From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Ming Lei <ming.lei@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Hannes Reinecke <hare@suse.com>,
Greg KH <gregkh@linuxfoundation.org>,
Mike Snitzer <snitzer@redhat.com>,
Bart Van Assche <bvanassche@acm.org>
Subject: [PATCH V3 3/5] blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue
Date: Mon, 26 Aug 2019 10:51:44 +0800 [thread overview]
Message-ID: <20190826025146.31158-4-ming.lei@redhat.com> (raw)
In-Reply-To: <20190826025146.31158-1-ming.lei@redhat.com>
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>
---
block/blk-mq.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6968de9d7402..b0ee0cac737f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2456,11 +2456,6 @@ static void blk_mq_map_swqueue(struct request_queue *q)
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;
@@ -2521,8 +2516,6 @@ static void blk_mq_map_swqueue(struct request_queue *q)
HCTX_TYPE_DEFAULT, i);
}
- mutex_unlock(&q->sysfs_lock);
-
queue_for_each_hw_ctx(q, hctx, i) {
/*
* If no software queues are mapped to this hardware queue,
--
2.20.1
next prev parent reply other threads:[~2019-08-26 2:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 2:51 [PATCH V3 0/5] block: don't acquire .sysfs_lock before removing mq & iosched kobjects Ming Lei
2019-08-26 2:51 ` [PATCH V3 1/5] block: Remove blk_mq_register_dev() Ming Lei
2019-08-26 2:51 ` [PATCH V3 2/5] block: don't hold q->sysfs_lock in elevator_init_mq Ming Lei
2019-08-26 2:51 ` Ming Lei [this message]
2019-08-26 2:51 ` [PATCH V3 4/5] block: add helper for checking if queue is registered Ming Lei
2019-08-26 2:51 ` [PATCH V3 5/5] block: split .sysfs_lock into two locks Ming Lei
2019-08-26 16:24 ` Bart Van Assche
2019-08-27 10:37 ` Ming Lei
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