count of plug list In both legacy and mq path, req count of plug list is computed before allocating request, so the number can be stale when falling back to slept allocation, also the new introduced wbt can sleep too. This patch deals with the case by checking if plug list becomes empty, and fixes the KASAN report of 'BUG: KASAN: stack-out-of-bounds' which is introduced by Shaohua's patches of dispatching big request. Fixes: 600271d900002(blk-mq: immediately dispatch big size request) Fixes: 50d24c34403c6(block: immediately dispatch big size request) Cc: Shaohua Li Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-core.c | 5 ++++- block/blk-mq.c | 7 +++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/block/blk-core.c b/block/blk-core.c index eea246567884..473dd698effd 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1753,8 +1753,11 @@ get_rq: /* * If this is the first request added after a plug, fire * of a plug trace. + * + * @request_count may become stale because of schedule + * out, so check plug list again. */ - if (!request_count) + if (!request_count || list_empty(&plug->list)) trace_block_plug(q); else { struct request *last = list_entry_rq(plug->list.prev); diff --git a/block/blk-mq.c b/block/blk-mq.c index ae8df5ec20d3..f39e69c732cc 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1497,6 +1497,13 @@ static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio) struct request *last = NULL; blk_mq_bio_to_request(rq, bio); + + /* + * @request_count may become stale because of schedule + * out, so check the list again. + */ + if (list_empty(&plug->mq_list)) + request_count = 0; if (!request_count) trace_block_plug(q); else -- 2.30.2