On Thu, 15 Apr 2010 12:05:16 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> I'd like to wait until next mmotm comes out. (So, [RFC]) I'll rebase
> This patch is based on
> mmotm-2010/04/05
> +
> mm-migration-take-a-reference-to-the-anon_vma-before-migrating.patch
> mm-migration-do-not-try-to-migrate-unmapped-anonymous-pages.patch
> mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration.patch
> mm-migration-allow-the-migration-of-pageswapcache-pages.patch
> memcg-fix-prepare-migration.patch
>
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>
> This is an additonal fix to memcg-fix-prepare-migration.patch
>
> Now, try_charge can bypass charge if TIF_MEMDIE at el are marked on the caller.
> In this case, the charge is bypassed. This makes accounts corrupted.
> (PageCgroup will be marked as PCG_USED even if bypassed, and css->refcnt
> can leak.)
>
> This patch clears passed "*memcg" in bypass route.
>
> Because usual page allocater passes memcg=NULL, this patch only affects
> some special case as
> - move account
> - migration
> - swapin.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> Index: mmotm-temp/mm/memcontrol.c
> ===================================================================
> --- mmotm-temp.orig/mm/memcontrol.c
> +++ mmotm-temp/mm/memcontrol.c
> @@ -1606,8 +1606,12 @@ static int __mem_cgroup_try_charge(struc
> * MEMDIE process.
> */
> if (unlikely(test_thread_flag(TIF_MEMDIE)
> - || fatal_signal_pending(current)))
> + || fatal_signal_pending(current))) {
> + /* Showing we skipped charge */
> + if (memcg)
> + *memcg = NULL;
> goto bypass;
> + }
>
I'm sorry, I can't understand what this part fixes.
We set *memcg to NULL at "bypass" part already:
1740 bypass:
1741 *memcg = NULL;
1742 return 0;
and __mem_cgroup_try_charge() is never called with @memcg == NULL, IIUC.
> /*
> * We always charge the cgroup the mm_struct belongs to.
> @@ -2523,7 +2527,6 @@ int mem_cgroup_prepare_migration(struct
> ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false);
> css_put(&mem->css);
> }
> - *ptr = mem;
> return ret;
> }
>
I sent a patch to Andrew to fix this part yesterday :)
Thanks,
Daisuke Nishimura.
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