On Wed, 4 Dec 2013 10:52:18 +0900 Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > SLUB already try to allocate high order page with clearing __GFP_NOFAIL. > But, when allocating shadow page for kmemcheck, it missed clearing > the flag. This trigger WARN_ON_ONCE() reported by Christian Casteyde. > > https://bugzilla.kernel.org/show_bug.cgi?id=65991 > > This patch fix this situation by using same allocation flag as original > allocation. > > Reported-by: Christian Casteyde <casteyde.christian@xxxxxxx> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > diff --git a/mm/slub.c b/mm/slub.c > index 545a170..3dd28b1 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1335,11 +1335,12 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > page = alloc_slab_page(alloc_gfp, node, oo); > if (unlikely(!page)) { > oo = s->min; What is the value of s->min? Please tell me it's zero. > + alloc_gfp = flags; > /* > * Allocation may have failed due to fragmentation. > * Try a lower order alloc if possible > */ > - page = alloc_slab_page(flags, node, oo); > + page = alloc_slab_page(alloc_gfp, node, oo); > > if (page) > stat(s, ORDER_FALLBACK); This change doesn't actually do anything. > @@ -1349,7 +1350,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) { > int pages = 1 << oo_order(oo); > > - kmemcheck_alloc_shadow(page, oo_order(oo), flags, node); > + kmemcheck_alloc_shadow(page, oo_order(oo), alloc_gfp, node); That seems reasonable, assuming kmemcheck can handle the allocation failure. Still I dislike this practice of using unnecessarily large allocations. What does it gain us? Slightly improved object packing density. Anything else? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>