[PATCH] null_blk: Fix: memory release when memory_backed=1

[Nitesh Shetty <nj.shetty@xxxxxxxxxxx>]

Memory/pages are not freed, when unloading nullblk driver.

Steps to reproduce issue
  1.free -h
        total        used        free      shared  buff/cache   available
Mem:    7.8Gi       260Mi       7.1Gi       3.0Mi       395Mi       7.3Gi
Swap:      0B          0B          0B
  2.modprobe null_blk memory_backed=1
  3.dd if=/dev/urandom of=/dev/nullb0 oflag=direct bs=1M count=1000
  4.modprobe -r null_blk
  5.free -h
        total        used        free      shared  buff/cache   available
Mem:    7.8Gi       1.2Gi       6.1Gi       3.0Mi       398Mi       6.3Gi
Swap:      0B          0B          0B

Signed-off-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
---

Added a blktest[1] block/034 to test the same issue.
We will raise a PR, if issue is acked and fix is pulled in kernel.

[1] https://github.com/nitesh-shetty/blktests/tree/fix/block/mem_leak
---
 drivers/block/null_blk/main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index b3fedafe301e..864013019d6b 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -2244,6 +2244,7 @@ static void null_destroy_dev(struct nullb *nullb)
 	struct nullb_device *dev = nullb->dev;
 
 	null_del_dev(nullb);
+	null_free_device_storage(dev, false);
 	null_free_dev(dev);
 }
 

base-commit: bc708bbd8260ee4eb3428b0109f5f3be661fae46
-- 
2.35.1.500.gb896f729e2