[PATCH] userns: enable tmpfs support for user namespace.

[PATCH] userns: enable tmpfs support for user namespace.

[Gao feng]

mounting tmpfs in user namespace does no harm to the host.
so enable tmpfs support for the user namespace.

Signed-off-by: Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 mm/shmem.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index d4e184e..ef97dc3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2801,6 +2801,7 @@ static struct file_system_type shmem_fs_type = {
 	.name		= "tmpfs",
 	.mount		= shmem_mount,
 	.kill_sb	= kill_litter_super,
+	.fs_flags	= FS_USERNS_MOUNT,
 };
 
 int __init shmem_init(void)
-- 
1.7.7.6

Re: [PATCH] userns: enable tmpfs support for user namespace.

[Eric W. Biederman]

Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> writes:

> mounting tmpfs in user namespace does no harm to the host.
> so enable tmpfs support for the user namespace.

I think this allows escaping from memory resource limits.

Eric

> Signed-off-by: Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  mm/shmem.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d4e184e..ef97dc3 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2801,6 +2801,7 @@ static struct file_system_type shmem_fs_type = {
>  	.name		= "tmpfs",
>  	.mount		= shmem_mount,
>  	.kill_sb	= kill_litter_super,
> +	.fs_flags	= FS_USERNS_MOUNT,
>  };
>  
>  int __init shmem_init(void)

Re: [PATCH] userns: enable tmpfs support for user namespace.

[Gao feng]

于 2012年09月19日 18:40, Eric W. Biederman 写道:
> Gao feng <gaofeng@cn.fujitsu.com> writes:
> 
>> mounting tmpfs in user namespace does no harm to the host.
>> so enable tmpfs support for the user namespace.
> 
> I think this allows escaping from memory resource limits.
> 

Got it,it makes sense,sorry for the noise.

thanks!
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Re: [PATCH] userns: enable tmpfs support for user namespace.

[Eric W. Biederman]

Gao feng <gaofeng@cn.fujitsu.com> writes:

> 于 2012年09月19日 18:40, Eric W. Biederman 写道:
>> Gao feng <gaofeng@cn.fujitsu.com> writes:
>> 
>>> mounting tmpfs in user namespace does no harm to the host.
>>> so enable tmpfs support for the user namespace.
>> 
>> I think this allows escaping from memory resource limits.
>> 
>
> Got it,it makes sense,sorry for the noise.

No noise problem.

This is a problem that ultimately needs solving.

I putter at that end of my tree from time to time, because those are the
more interesting problems.

Eric
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Re: [PATCH] userns: enable tmpfs support for user namespace.

[Gao feng]

于 2012年09月20日 08:59, Eric W. Biederman 写道:
> Gao feng <gaofeng@cn.fujitsu.com> writes:
> 
>> 于 2012年09月19日 18:40, Eric W. Biederman 写道:
>>> Gao feng <gaofeng@cn.fujitsu.com> writes:
>>>
>>>> mounting tmpfs in user namespace does no harm to the host.
>>>> so enable tmpfs support for the user namespace.
>>>
>>> I think this allows escaping from memory resource limits.
>>>
>>
>> Got it,it makes sense,sorry for the noise.
> 
> No noise problem.
> 
> This is a problem that ultimately needs solving.
> 
> I putter at that end of my tree from time to time, because those are the
> more interesting problems.
> 

Hi Eric

I test the tmpfs with mem cgroup,and found the memory cgroup can limit
how many memory the tasks used through tmpfs.

So I think this problem has already been solved.

Or maybe I misunderstand what you said?

Thanks help from Glauber.

Gao
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