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From:   Martijn Coenen <maco@android.com>
To:     axboe@kernel.dk, hch@lst.de
Cc:     bvanassche@acm.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@android.com,
        Martijn Coenen <maco@android.com>
Subject: [PATCH] loop: Only change blocksize when needed.
Date:   Tue, 10 Mar 2020 14:12:30 +0100
Message-Id: <20200310131230.106427-1-maco@android.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Return early in loop_set_block_size() if the requested block size is
identical to the one we already have; this avoids expensive calls to
freeze the block queue.

Signed-off-by: Martijn Coenen <maco@android.com>
---
 drivers/block/loop.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c1c844ad6b1a..a42c49e04954 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1541,16 +1541,16 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 	if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
 		return -EINVAL;
 
-	if (lo->lo_queue->limits.logical_block_size != arg) {
-		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
-	}
+	if (lo->lo_queue->limits.logical_block_size == arg)
+		return 0;
+
+	sync_blockdev(lo->lo_device);
+	kill_bdev(lo->lo_device);
 
 	blk_mq_freeze_queue(lo->lo_queue);
 
 	/* kill_bdev should have truncated all the pages */
-	if (lo->lo_queue->limits.logical_block_size != arg &&
-			lo->lo_device->bd_inode->i_mapping->nrpages) {
+	if (lo->lo_device->bd_inode->i_mapping->nrpages) {
 		err = -EAGAIN;
 		pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
 			__func__, lo->lo_number, lo->lo_file_name,
-- 
2.25.1.481.gfbce0eb801-goog