On Fri, Dec 23, 2016 at 12:30:02PM -0600, Christoph Lameter wrote:
>
> On Fri, 23 Dec 2016, Grygorii Maistrenko wrote:
>
> > In case CONFIG_SLUB_DEBUG_ON=n find_mergeable() gets debug features
> > from commandline but never checks if there are features from the
> > SLAB_NEVER_MERGE set.
> > As a result selected by slub_debug caches are always mergeable if they
> > have been created without a custom constructor set or without one of the
> > SLAB_* debug features on.
>
> WTF is this nonsense? That check is done a few lines earlier!
>
> struct kmem_cache *ind_mergeable(size_t size, size_t align,
> unsigned long flags, const char *name, void (*ctor)(void *))
> {
> struct kmem_cache *s;
>
> if (slab_nomerge || (flags & SLAB_NEVER_MERGE)) <----- !!!!!!
> return NULL;
This one check is done on flags passed to kmem_cache_create().
>
> if (ctor)
> return NULL;
>
> size = ALIGN(size, sizeof(void *));
> align = calculate_alignment(flags,
flags = kmem_cache_flags(size, flags, name, NULL);
I added here the missing line. This updates flags from commandline and
after this we do not check it.
>
>
> >
> > This adds the necessary check and makes selected slab caches unmergeable
> > if one of the SLAB_NEVER_MERGE features is set from commandline.
> >
> > Signed-off-by: Grygorii Maistrenko <grygoriimkd@xxxxxxxxx>
> > ---
> > mm/slab_common.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index 329b03843863..7341cba8c58b 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -266,6 +266,9 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
> > size = ALIGN(size, align);
> > flags = kmem_cache_flags(size, flags, name, NULL);
> >
> > + if (flags & SLAB_NEVER_MERGE)
> > + return NULL;
> > +
> > list_for_each_entry_reverse(s, &slab_caches, list) {
> > if (slab_unmergeable(s))
> > continue;
> >
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