slab: Handle ARCH_DMA_MINALIGN correctly
James Hogan hit boot problems in next-20130204 on Meta:
META213-Thread0 DSP [LogF] kobject (4fc03980): tried to init an initialized object, something is seriously wrong.
META213-Thread0 DSP [LogF]
META213-Thread0 DSP [LogF] Call trace:
META213-Thread0 DSP [LogF] [<4000888c>] _show_stack+0x68/0x7c
META213-Thread0 DSP [LogF] [<400088b4>] _dump_stack+0x14/0x28
META213-Thread0 DSP [LogF] [<40103794>] _kobject_init+0x58/0x9c
META213-Thread0 DSP [LogF] [<40103810>] _kobject_create+0x38/0x64
META213-Thread0 DSP [LogF] [<40103eac>] _kobject_create_and_add+0x14/0x8c
META213-Thread0 DSP [LogF] [<40190ac4>] _mnt_init+0xd8/0x220
META213-Thread0 DSP [LogF] [<40190508>] _vfs_caches_init+0xb0/0x160
META213-Thread0 DSP [LogF] [<401851f4>] _start_kernel+0x274/0x340
META213-Thread0 DSP [LogF] [<40188424>] _metag_start_kernel+0x58/0x6c
META213-Thread0 DSP [LogF] [<40000044>] __start+0x44/0x48
META213-Thread0 DSP [LogF]
META213-Thread0 DSP [LogF] devtmpfs: initialized
META213-Thread0 DSP [LogF] L2 Cache: Not present
META213-Thread0 DSP [LogF] BUG: failure at fs/sysfs/dir.c:736/sysfs_read_ns_type()!
META213-Thread0 DSP [LogF] Kernel panic - not syncing: BUG!
META213-Thread0 DSP [Thread Exit] Thread has exited - return code = 4294967295
And bisected the problem to commit 95a05b4 ("slab: Common constants for
kmalloc boundaries").
As it turns out, a fixed KMALLOC_SHIFT_LOW does not work for arches with
higher alignment requirements.
Determine KMALLOC_SHIFT_LOW from ARCH_DMA_MINALIGN instead.
Reported-and-tested-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/include/linux/slab.h b/include/linux/slab.h
index f2327a8..0c62175 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -133,6 +133,19 @@
void kzfree(const void *);
size_t ksize(const void *);
+/*
+ * Some archs want to perform DMA into kmalloc caches and need a guaranteed
+ * alignment larger than the alignment of a 64-bit integer.
+ * Setting ARCH_KMALLOC_MINALIGN in arch headers allows that.
+ */
+#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
+#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
+#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
+#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN)
+#else
+#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
+#endif
+
#ifdef CONFIG_SLOB
/*
* Common fields provided in kmem_cache by all slab allocators
@@ -179,7 +192,9 @@
#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
(MAX_ORDER + PAGE_SHIFT - 1) : 25)
#define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH
+#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 5
+#endif
#else
/*
* SLUB allocates up to order 2 pages directly and otherwise
@@ -187,8 +202,10 @@
*/
#define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT)
+#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 3
#endif
+#endif
/* Maximum allocatable size */
#define KMALLOC_MAX_SIZE (1UL << KMALLOC_SHIFT_MAX)
@@ -200,9 +217,7 @@
/*
* Kmalloc subsystem.
*/
-#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
-#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
-#else
+#ifndef KMALLOC_MIN_SIZE
#define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW)
#endif
@@ -290,17 +305,6 @@
#endif /* !CONFIG_SLOB */
/*
- * Some archs want to perform DMA into kmalloc caches and need a guaranteed
- * alignment larger than the alignment of a 64-bit integer.
- * Setting ARCH_KMALLOC_MINALIGN in arch headers allows that.
- */
-#ifdef ARCH_DMA_MINALIGN
-#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
-#else
-#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
-#endif
-
-/*
* Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
* Intended for arches that get misalignment faults even for 64 bit integer
* aligned buffers.