linux-kernel - [PATCH 5.18 087/879] loop: implement ->free

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Message-Id: <20220607165005.218796914@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 18:53:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 087/879] loop: implement ->free_disk

From: Christoph Hellwig <hch@....de>

[ Upstream commit d2c7f56f8b5256d57f9e3fc7794c31361d43bdd9 ]

Ensure that the lo_device which is stored in the gendisk private
data is valid until the gendisk is freed.  Currently the loop driver
uses a lot of effort to make sure a device is not freed when it is
still in use, but to to fix a potential deadlock this will be relaxed
a bit soon.

Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jan Kara <jack@...e.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/loop.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a58595f5ee2c..ed7bec11948c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1768,6 +1768,14 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
 	mutex_unlock(&lo->lo_mutex);
 }
 
+static void lo_free_disk(struct gendisk *disk)
+{
+	struct loop_device *lo = disk->private_data;
+
+	mutex_destroy(&lo->lo_mutex);
+	kfree(lo);
+}
+
 static const struct block_device_operations lo_fops = {
 	.owner =	THIS_MODULE,
 	.open =		lo_open,
@@ -1776,6 +1784,7 @@ static const struct block_device_operations lo_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl =	lo_compat_ioctl,
 #endif
+	.free_disk =	lo_free_disk,
 };
 
 /*
@@ -2090,15 +2099,14 @@ static void loop_remove(struct loop_device *lo)
 {
 	/* Make this loop device unreachable from pathname. */
 	del_gendisk(lo->lo_disk);
-	blk_cleanup_disk(lo->lo_disk);
+	blk_cleanup_queue(lo->lo_disk->queue);
 	blk_mq_free_tag_set(&lo->tag_set);
 
 	mutex_lock(&loop_ctl_mutex);
 	idr_remove(&loop_index_idr, lo->lo_number);
 	mutex_unlock(&loop_ctl_mutex);
-	/* There is no route which can find this loop device. */
-	mutex_destroy(&lo->lo_mutex);
-	kfree(lo);
+
+	put_disk(lo->lo_disk);
 }
 
 static void loop_probe(dev_t dev)
-- 
2.35.1