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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Christoph Hellwig <hch@infradead.org>,
	Hannes Reinecke <hare@suse.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
	Jack Wang <jinpu.wang@cloud.ionos.com>
Subject: [PATCH 4.19 21/24] blk-mq: dont hold q->sysfs_lock in blk_mq_map_swqueue
Date: Thu, 11 Feb 2021 16:02:55 +0100
Message-ID: <20210211150148.681811267@linuxfoundation.org> (raw)
In-Reply-To: <20210211150147.743660073@linuxfoundation.org>

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

commit c6ba933358f0d7a6a042b894dba20cc70396a6d3 upstream.

blk_mq_map_swqueue() is called from blk_mq_init_allocated_queue()
and blk_mq_update_nr_hw_queues(). For the former caller, the kobject
isn't exposed to userspace yet. For the latter caller, hctx sysfs entries
and debugfs are un-registered before updating nr_hw_queues.

On the other hand, commit 2f8f1336a48b ("blk-mq: always free hctx after
request queue is freed") moves freeing hctx into queue's release
handler, so there won't be race with queue release path too.

So don't hold q->sysfs_lock in blk_mq_map_swqueue().

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 block/blk-mq.c |    7 -------
 1 file changed, 7 deletions(-)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2324,11 +2324,6 @@ static void blk_mq_map_swqueue(struct re
 	struct blk_mq_ctx *ctx;
 	struct blk_mq_tag_set *set = q->tag_set;
 
-	/*
-	 * Avoid others reading imcomplete hctx->cpumask through sysfs
-	 */
-	mutex_lock(&q->sysfs_lock);
-
 	queue_for_each_hw_ctx(q, hctx, i) {
 		cpumask_clear(hctx->cpumask);
 		hctx->nr_ctx = 0;
@@ -2362,8 +2357,6 @@ static void blk_mq_map_swqueue(struct re
 		hctx->ctxs[hctx->nr_ctx++] = ctx;
 	}
 
-	mutex_unlock(&q->sysfs_lock);
-
 	queue_for_each_hw_ctx(q, hctx, i) {
 		/*
 		 * If no software queues are mapped to this hardware queue,



  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-11 15:02 [PATCH 4.19 00/24] 4.19.176-rc1 review Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 01/24] tracing/kprobe: Fix to support kretprobe events on unloaded modules Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 02/24] block: fix NULL pointer dereference in register_disk Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 03/24] fgraph: Initialize tracing_graph_pause at task creation Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 04/24] remoteproc: qcom_q6v5_mss: Validate modem blob firmware size before load Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 05/24] remoteproc: qcom_q6v5_mss: Validate MBA " Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 06/24] af_key: relax availability checks for skb size calculation Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 07/24] regulator: core: avoid regulator_resolve_supply() race condition Greg Kroah-Hartman
2021-02-11 15:26   ` Mark Brown
2021-02-11 15:38     ` Greg Kroah-Hartman
2021-02-11 15:40       ` Mark Brown
2021-02-11 18:06         ` Sasha Levin
2021-02-11 15:02 ` [PATCH 4.19 08/24] chtls: Fix potential resource leak Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 09/24] pNFS/NFSv4: Try to return invalid layout in pnfs_layout_process() Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 10/24] iwlwifi: mvm: take mutex for calling iwl_mvm_get_sync_time() Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 11/24] iwlwifi: pcie: add a NULL check in iwl_pcie_txq_unmap Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 12/24] iwlwifi: pcie: fix context info memory leak Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 13/24] iwlwifi: mvm: guard against device removal in reprobe Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 14/24] SUNRPC: Move simple_get_bytes and simple_get_netobj into private header Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 15/24] SUNRPC: Handle 0 length opaque XDR object data properly Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 16/24] lib/string: Add strscpy_pad() function Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 17/24] include/trace/events/writeback.h: fix -Wstringop-truncation warnings Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 18/24] memcg: fix a crash in wb_workfn when a device disappears Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 19/24] Fix unsynchronized access to sev members through svm_register_enc_region Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 20/24] block: dont hold q->sysfs_lock in elevator_init_mq Greg Kroah-Hartman
2021-02-11 15:02 ` Greg Kroah-Hartman [this message]
2021-02-11 15:02 ` [PATCH 4.19 22/24] squashfs: add more sanity checks in id lookup Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 23/24] squashfs: add more sanity checks in inode lookup Greg Kroah-Hartman
2021-02-11 15:02 ` [PATCH 4.19 24/24] squashfs: add more sanity checks in xattr id lookup Greg Kroah-Hartman
2021-02-12  4:46 ` [PATCH 4.19 00/24] 4.19.176-rc1 review Naresh Kamboju
2021-02-12  7:42   ` Greg Kroah-Hartman
2021-02-12 10:29     ` Naresh Kamboju
2021-02-12 11:00       ` Greg Kroah-Hartman
2021-02-12 16:18 ` Shuah Khan

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