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block, bfq-mq: turn BUG_ON on request-size into WARN_ON

BFQ has many checks of internal and external consistency. One of them
checks that an I/O request has still sectors to serve, if it happens
to be retired without being served. If the request has no sector to
serve, a BUG_ON signals the failure and causes the kernel to
terminate. Yet, from a crash report by a user [1], this condition may
happen to hold, in apparently correct functioning, for I/O with a

To address this issue, this commit turns the above BUG_ON into a
WARN_ON. This commit also adds a companion WARN_ON on request
insertion into the scheduler.


Reported-by: Alexandre Frade <>
Signed-off-by: Paolo Valente <>
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Paolo Valente
Paolo Valente committed Nov 14, 2017
1 parent 7352e96 commit 344b0aa219f88341ef60edffa0048eb4efa1d08c
Showing with 3 additions and 1 deletion.
  1. +3 −1 block/bfq-mq-iosched.c
@@ -1540,6 +1540,8 @@ static void bfq_add_request(struct request *rq)
BUG_ON(RQ_BFQQ(rq) != bfqq);
WARN_ON(blk_rq_sectors(rq) == 0);
elv_rb_add(&bfqq->sort_list, rq);
@@ -4962,7 +4964,7 @@ static void bfq_finish_request(struct request *rq)
BUG_ON(blk_rq_sectors(rq) == 0 && !(rq->rq_flags & RQF_STARTED));
WARN_ON(blk_rq_sectors(rq) == 0 && !(rq->rq_flags & RQF_STARTED));
if (likely(rq->rq_flags & RQF_STARTED)) {
unsigned long flags;

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