From 424de6e8e3a2a9681a0f78f7212020c07d6cb3be Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 19 Jan 2014 19:35:33 -0500 Subject: [PATCH] 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" --- lib/ext2fs/alloc.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c index 91637dd4..7dcfd3c3 100644 --- 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,