[PATCH 08/10] mm/slab: Allow dynamic kmalloc() minimum alignment

Catalin Marinas
2022-04-05T23:42:49Z

ARCH_KMALLOC_MINALIGN represents the minimum guaranteed kmalloc()
alignment but an architecture may require a larger run-time alignment.
Do not create kmalloc caches smaller than arch_kmalloc_minalign().

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/slab.h | 2 ++
mm/slab.c | 6 +-----
mm/slab.h | 2 ++
mm/slab_common.c | 33 +++++++++++++++++++++++----------
4 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index d58211bdeceb..2137dba85691 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -332,6 +332,8 @@ enum kmalloc_cache_type {
extern struct kmem_cache *
kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1];

+unsigned int arch_kmalloc_minalign(void);
+
/*
* Define gfp bits that should not be set for KMALLOC_NORMAL.
*/
diff --git a/mm/slab.c b/mm/slab.c
index b04e40078bdf..4aaeeb9c994d 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1256,11 +1256,7 @@ void __init kmem_cache_init(void)
* Initialize the caches that provide memory for the kmem_cache_node
* structures first. Without this, further allocations will bug.
*/
- kmalloc_caches[KMALLOC_NORMAL][INDEX_NODE] = create_kmalloc_cache(
- kmalloc_info[INDEX_NODE].name[KMALLOC_NORMAL],
- kmalloc_info[INDEX_NODE].size,
- ARCH_KMALLOC_FLAGS, 0,
- kmalloc_info[INDEX_NODE].size);
+ new_kmalloc_cache(INDEX_NODE, KMALLOC_NORMAL, ARCH_KMALLOC_FLAGS);
slab_state = PARTIAL_NODE;
setup_kmalloc_cache_index_table();

diff --git a/mm/slab.h b/mm/slab.h
index fd7ae2024897..e9238406602a 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -283,6 +283,8 @@ int __kmem_cache_create(struct kmem_cache *, slab_flags_t flags);
struct kmem_cache *create_kmalloc_cache(const char *name, unsigned int size,
slab_flags_t flags, unsigned int useroffset,
unsigned int usersize);
+void __init new_kmalloc_cache(int idx, enum kmalloc_cache_type type,
+ slab_flags_t flags);
extern void create_boot_cache(struct kmem_cache *, const char *name,
unsigned int size, slab_flags_t flags,
unsigned int useroffset, unsigned int usersize);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 6ee64d6208b3..594d8a8a68d0 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -838,9 +838,18 @@ void __init setup_kmalloc_cache_index_table(void)
}
}

-static void __init
+unsigned int __weak arch_kmalloc_minalign(void)
+{
+ return ARCH_KMALLOC_MINALIGN;
+}
+
+void __init
new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
{
+ unsigned int minalign = arch_kmalloc_minalign();
+ unsigned int aligned_size = kmalloc_info[idx].size;
+ int aligned_idx = idx;
+
if (type == KMALLOC_RECLAIM) {
flags |= SLAB_RECLAIM_ACCOUNT;
} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
@@ -851,10 +860,17 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
flags |= SLAB_ACCOUNT;
}

- kmalloc_caches[type][idx] = create_kmalloc_cache(
- kmalloc_info[idx].name[type],
- kmalloc_info[idx].size, flags, 0,
- kmalloc_info[idx].size);
+ if (minalign > ARCH_KMALLOC_MINALIGN) {
+ aligned_size = ALIGN(aligned_size, minalign);
+ aligned_idx = __kmalloc_index(aligned_size, false);
+ }
+
+ if (!kmalloc_caches[type][aligned_idx])
+ kmalloc_caches[type][aligned_idx] = create_kmalloc_cache(
+ kmalloc_info[aligned_idx].name[type],
+ aligned_size, flags, 0, aligned_size);
+ if (idx != aligned_idx)
+ kmalloc_caches[type][idx] = kmalloc_caches[type][aligned_idx];

/*
* If CONFIG_MEMCG_KMEM is enabled, disable cache merging for
@@ -904,11 +920,8 @@ void __init create_kmalloc_caches(slab_flags_t flags)
struct kmem_cache *s = kmalloc_caches[KMALLOC_NORMAL][i];

if (s) {
- kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
- kmalloc_info[i].name[KMALLOC_DMA],
- kmalloc_info[i].size,
- SLAB_CACHE_DMA | flags, 0,
- kmalloc_info[i].size);
+ new_kmalloc_cache(i, KMALLOC_DMA,
+ SLAB_CACHE_DMA | flags);
}
}
#endif