linux-kernel - [PATCH] loop: Only freeze block queue when needed.

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Message-Id: <20200310130654.92205-1-maco@android.com>
Date:   Tue, 10 Mar 2020 14:06:54 +0100
From:   Martijn Coenen <maco@...roid.com>
To:     axboe@...nel.dk, hch@....de
Cc:     bvanassche@....org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Martijn Coenen <maco@...roid.com>
Subject: [PATCH] loop: Only freeze block queue when needed.

__loop_update_dio() can be called as a part of loop_set_fd(), when the
block queue is not yet up and running; avoid freezing the block queue in
that case, since that is an expensive operation.

Signed-off-by: Martijn Coenen <maco@...roid.com>
---
 drivers/block/loop.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 739b372a5112..c1c844ad6b1a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -214,7 +214,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
 	 * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup
 	 * will get updated by ioctl(LOOP_GET_STATUS)
 	 */
-	blk_mq_freeze_queue(lo->lo_queue);
+	if (lo->lo_state == Lo_bound)
+		blk_mq_freeze_queue(lo->lo_queue);
 	lo->use_dio = use_dio;
 	if (use_dio) {
 		blk_queue_flag_clear(QUEUE_FLAG_NOMERGES, lo->lo_queue);
@@ -223,7 +224,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
 		blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_queue);
 		lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
 	}
-	blk_mq_unfreeze_queue(lo->lo_queue);
+	if (lo->lo_state == Lo_bound)
+		blk_mq_unfreeze_queue(lo->lo_queue);
 }
 
 static int
-- 
2.25.1.481.gfbce0eb801-goog