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Date: Fri, 6 Nov 2015 14:00:55 +0100 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Catalin Marinas <catalin.marinas@....com> Cc: Andrew Morton <akpm@...ux-foundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Pekka Enberg <penberg@...nel.org>, Linux MM <linux-mm@...ck.org>, David Rientjes <rientjes@...gle.com>, Christoph Lameter <cl@...ux.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH] mm: slab: Only move management objects off-slab for sizes larger than KMALLOC_MIN_SIZE On Thu, Nov 5, 2015 at 5:08 PM, Catalin Marinas <catalin.marinas@....com> wrote: > From fda8f306b6941f4ddbefcbcfaa59fedef4a679a3 Mon Sep 17 00:00:00 2001 > From: Catalin Marinas <catalin.marinas@....com> > Date: Thu, 5 Nov 2015 11:14:48 +0000 > Subject: [PATCH] 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. > > Commit 8fc9cf420b36 ("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: > > [ 0.000000] kernel BUG at /work/Linux/linux-2.6-aarch64/mm/slab.c:2283! > [ 0.000000] Internal error: Oops - BUG: 0 [#1] SMP > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.3.0-rc4+ #540 > [ 0.000000] Hardware name: Juno (DT) > [ 0.000000] task: ffffffc0006962b0 ti: ffffffc00068c000 task.ti: ffffffc00068c000 > [ 0.000000] PC is at __kmem_cache_create+0x21c/0x280 > [ 0.000000] LR is at __kmem_cache_create+0x210/0x280 > [...] > [ 0.000000] Call trace: > [ 0.000000] [<ffffffc000154948>] __kmem_cache_create+0x21c/0x280 > [ 0.000000] [<ffffffc000652da4>] create_boot_cache+0x48/0x80 > [ 0.000000] [<ffffffc000652e2c>] create_kmalloc_cache+0x50/0x88 > [ 0.000000] [<ffffffc000652f14>] create_kmalloc_caches+0x4c/0xf4 > [ 0.000000] [<ffffffc000654a9c>] kmem_cache_init+0x100/0x118 > [ 0.000000] [<ffffffc0006447d4>] 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: 8fc9cf420b36 ("slab: make more slab management structure off the slab") > Cc: <stable@...r.kernel.org> # 3.15+ > Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org> > Cc: Christoph Lameter <cl@...ux.com> > Cc: Pekka Enberg <penberg@...nel.org> > Cc: David Rientjes <rientjes@...gle.com> > Cc: Joonsoo Kim <iamjoonsoo.kim@....com> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Signed-off-by: Catalin Marinas <catalin.marinas@....com> Thanks a lot! For the record (the fix is already upstream): Tested-by: Geert Uytterhoeven <geert+renesas@...der.be> Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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