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* [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU
@ 2019-05-24  8:06 Sahitya Tummala
  2019-05-24 14:15 ` Yafang Shao
  2019-05-24 16:52 ` Theodore Ts'o
  0 siblings, 2 replies; 3+ messages in thread
From: Sahitya Tummala @ 2019-05-24  8:06 UTC (permalink / raw)
  To: Andrew Morton, Kirill Tkhai, Michal Hocko, Johannes Weiner,
	Vladimir Davydov, Yafang Shao, Roman Gushchin, Mel Gorman,
	linux-mm, Theodore Y. Ts'o, Jaegeuk Kim, Eric Biggers,
	linux-fscrypt
  Cc: linux-kernel, Sahitya Tummala

This is important for the scenario where FBE (file based encryption)
is enabled. With FBE, the encryption context needed to en/decrypt a file
will be stored in inode and any inode that is left in the cache after
drop_caches is done will be a problem. For ex, in Android, drop_caches
will be used when switching work profiles.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d96c547..b48926f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -730,7 +730,7 @@ void drop_slab_node(int nid)
 		do {
 			freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
 		} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
-	} while (freed > 10);
+	} while (freed != 0);
 }
 
 void drop_slab(void)
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU
  2019-05-24  8:06 [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU Sahitya Tummala
@ 2019-05-24 14:15 ` Yafang Shao
  2019-05-24 16:52 ` Theodore Ts'o
  1 sibling, 0 replies; 3+ messages in thread
From: Yafang Shao @ 2019-05-24 14:15 UTC (permalink / raw)
  To: Sahitya Tummala
  Cc: Andrew Morton, Kirill Tkhai, Michal Hocko, Johannes Weiner,
	Vladimir Davydov, Roman Gushchin, Mel Gorman, Linux MM,
	Theodore Y. Ts'o, Jaegeuk Kim, Eric Biggers, linux-fscrypt,
	LKML

On Fri, May 24, 2019 at 4:06 PM Sahitya Tummala <stummala@codeaurora.org> wrote:
>
> This is important for the scenario where FBE (file based encryption)
> is enabled. With FBE, the encryption context needed to en/decrypt a file
> will be stored in inode and any inode that is left in the cache after
> drop_caches is done will be a problem. For ex, in Android, drop_caches
> will be used when switching work profiles.
>
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> ---
>  mm/vmscan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d96c547..b48926f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -730,7 +730,7 @@ void drop_slab_node(int nid)
>                 do {
>                         freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
>                 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
> -       } while (freed > 10);
> +       } while (freed != 0);
>  }

Perhaps that is not enough, because the shrink may stop when scan
count is less than SHRINK_BATCH.
Pls. see do_shrink_slab.

What about set shrinker->batch to 1 in this case ?

Thanks
Yafang

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU
  2019-05-24  8:06 [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU Sahitya Tummala
  2019-05-24 14:15 ` Yafang Shao
@ 2019-05-24 16:52 ` Theodore Ts'o
  1 sibling, 0 replies; 3+ messages in thread
From: Theodore Ts'o @ 2019-05-24 16:52 UTC (permalink / raw)
  To: Sahitya Tummala
  Cc: Andrew Morton, Kirill Tkhai, Michal Hocko, Johannes Weiner,
	Vladimir Davydov, Yafang Shao, Roman Gushchin, Mel Gorman,
	linux-mm, Jaegeuk Kim, Eric Biggers, linux-fscrypt, linux-kernel

On Fri, May 24, 2019 at 01:36:01PM +0530, Sahitya Tummala wrote:
> This is important for the scenario where FBE (file based encryption)
> is enabled. With FBE, the encryption context needed to en/decrypt a file
> will be stored in inode and any inode that is left in the cache after
> drop_caches is done will be a problem. For ex, in Android, drop_caches
> will be used when switching work profiles.
> 
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>

Instead of making a change to vmscan.c, it's probably better to
migrate to the new fscrypt key-management framework, which solves this
problem with an explicit FS_IOC_REMOVE_ENCRYPTION_KEY ioctl.  This
allows the system to remove all inodes that were made available via a
single key without having nuking all other inodes --- this would make
it much faster after a user logs out of ChromeOS, for example:

See:

	https://patchwork.kernel.org/patch/10952019/

							- Ted

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2019-05-24 16:52 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2019-05-24  8:06 [PATCH] mm/vmscan.c: drop all inode/dentry cache from LRU Sahitya Tummala
2019-05-24 14:15 ` Yafang Shao
2019-05-24 16:52 ` Theodore Ts'o

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