pm: 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>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 67 deletions

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 5f91a07c4eac..5d2ab836e998 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -205,8 +205,7 @@ static void chain_free(struct chain_allocator *ca, int clear_page_nosave)
  *      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_allocator *ca, int clear_page_nosave)
  *      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(struct memory_bitmap *bm)
         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 *bm, gfp_t gfp_mask, int safe_needed)
                         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 memory_bitmap *bm, unsigned long pfn,
         }
         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 memory_bitmap *bm, unsigned long pfn)
         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 memory_bitmap *bm)
 {
         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;
 }
 
 /**