[PATCH] change gen_pool allocator to not touch managed memory

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>

4 files changed, 252 insertions, 261 deletions

diff --git a/arch/ia64/kernel/uncached.c b/arch/ia64/kernel/uncached.c
index fcd2bad0286f..5f03b9e524dd 100644
--- a/arch/ia64/kernel/uncached.c
+++ b/arch/ia64/kernel/uncached.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2001-2005 Silicon Graphics, Inc.  All rights reserved.
+ * Copyright (C) 2001-2006 Silicon Graphics, Inc.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of version 2 of the GNU General Public License
@@ -29,15 +29,8 @@
 #include <asm/tlbflush.h>
 #include <asm/sn/arch.h>
 
-#define DEBUG   0
 
-#if DEBUG
-#define dprintk                 printk
-#else
-#define dprintk(x...)           do { } while (0)
-#endif
-
-void __init efi_memmap_walk_uc (efi_freemem_callback_t callback);
+extern void __init efi_memmap_walk_uc(efi_freemem_callback_t, void *);
 
 #define MAX_UNCACHED_GRANULES   5
 static int allocated_granules;
@@ -60,6 +53,7 @@ static void uncached_ipi_visibility(void *data)
 static void uncached_ipi_mc_drain(void *data)
 {
         int status;
+
         status = ia64_pal_mc_drain();
         if (status)
                 printk(KERN_WARNING "ia64_pal_mc_drain() failed with %i on "
@@ -67,30 +61,35 @@ static void uncached_ipi_mc_drain(void *data)
 }
 
 
-static unsigned long
-uncached_get_new_chunk(struct gen_pool *poolp)
+/*
+ * Add a new chunk of uncached memory pages to the specified pool.
+ *
+ * @pool: pool to add new chunk of uncached memory to
+ * @nid: node id of node to allocate memory from, or -1
+ *
+ * This is accomplished by first allocating a granule of cached memory pages
+ * and then converting them to uncached memory pages.
+ */
+static int uncached_add_chunk(struct gen_pool *pool, int nid)
 {
         struct page *page;
-        void *tmp;
         int status, i;
-        unsigned long addr, node;
+        unsigned long c_addr, uc_addr;
 
         if (allocated_granules >= MAX_UNCACHED_GRANULES)
-                return 0;
+                return -1;
+
+        /* attempt to allocate a granule's worth of cached memory pages */
 
-        node = poolp->private;
-        page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO,
+        page = alloc_pages_node(nid, GFP_KERNEL | __GFP_ZERO,
                                 IA64_GRANULE_SHIFT-PAGE_SHIFT);
+        if (!page)
+                return -1;
 
-        dprintk(KERN_INFO "get_new_chunk page %p, addr %lx\n",
-                page, (unsigned long)(page-vmem_map) << PAGE_SHIFT);
+        /* convert the memory pages from cached to uncached */
 
-        /*
-         * Do magic if no mem on local node! XXX
-         */
-        if (!page)
-                return 0;
-        tmp = page_address(page);
+        c_addr = (unsigned long)page_address(page);
+        uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
 
         /*
          * There's a small race here where it's possible for someone to
@@ -100,76 +99,90 @@ uncached_get_new_chunk(struct gen_pool *poolp)
         for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
                 SetPageUncached(&page[i]);
 
-        flush_tlb_kernel_range(tmp, tmp + IA64_GRANULE_SIZE);
+        flush_tlb_kernel_range(uc_addr, uc_adddr + IA64_GRANULE_SIZE);
 
         status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
-
-        dprintk(KERN_INFO "pal_prefetch_visibility() returns %i on cpu %i\n",
-                status, raw_smp_processor_id());
-
         if (!status) {
                 status = smp_call_function(uncached_ipi_visibility, NULL, 0, 1);
                 if (status)
-                        printk(KERN_WARNING "smp_call_function failed for "
-                               "uncached_ipi_visibility! (%i)\n", status);
+                        goto failed;
         }
 
