On Wed, 21 Oct 2009, Karol Lewandowski wrote: > commit d6849591e042bceb66f1b4513a1df6740d2ad762 > Author: Karol Lewandowski <[email protected]> > Date: Wed Oct 21 21:01:20 2009 +0200 > > SLUB: Don't drop __GFP_NOFAIL completely from allocate_slab() > > Commit ba52270d18fb17ce2cf176b35419dab1e43fe4a3 unconditionally > cleared __GFP_NOFAIL flag on all allocations. >
No, it clears __GFP_NOFAIL from the first allocation of oo_order(s->oo). If that fails (and it's easy to fail, it has __GFP_NORETRY), another allocation is attempted with oo_order(s->min), for which __GFP_NOFAIL would be preserved if that's the slab cache's allocflags. > Preserve this flag on second attempt to allocate page (with possibly > decreased order). > > This should help with bugs #14265, #14141 and similar. > > Signed-off-by: Karol Lewandowski <[email protected]> > > diff --git a/mm/slub.c b/mm/slub.c > index b627675..ac5db65 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1084,7 +1084,7 @@ static struct page *allocate_slab(struct kmem_cache *s, > gfp_t flags, int node) > { > struct page *page; > struct kmem_cache_order_objects oo = s->oo; > - gfp_t alloc_gfp; > + gfp_t alloc_gfp, nofail; > > flags |= s->allocflags; > > @@ -1092,6 +1092,7 @@ static struct page *allocate_slab(struct kmem_cache *s, > gfp_t flags, int node) > * Let the initial higher-order allocation fail under memory pressure > * so we fall-back to the minimum order allocation. > */ > + nofail = flags & __GFP_NOFAIL; > alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL; > > page = alloc_slab_page(alloc_gfp, node, oo); > @@ -1100,8 +1101,10 @@ static struct page *allocate_slab(struct kmem_cache > *s, gfp_t flags, int node) > /* > * Allocation may have failed due to fragmentation. > * Try a lower order alloc if possible > + * > + * Preserve __GFP_NOFAIL flag if previous allocation failed. > */ > - page = alloc_slab_page(flags, node, oo); > + page = alloc_slab_page(flags | nofail, node, oo); > if (!page) > return NULL; > > This does nothing. You may have missed that the lower order allocation is passing 'flags' (which is a union of the gfp flags passed to allocate_slab() based on the allocation context and the cache's allocflags), and not alloc_gfp where __GFP_NOFAIL is masked. Nack. Note: slub isn't going to be a culprit in order 5 allocation failures since they have kmalloc passthrough to the page allocator. -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
