2006-01-08 02:01:45 -07:00
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/*
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* SLOB Allocator: Simple List Of Blocks
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*
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* Matt Mackall <mpm@selenic.com> 12/30/03
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*
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* How SLOB works:
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*
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* The core of SLOB is a traditional K&R style heap allocator, with
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* support for returning aligned objects. The granularity of this
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* allocator is 8 bytes on x86, though it's perhaps possible to reduce
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* this to 4 if it's deemed worth the effort. The slob heap is a
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* singly-linked list of pages from __get_free_page, grown on demand
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* and allocation from the heap is currently first-fit.
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*
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* Above this is an implementation of kmalloc/kfree. Blocks returned
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* from kmalloc are 8-byte aligned and prepended with a 8-byte header.
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* If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
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* __get_free_pages directly so that it can return page-aligned blocks
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* and keeps a linked list of such pages and their orders. These
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* objects are detected in kfree() by their page alignment.
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*
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* SLAB is emulated on top of SLOB by simply calling constructors and
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* destructors for every SLAB allocation. Objects are returned with
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* the 8-byte alignment unless the SLAB_MUST_HWCACHE_ALIGN flag is
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* set, in which case the low-level allocator will fragment blocks to
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* create the proper alignment. Again, objects of page-size or greater
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* are allocated by calling __get_free_pages. As SLAB objects know
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* their size, no separate size bookkeeping is necessary and there is
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* essentially no allocation space overhead.
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*/
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#include <linux/slab.h>
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#include <linux/mm.h>
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#include <linux/cache.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/timer.h>
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struct slob_block {
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int units;
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struct slob_block *next;
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};
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typedef struct slob_block slob_t;
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#define SLOB_UNIT sizeof(slob_t)
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#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
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#define SLOB_ALIGN L1_CACHE_BYTES
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struct bigblock {
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int order;
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void *pages;
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struct bigblock *next;
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};
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typedef struct bigblock bigblock_t;
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static slob_t arena = { .next = &arena, .units = 1 };
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static slob_t *slobfree = &arena;
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static bigblock_t *bigblocks;
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static DEFINE_SPINLOCK(slob_lock);
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static DEFINE_SPINLOCK(block_lock);
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static void slob_free(void *b, int size);
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static void *slob_alloc(size_t size, gfp_t gfp, int align)
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{
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slob_t *prev, *cur, *aligned = 0;
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int delta = 0, units = SLOB_UNITS(size);
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unsigned long flags;
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spin_lock_irqsave(&slob_lock, flags);
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prev = slobfree;
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for (cur = prev->next; ; prev = cur, cur = cur->next) {
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if (align) {
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aligned = (slob_t *)ALIGN((unsigned long)cur, align);
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delta = aligned - cur;
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}
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if (cur->units >= units + delta) { /* room enough? */
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if (delta) { /* need to fragment head to align? */
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aligned->units = cur->units - delta;
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aligned->next = cur->next;
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cur->next = aligned;
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cur->units = delta;
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prev = cur;
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cur = aligned;
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}
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if (cur->units == units) /* exact fit? */
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prev->next = cur->next; /* unlink */
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else { /* fragment */
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prev->next = cur + units;
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prev->next->units = cur->units - units;
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prev->next->next = cur->next;
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cur->units = units;
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}
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slobfree = prev;
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spin_unlock_irqrestore(&slob_lock, flags);
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return cur;
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}
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if (cur == slobfree) {
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spin_unlock_irqrestore(&slob_lock, flags);
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if (size == PAGE_SIZE) /* trying to shrink arena? */
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return 0;
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cur = (slob_t *)__get_free_page(gfp);
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if (!cur)
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return 0;
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slob_free(cur, PAGE_SIZE);
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spin_lock_irqsave(&slob_lock, flags);
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cur = slobfree;
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}
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}
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}
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static void slob_free(void *block, int size)
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{
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slob_t *cur, *b = (slob_t *)block;
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unsigned long flags;
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if (!block)
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return;
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if (size)
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b->units = SLOB_UNITS(size);
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/* Find reinsertion point */
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spin_lock_irqsave(&slob_lock, flags);
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for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next)
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if (cur >= cur->next && (b > cur || b < cur->next))
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break;
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if (b + b->units == cur->next) {
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b->units += cur->next->units;
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b->next = cur->next->next;
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} else
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b->next = cur->next;
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if (cur + cur->units == b) {
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cur->units += b->units;
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cur->next = b->next;
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} else
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cur->next = b;
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slobfree = cur;
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spin_unlock_irqrestore(&slob_lock, flags);
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}
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static int FASTCALL(find_order(int size));
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static int fastcall find_order(int size)
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{
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int order = 0;
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for ( ; size > 4096 ; size >>=1)
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order++;
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return order;
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}
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void *kmalloc(size_t size, gfp_t gfp)
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{
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slob_t *m;
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bigblock_t *bb;
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unsigned long flags;
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if (size < PAGE_SIZE - SLOB_UNIT) {
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m = slob_alloc(size + SLOB_UNIT, gfp, 0);
