[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>

1 files changed, 15 insertions, 20 deletions

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 7fd0576a445..690c42803d2 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);