kmem_cache_create() is a pretty big function, so we'll devote one whole
patch just to cleaning it up.
-Matt
General readability fixes.
* Replace a constant (4096) with a named #define (RED_ZONE_LIMIT)
* Reformat a looong if statement
* Replace a confusing label (opps) with a more sensible one (out)
* Rewrite some confusing slab alignment code for readability
* Replace a list_for_each/list_entry combo with an identical but
more readable list_for_each_entry loop.
Signed-off-by: Matthew Dobson <[email protected]>
Index: linux-2.6.14+slab_cleanup/mm/slab.c
===================================================================
--- linux-2.6.14+slab_cleanup.orig/mm/slab.c 2005-11-10 11:48:43.827192216 -0800
+++ linux-2.6.14+slab_cleanup/mm/slab.c 2005-11-10 11:48:47.540627688 -0800
@@ -491,6 +491,9 @@ struct kmem_cache_s {
#define POISON_FREE 0x6b /* for use-after-free poisoning */
#define POISON_END 0xa5 /* end-byte of poisoning */
+/* Don't use red zoning for ojects greater than this size */
+#define RED_ZONE_LIMIT 4096
+
/*
* memory layout of objects:
* 0 : objp
@@ -1547,21 +1550,18 @@ kmem_cache_t *kmem_cache_create(const ch
void (*ctor)(void *, kmem_cache_t *, unsigned long),
void (*dtor)(void *, kmem_cache_t *, unsigned long))
{
- size_t left_over, slab_size, ralign;
+ size_t left_over, slab_size, aligned_slab_size, ralign;
kmem_cache_t *cachep = NULL;
/*
* Sanity checks... these are all serious usage bugs.
*/
- if ((!name) ||
- in_interrupt() ||
- (size < BYTES_PER_WORD) ||
- (size > (1<<MAX_OBJ_ORDER)*PAGE_SIZE) ||
- (dtor && !ctor)) {
- printk(KERN_ERR "%s: Early error in slab %s\n",
- __FUNCTION__, name);
- BUG();
- }
+ if (!name || in_interrupt() || (size < BYTES_PER_WORD) ||
+ (size > (1 << MAX_OBJ_ORDER) * PAGE_SIZE) || (dtor && !ctor)) {
+ printk(KERN_ERR "%s: Early error in slab %s\n",
+ __FUNCTION__, name);
+ BUG();
+ }
#if DEBUG
WARN_ON(strchr(name, ' ')); /* It confuses parsers */
@@ -1579,7 +1579,8 @@ kmem_cache_t *kmem_cache_create(const ch
* above the next power of two: caches with object sizes just above a
* power of two have a significant amount of internal fragmentation.
*/
- if (size < 4096 || fls(size - 1) == fls(size - 1 + 3 * BYTES_PER_WORD))
+ if (size < RED_ZONE_LIMIT ||
+ fls(size - 1) == fls(size - 1 + 3 * BYTES_PER_WORD))
flags |= SLAB_RED_ZONE|SLAB_STORE_USER;
if (!(flags & SLAB_DESTROY_BY_RCU))
flags |= SLAB_POISON;
@@ -1642,7 +1643,7 @@ kmem_cache_t *kmem_cache_create(const ch
/* Get cache's description obj. */
cachep = (kmem_cache_t *) kmem_cache_alloc(&cache_cache, SLAB_KERNEL);
if (!cachep)
- goto opps;
+ goto out;
memset(cachep, 0, sizeof(kmem_cache_t));
#if DEBUG
@@ -1700,24 +1701,22 @@ kmem_cache_t *kmem_cache_create(const ch
printk("kmem_cache_create: couldn't create cache %s.\n", name);
kmem_cache_free(&cache_cache, cachep);
cachep = NULL;
- goto opps;
+ goto out;
}
- slab_size = ALIGN(cachep->num*sizeof(kmem_bufctl_t)
- + sizeof(struct slab), align);
+ slab_size = cachep->num * sizeof(kmem_bufctl_t) + sizeof(struct slab);
+ aligned_slab_size = ALIGN(slab_size, align);
/*
* If the slab has been placed off-slab, and we have enough space then
* move it on-slab. This is at the expense of any extra colouring.
*/
- if (flags & CFLGS_OFF_SLAB && left_over >= slab_size) {
+ if (flags & CFLGS_OFF_SLAB && left_over >= aligned_slab_size) {
flags &= ~CFLGS_OFF_SLAB;
- left_over -= slab_size;
- }
-
- if (flags & CFLGS_OFF_SLAB) {
- /* really off slab. No need for manual alignment */
- slab_size = cachep->num*sizeof(kmem_bufctl_t)+sizeof(struct slab);
+ left_over -= aligned_slab_size;
}
+ /* On slab, need manual alignment */
+ if (!(flags & CFLGS_OFF_SLAB))
+ slab_size = aligned_slab_size;
cachep->colour_off = cache_line_size();
/* Offset must be a multiple of the alignment. */
@@ -1799,13 +1798,12 @@ kmem_cache_t *kmem_cache_create(const ch
/* Need the semaphore to access the chain. */
down(&cache_chain_sem);
{
- struct list_head *p;
+ kmem_cache_t *pc;
mm_segment_t old_fs;
old_fs = get_fs();
set_fs(KERNEL_DS);
- list_for_each(p, &cache_chain) {
- kmem_cache_t *pc = list_entry(p, kmem_cache_t, next);
+ list_for_each_entry(pc, &cache_chain, next) {
char tmp;
/*
* This happens when the module gets unloaded & doesn't
@@ -1832,10 +1830,9 @@ kmem_cache_t *kmem_cache_create(const ch
list_add(&cachep->next, &cache_chain);
up(&cache_chain_sem);
unlock_cpu_hotplug();
-opps:
+out:
if (!cachep && (flags & SLAB_PANIC))
- panic("kmem_cache_create(): failed to create slab `%s'\n",
- name);
+ panic("%s: failed to create slab `%s'\n", __FUNCTION__, name);
return cachep;
}
EXPORT_SYMBOL(kmem_cache_create);
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