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return m ? (void *)(m + 1) : 0;
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}
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bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
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if (!bb)
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return 0;
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bb->order = find_order(size);
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bb->pages = (void *)__get_free_pages(gfp, bb->order);
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if (bb->pages) {
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spin_lock_irqsave(&block_lock, flags);
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bb->next = bigblocks;
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bigblocks = bb;
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spin_unlock_irqrestore(&block_lock, flags);
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return bb->pages;
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}
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slob_free(bb, sizeof(bigblock_t));
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return 0;
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}
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EXPORT_SYMBOL(kmalloc);
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void kfree(const void *block)
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{
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bigblock_t *bb, **last = &bigblocks;
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unsigned long flags;
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if (!block)
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return;
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if (!((unsigned long)block & (PAGE_SIZE-1))) {
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/* might be on the big block list */
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spin_lock_irqsave(&block_lock, flags);
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for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
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if (bb->pages == block) {
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*last = bb->next;
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spin_unlock_irqrestore(&block_lock, flags);
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free_pages((unsigned long)block, bb->order);
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slob_free(bb, sizeof(bigblock_t));
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return;
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}
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}
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spin_unlock_irqrestore(&block_lock, flags);
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}
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slob_free((slob_t *)block - 1, 0);
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return;
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}
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EXPORT_SYMBOL(kfree);
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unsigned int ksize(const void *block)
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{
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bigblock_t *bb;
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unsigned long flags;
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if (!block)
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return 0;
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if (!((unsigned long)block & (PAGE_SIZE-1))) {
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spin_lock_irqsave(&block_lock, flags);
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for (bb = bigblocks; bb; bb = bb->next)
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if (bb->pages == block) {
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spin_unlock_irqrestore(&slob_lock, flags);
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return PAGE_SIZE << bb->order;
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}
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spin_unlock_irqrestore(&block_lock, flags);
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}
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return ((slob_t *)block - 1)->units * SLOB_UNIT;
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}
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struct kmem_cache {
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unsigned int size, align;
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const char *name;
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void (*ctor)(void *, struct kmem_cache *, unsigned long);
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void (*dtor)(void *, struct kmem_cache *, unsigned long);
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};
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struct kmem_cache *kmem_cache_create(const char *name, size_t size,
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size_t align, unsigned long flags,
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void (*ctor)(void*, struct kmem_cache *, unsigned long),
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void (*dtor)(void*, struct kmem_cache *, unsigned long))
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{
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struct kmem_cache *c;
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c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
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if (c) {
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c->name = name;
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c->size = size;
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c->ctor = ctor;
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c->dtor = dtor;
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/* ignore alignment unless it's forced */
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c->align = (flags & SLAB_MUST_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
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if (c->align < align)
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c->align = align;
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}
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return c;
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}
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EXPORT_SYMBOL(kmem_cache_create);
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[PATCH] Make kmem_cache_destroy() return void
un-, de-, -free, -destroy, -exit, etc functions should in general return
void. Also,
There is very little, say, filesystem driver code can do upon failed
kmem_cache_destroy(). If it will be decided to BUG in this case, BUG
should be put in generic code, instead.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-27 02:49:41 -06:00
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void kmem_cache_destroy(struct kmem_cache *c)
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2006-01-08 02:01:45 -07:00
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{
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slob_free(c, sizeof(struct kmem_cache));
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}
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EXPORT_SYMBOL(kmem_cache_destroy);
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void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
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{
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void *b;
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if (c->size < PAGE_SIZE)
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b = slob_alloc(c->size, flags, c->align);
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else
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b = (void *)__get_free_pages(flags, find_order(c->size));
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if (c->ctor)
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c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);
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return b;
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}
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EXPORT_SYMBOL(kmem_cache_alloc);
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2006-03-25 04:06:42 -07:00
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void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
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{
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void *ret = kmem_cache_alloc(c, flags);
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if (ret)
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memset(ret, 0, c->size);
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return ret;
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}
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EXPORT_SYMBOL(kmem_cache_zalloc);
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2006-01-08 02:01:45 -07:00
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void kmem_cache_free(struct kmem_cache *c, void *b)
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{
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if (c->dtor)
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c->dtor(b, c, 0);
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if (c->size < PAGE_SIZE)
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slob_free(b, c->size);
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else
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free_pages((unsigned long)b, find_order(c->size));
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}
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EXPORT_SYMBOL(kmem_cache_free);
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unsigned int kmem_cache_size(struct kmem_cache *c)
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{
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return c->size;
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}
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EXPORT_SYMBOL(kmem_cache_size);
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const char *kmem_cache_name(struct kmem_cache *c)
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{
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return c->name;
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}
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EXPORT_SYMBOL(kmem_cache_name);
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static struct timer_list slob_timer = TIMER_INITIALIZER(
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(void (*)(unsigned long))kmem_cache_init, 0, 0);
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void kmem_cache_init(void)
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{
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void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
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if (p)
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free_page((unsigned long)p);
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mod_timer(&slob_timer, jiffies + HZ);
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}
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