4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joonsoo Kim <js1304@xxxxxxxxx> commit 03a2d2a3eafe4015412cf4e9675ca0e2d9204074 upstream. Commit description is copied from the original post of this bug: http://comments.gmane.org/gmane.linux.kernel.mm/135349 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): This patch fixes the problem of kmalloc_size(INDEX_NODE + 1) and removes the BUG by adding 'size >= 256' check to guarantee that all necessary small sized slabs are initialized regardless sequence of slab size in mapping table. Fixes: e33660165c90 ("slab: Use common kmalloc_index/kmalloc_size...") Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Reported-by: Liuhailong <liu.hailong6@xxxxxxxxxx> Acked-by: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/slab.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -2190,9 +2190,16 @@ __kmem_cache_create (struct kmem_cache * size += BYTES_PER_WORD; } #if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC) - if (size >= kmalloc_size(INDEX_NODE + 1) - && cachep->object_size > cache_line_size() - && ALIGN(size, cachep->align) < PAGE_SIZE) { + /* + * To activate debug pagealloc, off-slab management is necessary + * requirement. In early phase of initialization, small sized slab + * doesn't get initialized so it would not be possible. So, we need + * to check size >= 256. It guarantees that all necessary small + * sized slab is initialized in current slab initialization sequence. + */ + if (!slab_early_init && size >= kmalloc_size(INDEX_NODE) && + size >= 256 && cachep->object_size > cache_line_size() && + ALIGN(size, cachep->align) < PAGE_SIZE) { cachep->obj_offset += PAGE_SIZE - ALIGN(size, cachep->align); size = PAGE_SIZE; } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html