+        preempt_disable();
+
         if (ia64_platform_is("sn2"))
-                sn_flush_all_caches((unsigned long)tmp, IA64_GRANULE_SIZE);
+                sn_flush_all_caches(uc_addr, IA64_GRANULE_SIZE);
         else
-                flush_icache_range((unsigned long)tmp,
-                                   (unsigned long)tmp+IA64_GRANULE_SIZE);
+                flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);
+
+        /* flush the just introduced uncached translation from the TLB */
+        local_flush_tlb_all();
+
+        preempt_enable();
 
         ia64_pal_mc_drain();
         status = smp_call_function(uncached_ipi_mc_drain, NULL, 0, 1);
         if (status)
-                printk(KERN_WARNING "smp_call_function failed for "
-                       "uncached_ipi_mc_drain! (%i)\n", status);
+                goto failed;
 
-        addr = (unsigned long)tmp - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
+        /*
+         * The chunk of memory pages has been converted to uncached so now we
+         * can add it to the pool.
+         */
+        status = gen_pool_add(pool, uc_addr, IA64_GRANULE_SIZE, nid);
+        if (status)
+                goto failed;
 
         allocated_granules++;
-        return addr;
+        return 0;
+
+        /* failed to convert or add the chunk so give it back to the kernel */
+failed:
+        for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
+                ClearPageUncached(&page[i]);
+
+        free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
+        return -1;
 }
 
 
 /*
  * uncached_alloc_page
  *
+ * @starting_nid: node id of node to start with, or -1
+ *
  * Allocate 1 uncached page. Allocates on the requested node. If no
  * uncached pages are available on the requested node, roundrobin starting
- * with higher nodes.
+ * with the next higher node.
  */
-unsigned long
-uncached_alloc_page(int nid)
+unsigned long uncached_alloc_page(int starting_nid)
 {
-        unsigned long maddr;
+        unsigned long uc_addr;
+        struct gen_pool *pool;
+        int nid;
 
-        maddr = gen_pool_alloc(uncached_pool[nid], PAGE_SIZE);
+        if (unlikely(starting_nid >= MAX_NUMNODES))
+                return 0;
 
-        dprintk(KERN_DEBUG "uncached_alloc_page returns %lx on node %i\n",
-                maddr, nid);
+        if (starting_nid < 0)
+                starting_nid = numa_node_id();
+        nid = starting_nid;
 
-        /*
-         * If no memory is availble on our local node, try the
-         * remaining nodes in the system.
-         */
-        if (!maddr) {
-                int i;
-
-                for (i = MAX_NUMNODES - 1; i >= 0; i--) {
-                        if (i == nid || !node_online(i))
-                                continue;
-                        maddr = gen_pool_alloc(uncached_pool[i], PAGE_SIZE);
-                        dprintk(KERN_DEBUG "uncached_alloc_page alternate search "
-                                "returns %lx on node %i\n", maddr, i);
-                        if (maddr) {
-                                break;
-                        }
-                }
-        }
+        do {
+                if (!node_online(nid))
+                        continue;
+                pool = uncached_pool[nid];
+                if (pool == NULL)
+                        continue;
+                do {
+                        uc_addr = gen_pool_alloc(pool, PAGE_SIZE);
+                        if (uc_addr != 0)
+                                return uc_addr;
+                } while (uncached_add_chunk(pool, nid) == 0);
+
+        } while ((nid = (nid + 1) % MAX_NUMNODES) != starting_nid);
 
-        return maddr;
+        return 0;
 }
 EXPORT_SYMBOL(uncached_alloc_page);
 
@@ -177,21 +190,22 @@ EXPORT_SYMBOL(uncached_alloc_page);
 /*
  * uncached_free_page
  *
+ * @uc_addr: uncached address of page to free
+ *
  * Free a single uncached page.
  */
-void
-uncached_free_page(unsigned long maddr)
+void uncached_free_page(unsigned long uc_addr)
 {
-        int node;
-
-        node = paddr_to_nid(maddr - __IA64_UNCACHED_OFFSET);
+        int nid = paddr_to_nid(uc_addr - __IA64_UNCACHED_OFFSET);
+        struct gen_pool *pool = uncached_pool[nid];
 
-        dprintk(KERN_DEBUG "uncached_free_page(%lx) on node %i\n", maddr, node);
+        if (unlikely(pool == NULL))
+                return;
 
-        if ((maddr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
-                panic("uncached_free_page invalid address %lx\n", maddr);
+        if ((uc_addr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
+                panic("uncached_free_page invalid address %lx\n", uc_addr);
 
-        gen_pool_free(uncached_pool[node], maddr, PAGE_SIZE);
+        gen_pool_free(pool, uc_addr, PAGE_SIZE);
 }
 EXPORT_SYMBOL(uncached_free_page);
 
