lkml.org 
[lkml]   [2018]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] memcg: Replace mm->owner with mm->memcg
On 05/04, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@redhat.com> writes:
>
> > On 05/04, Eric W. Biederman wrote:
> >>
> >> Oleg Nesterov <oleg@redhat.com> writes:
> >>
> >> > I'd vote for the change in exec_mmap(). This way mm_init_memcg() can just
> >> > nullify mm->memcg.
> >>
> >> There is at least one common path where we need the memory control group
> >> properly initialized so memory allocations don't escape the memory
> >> control group.
> >>
> >> do_execveat_common
> >> copy_strings
> >> get_arg_page
> >> get_user_pages_remote
> >> __get_user_pages_locked
> >> __get_user_pages
> >> faultin_page
> >> handle_mm_fault
> >> count_memcg_event_mm
> >> __handle_mm_fault
> >> handle_pte_fault
> >> do_anonymous_page
> >> mem_cgroup_try_charge

Ah yes, indeed.

> mm_init_memcg is at the same point as mm_init_owner. So my change did
> not introduce any logic changes on when the memory control group became
> valid.

Not sure, but perhaps I am all confused....

before your patch get_mem_cgroup_from_mm() looks at mm->owner == current
(in this case) and mem_cgroup_from_task() should return the correct memcg
even if execing task migrates after bprm_mm_init(). At least in the common
case when the old mm is not shared.

After your patch the memory allocations in copy_strings() won't be accounted
correctly, bprm->mm->memcg is wrong if this task migrates. And iiuc your recent
"[PATCH 2/2] memcg: Close the race between migration and installing bprm->mm as mm"
doesn't fix the problem.

No?

Perhaps we can change get_mem_cgroup_from_mm() to use
mem_cgroup_from_css(current, memory_cgrp_id) if mm->memcg == NULL?

Oleg.

\
 
 \ /
  Last update: 2018-05-07 16:34    [W:0.247 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site