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[PATCH] change gen_pool allocator to not touch managed memory

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Modify the gen_pool allocator (lib/genalloc.c) to utilize a bitmap scheme
instead of the buddy scheme.  The purpose of this change is to eliminate
the touching of the actual memory being allocated.

Since the change modifies the interface, a change to the uncached allocator
(arch/ia64/kernel/uncached.c) is also required.

Both Andrey Volkov and Jes Sorenson have expressed a desire that the
gen_pool allocator not write to the memory being managed. See the
following:

  http://marc.theaimsgroup.com/?l=linux-kernel&m=113518602713125&w=2
  http://marc.theaimsgroup.com/?l=linux-kernel&m=113533568827916&w=2

Signed-off-by: Dean Nelson <dcn@sgi.com>
Cc: Andrey Volkov <avolkov@varma-el.com>
Acked-by: Jes Sorensen <jes@trained-monkey.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Dean Nelson 2006-06-23 02:03:21 -07:00 • committed by Linus Torvalds
parent 833423143c
commit 929f97276b
4 changed files with 252 additions and 261 deletions
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255
lib/genalloc.c
View file

@ -4,10 +4,6 @@
* Uses for this includes on-device special memory, uncached memory
* etc.
*
* This code is based on the buddy allocator found in the sym53c8xx_2
* driver Copyright (C) 1999-2001 Gerard Roudier <groudier@free.fr>,
* and adapted for general purpose use.
*
* Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
*
* This source code is licensed under the GNU General Public License,
@ -15,172 +11,155 @@
*/
#include <linux/module.h>
#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/genalloc.h>
#include <asm/page.h>
struct gen_pool *gen_pool_create(int nr_chunks, int max_chunk_shift,
unsigned long (*fp)(struct gen_pool *),
unsigned long data)
/*
* Create a new special memory pool.
*
* @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
* @nid: node id of the node the pool structure should be allocated on, or -1
*/
struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
{
struct gen_pool *poolp;
unsigned long tmp;
int i;
struct gen_pool *pool;
/*
* This is really an arbitrary limit, +10 is enough for
* IA64_GRANULE_SHIFT, aka 16MB. If anyone needs a large limit
* this can be increased without problems.
*/
if ((max_chunk_shift > (PAGE_SHIFT + 10)) ||
((max_chunk_shift < ALLOC_MIN_SHIFT) && max_chunk_shift))
return NULL;
if (!max_chunk_shift)
max_chunk_shift = PAGE_SHIFT;
poolp = kmalloc(sizeof(struct gen_pool), GFP_KERNEL);
if (!poolp)
return NULL;
memset(poolp, 0, sizeof(struct gen_pool));
poolp->h = kmalloc(sizeof(struct gen_pool_link) *
(max_chunk_shift - ALLOC_MIN_SHIFT + 1),
GFP_KERNEL);
if (!poolp->h) {
printk(KERN_WARNING "gen_pool_alloc() failed to allocate\n");
kfree(poolp);
return NULL;
pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
if (pool != NULL) {
rwlock_init(&pool->lock);
INIT_LIST_HEAD(&pool->chunks);
pool->min_alloc_order = min_alloc_order;
}
memset(poolp->h, 0, sizeof(struct gen_pool_link) *
(max_chunk_shift - ALLOC_MIN_SHIFT + 1));
spin_lock_init(&poolp->lock);
poolp->get_new_chunk = fp;
poolp->max_chunk_shift = max_chunk_shift;
poolp->private = data;
for (i = 0; i < nr_chunks; i++) {
tmp = poolp->get_new_chunk(poolp);
printk(KERN_INFO "allocated %lx\n", tmp);
if (!tmp)
break;
gen_pool_free(poolp, tmp, (1 << poolp->max_chunk_shift));
}
return poolp;
return pool;
}
EXPORT_SYMBOL(gen_pool_create);
/*
* Simple power of two buddy-like generic allocator.
* Provides naturally aligned memory chunks.
* Add a new chunk of memory to the specified pool.
*
* @pool: pool to add new memory chunk to
* @addr: starting address of memory chunk to add to pool
* @size: size in bytes of the memory chunk to add to pool
* @nid: node id of the node the chunk structure and bitmap should be
* allocated on, or -1
*/
unsigned long gen_pool_alloc(struct gen_pool *poolp, int size)
int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
int nid)
{
int j, i, s, max_chunk_size;
unsigned long a, flags;
struct gen_pool_link *h = poolp->h;
struct gen_pool_chunk *chunk;
int nbits = size >> pool->min_alloc_order;
int nbytes = sizeof(struct gen_pool_chunk) +
(nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
