libext2fs: optimize ext2fs_new_block2()

If there are hundreds of thousands of blocks which are in use before
the first free block, it is much, MUCH faster to use
ext2fs_find_first_zero_block_bitmap2() instead of searching the
allocation bitmap bit by bit.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c
index 91637dd..7dcfd3c 100644 (file)
--- a/lib/ext2fs/alloc.c
+++ b/lib/ext2fs/alloc.c
@@ -137,8 +137,8 @@ errcode_t ext2fs_new_inode(ext2_filsys fs, ext2_ino_t dir,
 errcode_t ext2fs_new_block2(ext2_filsys fs, blk64_t goal,
                           ext2fs_block_bitmap map, blk64_t *ret)
 {
-       blk64_t i;
-       int     c_ratio;
+       errcode_t retval;
+       blk64_t b;
 
        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 
@@ -148,21 +148,21 @@ errcode_t ext2fs_new_block2(ext2_filsys fs, blk64_t goal,
                return EXT2_ET_NO_BLOCK_BITMAP;
        if (!goal || (goal >= ext2fs_blocks_count(fs->super)))
                goal = fs->super->s_first_data_block;
-       i = goal;
-       c_ratio = 1 << ext2fs_get_bitmap_granularity(map);
-       if (c_ratio > 1)
-               goal &= ~EXT2FS_CLUSTER_MASK(fs);
-       do {
-               if (!ext2fs_fast_test_block_bitmap2(map, i)) {
-                       clear_block_uninit(fs, ext2fs_group_of_blk2(fs, i));
-                       *ret = i;
-                       return 0;
-               }
-               i = (i + c_ratio) & ~(c_ratio - 1);
-               if (i >= ext2fs_blocks_count(fs->super))
-                       i = fs->super->s_first_data_block;
-       } while (i != goal);
-       return EXT2_ET_BLOCK_ALLOC_FAIL;
+       goal &= ~EXT2FS_CLUSTER_MASK(fs);
+
+       retval = ext2fs_find_first_zero_block_bitmap2(map,
+                       goal, ext2fs_blocks_count(fs->super) - 1, &b);
+       if ((retval == ENOENT) && (goal != fs->super->s_first_data_block))
+               retval = ext2fs_find_first_zero_block_bitmap2(map,
+                       fs->super->s_first_data_block, goal - 1, &b);
+       if (retval == ENOENT)
+               return EXT2_ET_BLOCK_ALLOC_FAIL;
+       if (retval)
+               return retval;
+
+       clear_block_uninit(fs, ext2fs_group_of_blk2(fs, b));
+       *ret = b;
+       return 0;
 }
 
 errcode_t ext2fs_new_block(ext2_filsys fs, blk_t goal,