mm: slab: only move management objects off-slab for sizes larger than KMALLOC_MIN_SIZE
On systems with a KMALLOC_MIN_SIZE of 128 (arm64, some mips and powerpc configurations defining ARCH_DMA_MINALIGN to 128), the first kmalloc_caches[] entry to be initialised after slab_early_init = 0 is "kmalloc-128" with index 7. Depending on the debug kernel configuration, sizeof(struct kmem_cache) can be larger than 128 resulting in an INDEX_NODE of 8. Commit8fc9cf420b
("slab: make more slab management structure off the slab") enables off-slab management objects for sizes starting with PAGE_SIZE >> 5 (128 bytes for a 4KB page configuration) and the creation of the "kmalloc-128" cache would try to place the management objects off-slab. However, since KMALLOC_MIN_SIZE is already 128 and freelist_size == 32 in __kmem_cache_create(), kmalloc_slab(freelist_size) returns NULL (kmalloc_caches[7] not populated yet). This triggers the following bug on arm64: kernel BUG at /work/Linux/linux-2.6-aarch64/mm/slab.c:2283! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 4.3.0-rc4+ #540 Hardware name: Juno (DT) PC is at __kmem_cache_create+0x21c/0x280 LR is at __kmem_cache_create+0x210/0x280 [...] Call trace: __kmem_cache_create+0x21c/0x280 create_boot_cache+0x48/0x80 create_kmalloc_cache+0x50/0x88 create_kmalloc_caches+0x4c/0xf4 kmem_cache_init+0x100/0x118 start_kernel+0x214/0x33c This patch introduces an OFF_SLAB_MIN_SIZE definition to avoid off-slab management objects for sizes equal to or smaller than KMALLOC_MIN_SIZE. Fixes:8fc9cf420b
("slab: make more slab management structure off the slab") Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: <stable@vger.kernel.org> [3.15+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -282,6 +282,7 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent)
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#define CFLGS_OFF_SLAB (0x80000000UL)
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#define OFF_SLAB(x) ((x)->flags & CFLGS_OFF_SLAB)
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#define OFF_SLAB_MIN_SIZE (max_t(size_t, PAGE_SIZE >> 5, KMALLOC_MIN_SIZE + 1))
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#define BATCHREFILL_LIMIT 16
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/*
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@ -2212,7 +2213,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
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* it too early on. Always use on-slab management when
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* SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
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*/
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if ((size >= (PAGE_SIZE >> 5)) && !slab_early_init &&
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if (size >= OFF_SLAB_MIN_SIZE && !slab_early_init &&
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!(flags & SLAB_NOLEAKTRACE))
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/*
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* Size is large, assume best to place the slab management obj
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@ -2276,7 +2277,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
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/*
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* This is a possibility for one of the kmalloc_{dma,}_caches.
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* But since we go off slab only for object size greater than
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* PAGE_SIZE/8, and kmalloc_{dma,}_caches get created
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* OFF_SLAB_MIN_SIZE, and kmalloc_{dma,}_caches get created
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* in ascending order,this should not happen at all.
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* But leave a BUG_ON for some lucky dude.
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*/
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