[PATCH v4 5/5] loop: be paranoid on exit and prevent new additions / removals

[Luis Chamberlain]

Be pedantic on removal as well and hold the mutex.
This should prevent uses of addition while we exit.

I cannot trigger an issue with this though, this is
just a fix done through code inspection.

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
 drivers/block/loop.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 14372df0f354..54fbcbd930de 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2333,6 +2333,8 @@ static void __exit loop_exit(void)
 
 	range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
 
+	mutex_lock(&loop_ctl_mutex);
+
 	idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
 	idr_destroy(&loop_index_idr);
 
@@ -2340,6 +2342,8 @@ static void __exit loop_exit(void)
 	unregister_blkdev(LOOP_MAJOR, "loop");
 
 	misc_deregister(&loop_misc);
+
+	mutex_unlock(&loop_ctl_mutex);
 }
 
 module_init(loop_init);
-- 
2.25.1