On Tue, Dec 03, 2013 at 04:59:10PM -0800, Andrew Morton wrote: > On Tue, 8 Oct 2013 16:58:10 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > Buffer allocation has a very crude indefinite loop around waking the > > flusher threads and performing global NOFS direct reclaim because it > > can not handle allocation failures. > > > > The most immediate problem with this is that the allocation may fail > > due to a memory cgroup limit, where flushers + direct reclaim might > > not make any progress towards resolving the situation at all. Because > > unlike the global case, a memory cgroup may not have any cache at all, > > only anonymous pages but no swap. This situation will lead to a > > reclaim livelock with insane IO from waking the flushers and thrashing > > unrelated filesystem cache in a tight loop. > > > > Use __GFP_NOFAIL allocations for buffers for now. This makes sure > > that any looping happens in the page allocator, which knows how to > > orchestrate kswapd, direct reclaim, and the flushers sensibly. It > > also allows memory cgroups to detect allocations that can't handle > > failure and will allow them to ultimately bypass the limit if reclaim > > can not make progress. > > Problem. > > > --- a/fs/buffer.c > > +++ b/fs/buffer.c > > @@ -1005,9 +1005,19 @@ grow_dev_page(struct block_device *bdev, sector_t block, > > struct buffer_head *bh; > > sector_t end_block; > > int ret = 0; /* Will call free_more_memory() */ > > + gfp_t gfp_mask; > > > > - page = find_or_create_page(inode->i_mapping, index, > > - (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); > > + gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS; > > + gfp_mask |= __GFP_MOVABLE; > > https://bugzilla.kernel.org/show_bug.cgi?id=65991 > > WARNING: CPU: 0 PID: 1 at mm/page_alloc.c:1539 get_page_from_freelist+0x8a9/0x8c0() > Modules linked in: > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc1 #42 > Hardware name: Acer Aspire 7750G/JE70_HR, BIOS V1.07 03/02/2011 > 0000000000000009 ffff8801c6121650 ffffffff81898d39 0000000000000000 > ffff8801c6121688 ffffffff8107dc43 0000000000000002 0000000000000001 > 0000000000284850 0000000000000000 ffff8801cec04680 ffff8801c6121698 > Call Trace: > [<ffffffff81898d39>] dump_stack+0x4e/0x7a > [<ffffffff8107dc43>] warn_slowpath_common+0x73/0x90 > [<ffffffff8107dd15>] warn_slowpath_null+0x15/0x20 > [<ffffffff81116f69>] get_page_from_freelist+0x8a9/0x8c0 > [<ffffffff81330cdd>] ? trace_hardirqs_off_thunk+0x3a/0x3c > [<ffffffff81117070>] __alloc_pages_nodemask+0xf0/0x770 > [<ffffffff81330cdd>] ? trace_hardirqs_off_thunk+0x3a/0x3c > [<ffffffff81156823>] kmemcheck_alloc_shadow+0x53/0xf0 > [<ffffffff81152495>] new_slab+0x345/0x3e0 > [<ffffffff81897712>] __slab_alloc.isra.57+0x215/0x535 > [<ffffffff81328030>] ? __radix_tree_preload+0x60/0xf0 > [<ffffffff811545c8>] kmem_cache_alloc+0x118/0x150 > [<ffffffff81328030>] ? __radix_tree_preload+0x60/0xf0 > [<ffffffff81328030>] __radix_tree_preload+0x60/0xf0 > [<ffffffff81328125>] radix_tree_maybe_preload+0x25/0x30 > [<ffffffff8110faf7>] add_to_page_cache_locked+0x37/0x100 > [<ffffffff8110fbd5>] add_to_page_cache_lru+0x15/0x40 > [<ffffffff8110ff37>] find_or_create_page+0x57/0x90 > [<ffffffff8118e630>] __getblk+0xf0/0x2f0 > > That __GFP_NOFAIL is getting down into > radix_tree_preload->kmem_cache_alloc() and I expect that in its > boundless stupidity, slab has decided to inappropriately go and use an > unnecessarily massive page size for radix_tree_node_cachep's underlying > memory allocations. So we end up using GFP_NOFAIL for an order=2 (or > more) allocation, which is unacceptably risky, methinks. > > I really really wish slab wouldn't do this. The benefit is surely very > small and these unnecessary higher-order allocations are quite abusive > of the page allocator. > > Can we please make slab stop doing this? > > radix_tree_nodes are 560 bytes and the kernel often allocates them in > times of extreme memory stress. We really really want them to be > backed by order=0 pages. Hello, Andrew. Following patch would fix this problem. Thanks. -------------------8<------------------------ >From 7f21232d1eeffccdbd0f6d79c04d297cf95a713e Mon Sep 17 00:00:00 2001 From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Date: Wed, 4 Dec 2013 10:36:11 +0900 Subject: [PATCH] slub: fix high order page allocation problem with __GFP_NOFAIL 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; + 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); @@ -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); /* * Objects from caches that have a constructor don't get -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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