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authorDaniel Sanders <daniel.sanders@imgtec.com>2015-06-24 16:55:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-24 17:49:41 -0700
commit34cc6990d4d2d85f60e583ebe3070f8c3ada465c (patch)
tree879fe0ea49cd8eb477ec526816e77240e669ab5e /mm/slab.h
parent4066c33d0308f87e9a3b0c7fafb9141c0bfbfa77 (diff)
slab: correct size_index table before replacing the bootstrap kmem_cache_node
This patch moves the initialization of the size_index table slightly earlier so that the first few kmem_cache_node's can be safely allocated when KMALLOC_MIN_SIZE is large. There are currently two ways to generate indices into kmalloc_caches (via kmalloc_index() and via the size_index table in slab_common.c) and on some arches (possibly only MIPS) they potentially disagree with each other until create_kmalloc_caches() has been called. It seems that the intention is that the size_index table is a fast equivalent to kmalloc_index() and that create_kmalloc_caches() patches the table to return the correct value for the cases where kmalloc_index()'s if-statements apply. The failing sequence was: * kmalloc_caches contains NULL elements * kmem_cache_init initialises the element that 'struct kmem_cache_node' will be allocated to. For 32-bit Mips, this is a 56-byte struct and kmalloc_index returns KMALLOC_SHIFT_LOW (7). * init_list is called which calls kmalloc_node to allocate a 'struct kmem_cache_node'. * kmalloc_slab selects the kmem_caches element using size_index[size_index_elem(size)]. For MIPS, size is 56, and the expression returns 6. * This element of kmalloc_caches is NULL and allocation fails. * If it had not already failed, it would have called create_kmalloc_caches() at this point which would have changed size_index[size_index_elem(size)] to 7. I don't believe the bug to be LLVM specific but GCC doesn't normally encounter the problem. I haven't been able to identify exactly what GCC is doing better (probably inlining) but it seems that GCC is managing to optimize to the point that it eliminates the problematic allocations. This theory is supported by the fact that GCC can be made to fail in the same way by changing inline, __inline, __inline__, and __always_inline in include/linux/compiler-gcc.h such that they don't actually inline things. Signed-off-by: Daniel Sanders <daniel.sanders@imgtec.com> Acked-by: Pekka Enberg <penberg@kernel.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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab.h')
-rw-r--r--mm/slab.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/slab.h b/mm/slab.h
index 4c3ac12dd644..8da63e4e470f 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -71,6 +71,7 @@ unsigned long calculate_alignment(unsigned long flags,
#ifndef CONFIG_SLOB
/* Kmalloc array related functions */
+void setup_kmalloc_cache_index_table(void);
void create_kmalloc_caches(unsigned long);
/* Find the kmalloc slab corresponding for a certain size */