@@ -199,43 +213,39 @@ EXPORT_SYMBOL(uncached_free_page);
 /*
  * uncached_build_memmap,
  *
+ * @uc_start: uncached starting address of a chunk of uncached memory
+ * @uc_end: uncached ending address of a chunk of uncached memory
+ * @arg: ignored, (NULL argument passed in on call to efi_memmap_walk_uc())
+ *
  * Called at boot time to build a map of pages that can be used for
  * memory special operations.
  */
-static int __init
-uncached_build_memmap(unsigned long start, unsigned long end, void *arg)
+static int __init uncached_build_memmap(unsigned long uc_start,
+                                        unsigned long uc_end, void *arg)
 {
-        long length = end - start;
-        int node;
-
-        dprintk(KERN_ERR "uncached_build_memmap(%lx %lx)\n", start, end);
+        int nid = paddr_to_nid(uc_start - __IA64_UNCACHED_OFFSET);
+        struct gen_pool *pool = uncached_pool[nid];
+        size_t size = uc_end - uc_start;
 
         touch_softlockup_watchdog();
-        memset((char *)start, 0, length);
 
-        node = paddr_to_nid(start - __IA64_UNCACHED_OFFSET);
-
-        for (; start < end ; start += PAGE_SIZE) {
-                dprintk(KERN_INFO "sticking %lx into the pool!\n", start);
-                gen_pool_free(uncached_pool[node], start, PAGE_SIZE);
+        if (pool != NULL) {
+                memset((char *)uc_start, 0, size);
+                (void) gen_pool_add(pool, uc_start, size, nid);
         }
-
         return 0;
 }
 
 
-static int __init uncached_init(void) {
-        int i;
+static int __init uncached_init(void)
+{
+        int nid;
 
-        for (i = 0; i < MAX_NUMNODES; i++) {
-                if (!node_online(i))
-                        continue;
-                uncached_pool[i] = gen_pool_create(0, IA64_GRANULE_SHIFT,
-                                                   &uncached_get_new_chunk, i);
+        for_each_online_node(nid) {
+                uncached_pool[nid] = gen_pool_create(PAGE_SHIFT, nid);
         }
 
-        efi_memmap_walk_uc(uncached_build_memmap);
-
+        efi_memmap_walk_uc(uncached_build_memmap, NULL);
         return 0;
 }
 
diff --git a/arch/ia64/sn/kernel/sn2/cache.c b/arch/ia64/sn/kernel/sn2/cache.c
index bc3cfa17cd0f..2862cb33026d 100644
--- a/arch/ia64/sn/kernel/sn2/cache.c
+++ b/arch/ia64/sn/kernel/sn2/cache.c
@@ -3,11 +3,12 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  * 
- * Copyright (C) 2001-2003 Silicon Graphics, Inc. All rights reserved.
+ * Copyright (C) 2001-2003, 2006 Silicon Graphics, Inc. All rights reserved.
  *
  */
 #include <linux/module.h>
 #include <asm/pgalloc.h>
+#include <asm/sn/arch.h>
 
 /**
  * sn_flush_all_caches - flush a range of address from all caches (incl. L4)
@@ -17,18 +18,24 @@
  * Flush a range of addresses from all caches including L4. 
  * All addresses fully or partially contained within 
  * @flush_addr to @flush_addr + @bytes are flushed
- * from the all caches.
+ * from all caches.
  */
 void
 sn_flush_all_caches(long flush_addr, long bytes)
 {
-        flush_icache_range(flush_addr, flush_addr+bytes);
+        unsigned long addr = flush_addr;
+
+        /* SHub1 requires a cached address */
+        if (is_shub1() && (addr & RGN_BITS) == RGN_BASE(RGN_UNCACHED))
+                addr = (addr - RGN_BASE(RGN_UNCACHED)) + RGN_BASE(RGN_KERNEL);
+
+        flush_icache_range(addr, addr + bytes);
         /*
          * The last call may have returned before the caches
          * were actually flushed, so we call it again to make
          * sure.
          */
-        flush_icache_range(flush_addr, flush_addr+bytes);
+        flush_icache_range(addr, addr + bytes);
         mb();
 }
 EXPORT_SYMBOL(sn_flush_all_caches);
diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 7fd0576a4454..690c42803d2e 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -4,37 +4,32 @@
  * 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, adapted for general purpose use.
- *
  * This source code is licensed under the GNU General Public License,
  * Version 2.  See the file COPYING for more details.
  */
 
