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authorDamien Le Moal <damien.lemoal@opensource.wdc.com>2022-11-24 05:12:07 +0300
committerJens Axboe <axboe@kernel.dk>2022-11-24 16:29:36 +0300
commit2820e5d0820ac4daedff1272616a53d9c7682fd2 (patch)
tree6f24d044342b01926d30faa1fb6e282a9db6c1ce /block/mq-deadline.c
parent85168d416e5d3184b77dbec8fee75c9439894afa (diff)
downloadlinux-2820e5d0820ac4daedff1272616a53d9c7682fd2.tar.xz
block: mq-deadline: Fix dd_finish_request() for zoned devices
dd_finish_request() tests if the per prio fifo_list is not empty to determine if request dispatching must be restarted for handling blocked write requests to zoned devices with a call to blk_mq_sched_mark_restart_hctx(). While simple, this implementation has 2 problems: 1) Only the priority level of the completed request is considered. However, writes to a zone may be blocked due to other writes to the same zone using a different priority level. While this is unlikely to happen in practice, as writing a zone with different IO priorirites does not make sense, nothing in the code prevents this from happening. 2) The use of list_empty() is dangerous as dd_finish_request() does not take dd->lock and may run concurrently with the insert and dispatch code. Fix these 2 problems by testing the write fifo list of all priority levels using the new helper dd_has_write_work(), and by testing each fifo list using list_empty_careful(). Fixes: c807ab520fc3 ("block/mq-deadline: Add I/O priority support") Cc: <stable@vger.kernel.org> Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Link: https://lore.kernel.org/r/20221124021208.242541-2-damien.lemoal@opensource.wdc.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/mq-deadline.c')
-rw-r--r--block/mq-deadline.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 5639921dfa92..36374481cb87 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -789,6 +789,18 @@ static void dd_prepare_request(struct request *rq)
rq->elv.priv[0] = NULL;
}
+static bool dd_has_write_work(struct blk_mq_hw_ctx *hctx)
+{
+ struct deadline_data *dd = hctx->queue->elevator->elevator_data;
+ enum dd_prio p;
+
+ for (p = 0; p <= DD_PRIO_MAX; p++)
+ if (!list_empty_careful(&dd->per_prio[p].fifo_list[DD_WRITE]))
+ return true;
+
+ return false;
+}
+
/*
* Callback from inside blk_mq_free_request().
*
@@ -828,9 +840,10 @@ static void dd_finish_request(struct request *rq)
spin_lock_irqsave(&dd->zone_lock, flags);
blk_req_zone_write_unlock(rq);
- if (!list_empty(&per_prio->fifo_list[DD_WRITE]))
- blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
spin_unlock_irqrestore(&dd->zone_lock, flags);
+
+ if (dd_has_write_work(rq->mq_hctx))
+ blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
}
}