[PATCH -mm 3/8] Hibernation: Simplify memory bitmap

Rafael J. Wysocki
2008-07-10T00:06:36Z

From: Akinobu Mita <akinobu.mita@gmail.com>
Subject: Hibernation: Simplify memory bitmap

This patch simplifies the memory bitmap manipulations.

- remove the member size in struct bm_block

It is not necessary for struct bm_block to have the number of bit chunks
that can be calculated by using end_pfn and start_pfn.

- use find_next_bit() for memory_bm_next_pfn

No need to invent the bitmap library only for the memory bitmap.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
kernel/power/snapshot.c | 88 +++++++++++-------------------------------------
1 file changed, 21 insertions(+), 67 deletions(-)

Index: linux-next/kernel/power/snapshot.c
===================================================================
--- linux-next.orig/kernel/power/snapshot.c
+++ linux-next/kernel/power/snapshot.c
@@ -205,8 +205,7 @@ static void chain_free(struct chain_allo
* objects. The main list's elements are of type struct zone_bitmap
* and each of them corresonds to one zone. For each zone bitmap
* object there is a list of objects of type struct bm_block that
- * represent each blocks of bit chunks in which information is
- * stored.
+ * represent each blocks of bitmap in which information is stored.
*
* struct memory_bitmap contains a pointer to the main list of zone
* bitmap objects, a struct bm_position used for browsing the bitmap,
@@ -224,26 +223,27 @@ static void chain_free(struct chain_allo
* pfns that correspond to the start and end of the represented zone.
*
* struct bm_block contains a pointer to the memory page in which
- * information is stored (in the form of a block of bit chunks
- * of type unsigned long each). It also contains the pfns that
- * correspond to the start and end of the represented memory area and
- * the number of bit chunks in the block.
+ * information is stored (in the form of a block of bitmap)
+ * It also contains the pfns that correspond to the start and end of
+ * the represented memory area.
*/

#define BM_END_OF_MAP (~0UL)

-#define BM_CHUNKS_PER_BLOCK (PAGE_SIZE / sizeof(long))
-#define BM_BITS_PER_CHUNK (sizeof(long) << 3)
#define BM_BITS_PER_BLOCK (PAGE_SIZE << 3)

struct bm_block {
struct bm_block *next; /* next element of the list */
unsigned long start_pfn; /* pfn represented by the first bit */
unsigned long end_pfn; /* pfn represented by the last bit plus 1 */
- unsigned int size; /* number of bit chunks */
- unsigned long *data; /* chunks of bits representing pages */
+ unsigned long *data; /* bitmap representing pages */
};

+static inline unsigned long bm_block_bits(struct bm_block *bb)
+{
+ return bb->end_pfn - bb->start_pfn;
+}
+
struct zone_bitmap {
struct zone_bitmap *next; /* next element of the list */
unsigned long start_pfn; /* minimal pfn in this zone */
@@ -257,7 +257,6 @@ struct zone_bitmap {
struct bm_position {
struct zone_bitmap *zone_bm;
struct bm_block *block;
- int chunk;
int bit;
};

@@ -272,12 +271,6 @@ struct memory_bitmap {

/* Functions that operate on memory bitmaps */

-static inline void memory_bm_reset_chunk(struct memory_bitmap *bm)
-{
- bm->cur.chunk = 0;
- bm->cur.bit = -1;
-}
-
static void memory_bm_position_reset(struct memory_bitmap *bm)
{
struct zone_bitmap *zone_bm;
@@ -285,7 +278,7 @@ static void memory_bm_position_reset(str
zone_bm = bm->zone_bm_list;
bm->cur.zone_bm = zone_bm;
bm->cur.block = zone_bm->bm_blocks;
- memory_bm_reset_chunk(bm);
+ bm->cur.bit = 0;
}

static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free);
@@ -394,12 +387,10 @@ memory_bm_create(struct memory_bitmap *b
bb->start_pfn = pfn;
if (nr >= BM_BITS_PER_BLOCK) {
pfn += BM_BITS_PER_BLOCK;
- bb->size = BM_CHUNKS_PER_BLOCK;
nr -= BM_BITS_PER_BLOCK;
} else {
/* This is executed only once in the loop */
pfn += nr;
- bb->size = DIV_ROUND_UP(nr, BM_BITS_PER_CHUNK);
}
bb->end_pfn = pfn;
bb = bb->next;
@@ -478,8 +469,8 @@ static int memory_bm_find_bit(struct mem
}
zone_bm->cur_block = bb;
pfn -= bb->start_pfn;
- *bit_nr = pfn % BM_BITS_PER_CHUNK;
- *addr = bb->data + pfn / BM_BITS_PER_CHUNK;
+ *bit_nr = pfn;
+ *addr = bb->data;
return 0;
}

@@ -528,36 +519,6 @@ static int memory_bm_test_bit(struct mem
return test_bit(bit, addr);
}

-/* Two auxiliary functions for memory_bm_next_pfn */
-
-/* Find the first set bit in the given chunk, if there is one */
-
-static inline int next_bit_in_chunk(int bit, unsigned long *chunk_p)
-{
- bit++;
- while (bit < BM_BITS_PER_CHUNK) {
- if (test_bit(bit, chunk_p))
- return bit;
-
- bit++;
- }
- return -1;
-}
-
-/* Find a chunk containing some bits set in given block of bits */
-
-static inline int next_chunk_in_block(int n, struct bm_block *bb)
-{
- n++;
- while (n < bb->size) {
- if (bb->data[n])
- return n;
-
- n++;
- }
- return -1;
-}
-
/**
* memory_bm_next_pfn - find the pfn that corresponds to the next set bit
* in the bitmap @bm. If the pfn cannot be found, BM_END_OF_MAP is
@@ -571,40 +532,33 @@ static unsigned long memory_bm_next_pfn(
{
struct zone_bitmap *zone_bm;
struct bm_block *bb;
- int chunk;
int bit;

do {
bb = bm->cur.block;
do {
- chunk = bm->cur.chunk;
bit = bm->cur.bit;
- do {
- bit = next_bit_in_chunk(bit, bb->data + chunk);
- if (bit >= 0)
- goto Return_pfn;
-
- chunk = next_chunk_in_block(chunk, bb);
- bit = -1;
- } while (chunk >= 0);
+ bit = find_next_bit(bb->data, bm_block_bits(bb), bit);
+ if (bit < bm_block_bits(bb))
+ goto Return_pfn;
+
bb = bb->next;
bm->cur.block = bb;
- memory_bm_reset_chunk(bm);
+ bm->cur.bit = 0;
} while (bb);
zone_bm = bm->cur.zone_bm->next;
if (zone_bm) {
bm->cur.zone_bm = zone_bm;
bm->cur.block = zone_bm->bm_blocks;
- memory_bm_reset_chunk(bm);
+ bm->cur.bit = 0;
}
} while (zone_bm);
memory_bm_position_reset(bm);
return BM_END_OF_MAP;

Return_pfn:
- bm->cur.chunk = chunk;
- bm->cur.bit = bit;
- return bb->start_pfn + chunk * BM_BITS_PER_CHUNK + bit;
+ bm->cur.bit = bit + 1;
+ return bb->start_pfn + bit;
}

/**