-#include <linux/spinlock.h>
 
-#define ALLOC_MIN_SHIFT         5 /* 32 bytes minimum */
 /*
- *  Link between free memory chunks of a given size.
+ *  General purpose special memory pool descriptor.
  */
-struct gen_pool_link {
-        struct gen_pool_link *next;
+struct gen_pool {
+        rwlock_t lock;
+        struct list_head chunks;        /* list of chunks in this pool */
+        int min_alloc_order;            /* minimum allocation order */
 };
 
 /*
- *  Memory pool descriptor.
+ *  General purpose special memory pool chunk descriptor.
  */
-struct gen_pool {
+struct gen_pool_chunk {
         spinlock_t lock;
-        unsigned long (*get_new_chunk)(struct gen_pool *);
-        struct gen_pool *next;
-        struct gen_pool_link *h;
-        unsigned long private;
-        int max_chunk_shift;
+        struct list_head next_chunk;    /* next chunk in pool */
+        unsigned long start_addr;       /* starting address of memory chunk */
+        unsigned long end_addr;         /* ending address of memory chunk */
+        unsigned long bits[0];          /* bitmap for allocating memory chunk */
 };
 
-unsigned long gen_pool_alloc(struct gen_pool *poolp, int size);
-void gen_pool_free(struct gen_pool *mp, unsigned long ptr, int size);
-struct gen_pool *gen_pool_create(int nr_chunks, int max_chunk_shift,
-                                 unsigned long (*fp)(struct gen_pool *),
-                                 unsigned long data);
+extern struct gen_pool *gen_pool_create(int, int);
+extern int gen_pool_add(struct gen_pool *, unsigned long, size_t, int);
+extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
+extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 9ce0a6a3b85a..71338b48e889 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -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;
-
-        /*
-         * 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;
-        }
-        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));
-        }
+        struct gen_pool *pool;
 
-        return poolp;
+        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;
+        }
+        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)
-                return 0;
+        memset(chunk, 0, nbytes);
+        spin_lock_init(&chunk->lock);
+        chunk->start_addr = addr;
+        chunk->end_addr = addr + size;
 
-        size = max(size, 1 << ALLOC_MIN_SHIFT);
-        i = fls(size - 1);
-        s = 1 << i;
-        j = i -= ALLOC_MIN_SHIFT;
-
-        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;
-                }
-                j++;
-                s <<= 1;
-        }
-        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;
+        write_lock(&pool->lock);
+        list_add(&chunk->next_chunk, &pool->chunks);
+        write_unlock(&pool->lock);
+
+        return 0;
 }
-EXPORT_SYMBOL(gen_pool_alloc);
+EXPORT_SYMBOL(gen_pool_add);
 
 
 /*
- *  Counter-part of the generic allocator.
+ * 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
  */
-void gen_pool_free(struct gen_pool *poolp, unsigned long ptr, int size)
+unsigned long gen_pool_alloc(struct gen_pool *pool, 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;
-
-        max_chunk_size = 1 << poolp->max_chunk_shift;
+        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 > max_chunk_size)
-                return;
-
-        size = max(size, 1 << ALLOC_MIN_SHIFT);
-        i = fls(size - 1);
-        s = 1 << i;
-        i -= ALLOC_MIN_SHIFT;
-
-        a = ptr;
+        if (size == 0)
+                return 0;
 
-        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;
-                        break;
+        nbits = (size + (1UL << order) - 1) >> order;
+
+        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;
                 }
-                b = a ^ s;
-                q = &h[i];
+                spin_unlock_irqrestore(&chunk->lock, flags);
+        }
+        read_unlock(&pool->lock);
+        return 0;
+}
+EXPORT_SYMBOL(gen_pool_alloc);
 
-                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;
+/*
+ * 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 *pool, unsigned long addr, size_t size)
+{
+        struct list_head *_chunk;
+        struct gen_pool_chunk *chunk;
+        unsigned long flags;
+        int order = pool->min_alloc_order;
+        int bit, nbits;
+
+        nbits = (size + (1UL << order) - 1) >> order;
+
+        read_lock(&pool->lock);
+        list_for_each(_chunk, &pool->chunks) {
+                chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
+
+                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;
                 }
-                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);