Messages in this thread | | | Date | Thu, 27 Oct 2016 09:25:18 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH v1] memcg: Prevent caches to be both OFF_SLAB & OBJFREELIST_SLAB |
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The patch is marked for memcg but I do not see any direct relation. I am not familiar with this code enough probably but if this really is memcg kmem related, please do not forget to CC Vladimir
On Wed 26-10-16 10:41:28, Thomas Garnier wrote: > While testing OBJFREELIST_SLAB integration with pagealloc, we found a > bug where kmem_cache(sys) would be created with both CFLGS_OFF_SLAB & > CFLGS_OBJFREELIST_SLAB. > > The original kmem_cache is created early making OFF_SLAB not possible. > When kmem_cache(sys) is created, OFF_SLAB is possible and if pagealloc > is enabled it will try to enable it first under certain conditions. > Given kmem_cache(sys) reuses the original flag, you can have both flags > at the same time resulting in allocation failures and odd behaviors. > > The proposed fix removes these flags by default at the entrance of > __kmem_cache_create. This way the function will define which way the > freelist should be handled at this stage for the new cache. > > Fixes: b03a017bebc4 ("mm/slab: introduce new slab management type, OBJFREELIST_SLAB") > Signed-off-by: Thomas Garnier <thgarnie@google.com> > Signed-off-by: Greg Thelen <gthelen@google.com> > --- > Based on next-20161025 > --- > mm/slab.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/slab.c b/mm/slab.c > index 3c83c29..efe280a 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -2027,6 +2027,14 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) > int err; > size_t size = cachep->size; > > + /* > + * memcg re-creates caches with the flags of the originals. Remove > + * the freelist related flags to ensure they are re-defined at this > + * stage. Prevent having both flags on edge cases like with pagealloc > + * if the original cache was created too early to be OFF_SLAB. > + */ > + flags &= ~(CFLGS_OBJFREELIST_SLAB|CFLGS_OFF_SLAB); > + > #if DEBUG > #if FORCED_DEBUG > /* > -- > 2.8.0.rc3.226.g39d4020 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs
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