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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Ming Lei <ming.lei@redhat.com>, Keith Busch <kbusch@kernel.org>,
	Christoph Hellwig <hch@lst.de>,
	John Garry <john.garry@huawei.com>, Jens Axboe <axboe@kernel.dk>,
	Sasha Levin <sashal@kernel.org>,
	linux-block@vger.kernel.org
Subject: [PATCH AUTOSEL 5.13 17/26] blk-mq: don't grab rq's refcount in blk_mq_check_expired()
Date: Mon, 23 Aug 2021 20:53:47 -0400	[thread overview]
Message-ID: <20210824005356.630888-17-sashal@kernel.org> (raw)
In-Reply-To: <20210824005356.630888-1-sashal@kernel.org>

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit c797b40ccc340b8a66f7a7842aecc90bf749f087 ]

Inside blk_mq_queue_tag_busy_iter() we already grabbed request's
refcount before calling ->fn(), so needn't to grab it one more time
in blk_mq_check_expired().

Meantime remove extra request expire check in blk_mq_check_expired().

Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210811155202.629575-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-mq.c | 30 +++++-------------------------
 1 file changed, 5 insertions(+), 25 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c732aa581124..6dfa572ac1fc 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -923,34 +923,14 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 	unsigned long *next = priv;
 
 	/*
-	 * Just do a quick check if it is expired before locking the request in
-	 * so we're not unnecessarilly synchronizing across CPUs.
-	 */
-	if (!blk_mq_req_expired(rq, next))
-		return true;
-
-	/*
-	 * We have reason to believe the request may be expired. Take a
-	 * reference on the request to lock this request lifetime into its
-	 * currently allocated context to prevent it from being reallocated in
-	 * the event the completion by-passes this timeout handler.
-	 *
-	 * If the reference was already released, then the driver beat the
-	 * timeout handler to posting a natural completion.
-	 */
-	if (!refcount_inc_not_zero(&rq->ref))
-		return true;
-
-	/*
-	 * The request is now locked and cannot be reallocated underneath the
-	 * timeout handler's processing. Re-verify this exact request is truly
-	 * expired; if it is not expired, then the request was completed and
-	 * reallocated as a new request.
+	 * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
+	 * be reallocated underneath the timeout handler's processing, then
+	 * the expire check is reliable. If the request is not expired, then
+	 * it was completed and reallocated as a new request after returning
+	 * from blk_mq_check_expired().
 	 */
 	if (blk_mq_req_expired(rq, next))
 		blk_mq_rq_timed_out(rq, reserved);
-
-	blk_mq_put_rq_ref(rq);
 	return true;
 }
 
-- 
2.30.2


  parent reply	other threads:[~2021-08-24  0:55 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24  0:53 [PATCH AUTOSEL 5.13 01/26] iwlwifi: pnvm: accept multiple HW-type TLVs Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 02/26] iwlwifi: add new SoF with JF devices Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 03/26] iwlwifi: add new so-jf devices Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 04/26] opp: remove WARN when no valid OPPs remain Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 05/26] cpufreq: blocklist Qualcomm sm8150 in cpufreq-dt-platdev Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 06/26] virtio: Improve vq->broken access to avoid any compiler optimization Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 07/26] virtio_pci: Support surprise removal of virtio pci device Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 08/26] virtio_vdpa: reject invalid vq indices Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 09/26] vringh: Use wiov->used to check for read/write desc order Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 10/26] tools/virtio: fix build Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 11/26] platform/x86: asus-nb-wmi: Allow configuring SW_TABLET_MODE method with a module option Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 12/26] platform/x86: asus-nb-wmi: Add tablet_mode_sw=lid-flip quirk for the TP200s Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 13/26] qed: qed ll2 race condition fixes Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 14/26] qed: Fix null-pointer dereference in qed_rdma_create_qp() Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 15/26] Revert "drm/amd/pm: fix workload mismatch on vega10" Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 16/26] drm/amd/pm: change the workload type for some cards Sasha Levin
2021-08-24  0:53 ` Sasha Levin [this message]
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 18/26] drm: Copy drm_wait_vblank to user before returning Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 19/26] platform/x86: gigabyte-wmi: add support for X570 GAMING X Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 20/26] drm/nouveau: recognise GA107 Sasha Levin
2021-08-24 17:08   ` Lyude Paul
2021-08-30 12:17     ` Sasha Levin
2021-08-30 17:08       ` Lyude Paul
2021-08-30 17:09         ` Lyude Paul
2021-08-30 21:55           ` Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 21/26] drm/nouveau/disp: power down unused DP links during init Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 22/26] drm/nouveau/kms/nv50: workaround EFI GOP window channel format differences Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 23/26] drm/nouveau: block a bunch of classes from userspace Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 24/26] platform/x86: gigabyte-wmi: add support for B450M S2H V2 Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 25/26] net/rds: dma_map_sg is entitled to merge entries Sasha Levin
2021-08-24  0:53 ` [PATCH AUTOSEL 5.13 26/26] arm64: initialize all of CNTHCTL_EL2 Sasha Levin

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