max_chunk_size = 1 << poolp->max_chunk_shift;
chunk = kmalloc_node(nbytes, GFP_KERNEL, nid);
if (unlikely(chunk == NULL))
return -1;
if (size > max_chunk_size)
memset(chunk, 0, nbytes);
spin_lock_init(&chunk->lock);
chunk->start_addr = addr;
chunk->end_addr = addr + size;
write_lock(&pool->lock);
list_add(&chunk->next_chunk, &pool->chunks);
write_unlock(&pool->lock);
return 0;
}
EXPORT_SYMBOL(gen_pool_add);
/*
* Allocate the requested number of bytes from the specified pool.
* Uses a first-fit algorithm.
*
* @pool: pool to allocate from
* @size: number of bytes to allocate from the pool
*/
unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
{
struct list_head *_chunk;
struct gen_pool_chunk *chunk;
unsigned long addr, flags;
int order = pool->min_alloc_order;
int nbits, bit, start_bit, end_bit;
if (size == 0)
return 0;
size = max(size, 1 << ALLOC_MIN_SHIFT);
i = fls(size - 1);
s = 1 << i;
j = i -= ALLOC_MIN_SHIFT;
nbits = (size + (1UL << order) - 1) >> order;
spin_lock_irqsave(&poolp->lock, flags);
while (!h[j].next) {
if (s == max_chunk_size) {
struct gen_pool_link *ptr;
spin_unlock_irqrestore(&poolp->lock, flags);
ptr = (struct gen_pool_link *)poolp->get_new_chunk(poolp);
spin_lock_irqsave(&poolp->lock, flags);
h[j].next = ptr;
if (h[j].next)
h[j].next->next = NULL;
break;
read_lock(&pool->lock);
list_for_each(_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
end_bit = (chunk->end_addr - chunk->start_addr) >> order;
end_bit -= nbits + 1;
spin_lock_irqsave(&chunk->lock, flags);
bit = -1;
while (bit + 1 < end_bit) {
bit = find_next_zero_bit(chunk->bits, end_bit, bit + 1);
if (bit >= end_bit)
break;
start_bit = bit;
if (nbits > 1) {
bit = find_next_bit(chunk->bits, bit + nbits,
bit + 1);
if (bit - start_bit < nbits)
continue;
}
addr = chunk->start_addr +
((unsigned long)start_bit << order);
while (nbits--)
__set_bit(start_bit++, &chunk->bits);
spin_unlock_irqrestore(&chunk->lock, flags);
read_unlock(&pool->lock);
return addr;
}
j++;
s <<= 1;
spin_unlock_irqrestore(&chunk->lock, flags);
}
a = (unsigned long) h[j].next;
if (a) {
h[j].next = h[j].next->next;
/*
* This should be split into a seperate function doing
* the chunk split in order to support custom
* handling memory not physically accessible by host
*/
while (j > i) {
j -= 1;
s >>= 1;
h[j].next = (struct gen_pool_link *) (a + s);
h[j].next->next = NULL;
}
}
spin_unlock_irqrestore(&poolp->lock, flags);
return a;
read_unlock(&pool->lock);
return 0;
}
EXPORT_SYMBOL(gen_pool_alloc);
/*
* Counter-part of the generic allocator.
* Free the specified memory back to the specified pool.
*
* @pool: pool to free to
* @addr: starting address of memory to free back to pool
* @size: size in bytes of memory to free
*/
void gen_pool_free(struct gen_pool *poolp, unsigned long ptr, int size)
void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
{
struct gen_pool_link *q;
struct gen_pool_link *h = poolp->h;
unsigned long a, b, flags;
int i, s, max_chunk_size;
struct list_head *_chunk;
struct gen_pool_chunk *chunk;
unsigned long flags;
int order = pool->min_alloc_order;
int bit, nbits;
max_chunk_size = 1 << poolp->max_chunk_shift;
nbits = (size + (1UL << order) - 1) >> order;
if (size > max_chunk_size)
return;
read_lock(&pool->lock);
list_for_each(_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
size = max(size, 1 << ALLOC_MIN_SHIFT);
i = fls(size - 1);
s = 1 << i;
i -= ALLOC_MIN_SHIFT;
a = ptr;
spin_lock_irqsave(&poolp->lock, flags);
while (1) {
if (s == max_chunk_size) {
((struct gen_pool_link *)a)->next = h[i].next;
h[i].next = (struct gen_pool_link *)a;
if (addr >= chunk->start_addr && addr < chunk->end_addr) {
BUG_ON(addr + size > chunk->end_addr);
spin_lock_irqsave(&chunk->lock, flags);
bit = (addr - chunk->start_addr) >> order;
while (nbits--)
__clear_bit(bit++, &chunk->bits);
spin_unlock_irqrestore(&chunk->lock, flags);
break;
}
b = a ^ s;
q = &h[i];
while (q->next && q->next != (struct gen_pool_link *)b)
q = q->next;
if (!q->next) {
((struct gen_pool_link *)a)->next = h[i].next;
h[i].next = (struct gen_pool_link *)a;
break;
}
q->next = q->next->next;
a = a & b;
s <<= 1;
i++;
}
spin_unlock_irqrestore(&poolp->lock, flags);
BUG_ON(nbits > 0);
read_unlock(&pool->lock);
}
EXPORT_SYMBOL(gen_pool_free);