[PATCH] md/bitmap: use set_bit etc for bitmap page attributes

In particular, this means that we use 4 bits per page instead of a whole
unsigned long.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 7 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 0f1732570770..2e257d5998bc 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -700,27 +700,27 @@ static void bitmap_file_kick(struct bitmap *bitmap)
 }
 
 enum bitmap_page_attr {
-        BITMAP_PAGE_DIRTY = 1, // there are set bits that need to be synced
-        BITMAP_PAGE_CLEAN = 2, // there are bits that might need to be cleared
-        BITMAP_PAGE_NEEDWRITE=4, // there are cleared bits that need to be synced
+        BITMAP_PAGE_DIRTY = 0, // there are set bits that need to be synced
+        BITMAP_PAGE_CLEAN = 1, // there are bits that might need to be cleared
+        BITMAP_PAGE_NEEDWRITE=2, // there are cleared bits that need to be synced
 };
 
 static inline void set_page_attr(struct bitmap *bitmap, struct page *page,
                                 enum bitmap_page_attr attr)
 {
-        bitmap->filemap_attr[page->index] |= attr;
+        __set_bit((page->index<<2) + attr, bitmap->filemap_attr);
 }
 
 static inline void clear_page_attr(struct bitmap *bitmap, struct page *page,
                                 enum bitmap_page_attr attr)
 {
-        bitmap->filemap_attr[page->index] &= ~attr;
+        __clear_bit((page->index<<2) + attr, bitmap->filemap_attr);
 }
 
 static inline unsigned long test_page_attr(struct bitmap *bitmap, struct page *page,
                                            enum bitmap_page_attr attr)
 {
-        return bitmap->filemap_attr[page->index] & attr;
+        return test_bit((page->index<<2) + attr, bitmap->filemap_attr);
 }
 
 /*
@@ -872,7 +872,12 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
         if (!bitmap->filemap)
                 goto out;
 
-        bitmap->filemap_attr = kzalloc(sizeof(long) * num_pages, GFP_KERNEL);
+        /* We need 4 bits per page, rounded up to a multiple of sizeof(unsigned long) */
+        bitmap->filemap_attr = kzalloc(
+                (((num_pages*4/8)+sizeof(unsigned long)-1)
+                 /sizeof(unsigned long))
+                *sizeof(unsigned long),
+                GFP_KERNEL);
         if (!bitmap->filemap_attr)
                 goto out;