2023-06-05 06:55:24

by Nitesh Shetty

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

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 <[email protected]>
Signed-off-by: Nitesh Shetty <[email protected]>
---

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

2023-06-05 22:39:04

by Jens Axboe

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

On Mon, 05 Jun 2023 11:53:53 +0530, Nitesh Shetty wrote:
> 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
>
> [...]

Applied, thanks!

[1/1] null_blk: Fix: memory release when memory_backed=1
commit: 8cfb98196cceec35416041c6b91212d2b99392e4

Best regards,
--
Jens Axboe