This is a note to let you know that I've just added the patch titled
block: mq-deadline: Fix dd_finish_request() for zoned devices
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-mq-deadline-fix-dd_finish_request-for-zoned-devices.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2820e5d0820ac4daedff1272616a53d9c7682fd2 Mon Sep 17 00:00:00 2001
From: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Date: Thu, 24 Nov 2022 11:12:07 +0900
Subject: block: mq-deadline: Fix dd_finish_request() for zoned devices
From: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
commit 2820e5d0820ac4daedff1272616a53d9c7682fd2 upstream.
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@xxxxxxxxxxxxxxx>
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Link: https://lore.kernel.org/r/20221124021208.242541-2-damien.lemoal@xxxxxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/mq-deadline.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -791,6 +791,18 @@ static void dd_prepare_request(struct re
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().
*
@@ -813,7 +825,6 @@ static void dd_finish_request(struct req
struct deadline_data *dd = q->elevator->elevator_data;
const u8 ioprio_class = dd_rq_ioclass(rq);
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
- struct dd_per_prio *per_prio = &dd->per_prio[prio];
/*
* The block layer core may call dd_finish_request() without having
@@ -829,9 +840,10 @@ static void dd_finish_request(struct req
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);
}
}
Patches currently in stable-queue which might be from damien.lemoal@xxxxxxxxxxxxxxxxxx are
queue-5.15/ata-ahci-fix-pcs-quirk-application-for-suspend.patch
queue-5.15/block-mq-deadline-do-not-break-sequential-write-streams-to-zoned-hdds.patch
queue-5.15/block-mq-deadline-fix-dd_finish_request-for-zoned-devices.patch
