[PATCH 5.18 087/879] loop: implement ->free_disk

Greg Kroah-Hartman
2022-06-07T22:11:47Z

From: Christoph Hellwig <hch@lst.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@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.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