The patch titled
Subject: slab: fix unexpected index mapping result of kmalloc_size(INDEX_NODE + 1)
has been added to the -mm tree. Its filename is
slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1.patch
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From: Liuhailong <liu.hailong6@xxxxxxxxxx>
Subject: slab: fix unexpected index mapping result of kmalloc_size(INDEX_NODE + 1)
Kernels after v3.9 use kmalloc_size(INDEX_NODE + 1) to get the next larger
cache size than the size index INDEX_NODE mapping. In kernels 3.9 and
earlier we used malloc_sizes[INDEX_L3 + 1].cs_size.
However, sometimes we can't get the right output we expected via
kmalloc_size(INDEX_NODE + 1), causing a BUG().
The mapping table in the latest kernel is like:
index = {0, 1, 2 , 3, 4, 5, 6, n}
size = {0, 96, 192, 8, 16, 32, 64, 2^n}
The mapping table before 3.10 is like this:
index = {0 , 1 , 2, 3, 4 , 5 , 6, n}
size = {32, 64, 96, 128, 192, 256, 512, 2^(n+3)}
The problem on my mips64 machine is as follows:
(1) When configured DEBUG_SLAB && DEBUG_PAGEALLOC && DEBUG_LOCK_ALLOC
&& DEBUG_SPINLOCK, the sizeof(struct kmem_cache_node) will be "150",
and the macro INDEX_NODE turns out to be "2": #define INDEX_NODE
kmalloc_index(sizeof(struct kmem_cache_node))
(2) Then the result of kmalloc_size(INDEX_NODE + 1) is 8.
(3) Then "if(size >= kmalloc_size(INDEX_NODE + 1)" will lead to "size
= PAGE_SIZE".
(4) Then "if ((size >= (PAGE_SIZE >> 3))" test will be satisfied and
"flags |= CFLGS_OFF_SLAB" will be covered.
(5) if (flags & CFLGS_OFF_SLAB)" test will be satisfied and will go to
"cachep->slabp_cache = kmalloc_slab(slab_size, 0u)", and the result
here may be NULL while kernel bootup.
(6) Finally,"BUG_ON(ZERO_OR_NULL_PTR(cachep->slabp_cache));" causes the
BUG info as the following shows (may be only mips64 has this problem):
#20
task: ffffffffc072cdc0 ti: ffffffffc06b4000 task.ti: ffffffffc06b4000
$ 0 : 0000000000000000 0000000000000018 0000000000000001 0000000100000fff
$ 4 : 0000000000000030 0000000000000000 0000000000001004 0000000000001000
$ 8 : ffffffff80002800 000000000000000b 0000000000000000 0000000000000000
$12 : 0000000080000000 0000000000000000 c0000000bf818ebc c0000000bf818eb8
$16 : c0000000bf818ea0 0000000080002800 0000000000000000 0000000000001000
$20 : 0000000000000034 0000000080000000 0000000000000000 0000000000000006
$24 : ffffffffc1160000 00000000000003f4
$28 : ffffffffc06b4000 ffffffffc06b7d40 0000000000002000 ffffffffc01d077c
Hi : 0000000000000fff
Lo : 0000000000100000
epc : ffffffffc01d0784 __kmem_cache_create+0x2ac/0x530
Not tainted
ra : ffffffffc01d077c __kmem_cache_create+0x2a4/0x530
Status: 141000e2 KX SX UX KERNEL EXL
Cause : 40808034
PrId : 000c1300 (Broadcom XLPII)
Process swapper (pid: 0, threadinfo=ffffffffc06b4000, task=ffffffffc072cdc
0,tls=0000000000000000)
*HwTLS: fffffffffadebeef
Stack : 00000000c073b018 c0000000bf818ea0 0000000000000040 0000000000000000
ffffffffc115b360 ffffffffc115b360 0000000000000017 0000000000000007
0000000000000006 ffffffffc0780f54 0000000000002000 0000000000000040
c0000000bf818ea0 0000000000000000 0000000000000040 ffffffffc0780fec
0000000000002000 c0000000bf810fc0 ffffffffc115b390 0000000000000006
ffffffffc1160000 ffffffffc07810b0 0000000000000001 c0000000bf809000
ffffffffc0a30000 ffffffffc07a0000 ffffffffc07a1758 ffffffffc0a30000
ffffffff8c190000 ffffffff8bd02983 0000000000000000 ffffffff8c18f798
0000000000000000 ffffffffc07746e0 ffffffffc07a1758 0000000000000000
0000000000000000 ffffffff805c5580 0000000000000000 0000000000000000
...
Call Trace:
[<ffffffffc01d0784>] __kmem_cache_create+0x2ac/0x530
[<ffffffffc0780f54>] create_boot_cache+0x54/0x90
[<ffffffffc0780fec>] create_kmalloc_cache+0x5c/0x94
[<ffffffffc07810b0>] create_kmalloc_caches+0x8c/0x1b0
[<ffffffffc07746e0>] start_kernel+0x1a0/0x408
This patch fixes the problem of kmalloc_size(INDEX_NODE + 1) removes the
BUG. I tested it on my mips64 mechine.
Signed-off-by: Liuhailong <liu.hailong6@xxxxxxxxxx>
Reviewed-by: Jianxuexin <jiang.xuexin@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/slab.c~slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1 mm/slab.c
--- a/mm/slab.c~slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1
+++ a/mm/slab.c
@@ -2190,7 +2190,7 @@ __kmem_cache_create (struct kmem_cache *
size += BYTES_PER_WORD;
}
#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
- if (size >= kmalloc_size(INDEX_NODE + 1)
+ if (size >= kmalloc_size(INDEX_NODE) * 2
&& cachep->object_size > cache_line_size()
&& ALIGN(size, cachep->align) < PAGE_SIZE) {
cachep->obj_offset += PAGE_SIZE - ALIGN(size, cachep->align);
_
Patches currently in -mm which might be from liu.hailong6@xxxxxxxxxx are
slab-fix-the-unexpected-index-mapping-result-of-kmalloc_sizeindex_node-1.patch
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