resize2fs: optimize resize2fs_calculate_summary_stats()

Speed up an off-line resize of a 10GB file system to 64TB located on
tmpfs from 90 seconds to 16 seconds by extracting block group bitmaps
using a population count function to count the blocks in use instead
checking each bit in the block bitmap.

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

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 5ed0c9e..73174be 100644 (file)
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -2844,69 +2844,40 @@ errout:
  */
 static errcode_t resize2fs_calculate_summary_stats(ext2_filsys fs)
 {
-       blk64_t         blk;
+       errcode_t       retval;
+       blk64_t         blk = fs->super->s_first_data_block;
        ext2_ino_t      ino;
-       unsigned int    group = 0;
-       unsigned int    count = 0;
-       blk64_t         total_blocks_free = 0;
+       unsigned int    n, c, group, count;
+       blk64_t         total_clusters_free = 0;
        int             total_inodes_free = 0;
        int             group_free = 0;
        int             uninit = 0;
-       blk64_t         super_blk, old_desc_blk, new_desc_blk;
-       int             old_desc_blocks;
+       char            *bitmap_buf;
 
        /*
         * First calculate the block statistics
         */
-       uninit = ext2fs_bg_flags_test(fs, group, EXT2_BG_BLOCK_UNINIT);
-       ext2fs_super_and_bgd_loc2(fs, group, &super_blk, &old_desc_blk,
-                                 &new_desc_blk, 0);
-       if (ext2fs_has_feature_meta_bg(fs->super))
-               old_desc_blocks = fs->super->s_first_meta_bg;
-       else
-               old_desc_blocks = fs->desc_blocks +
-                       fs->super->s_reserved_gdt_blocks;
-       for (blk = B2C(fs->super->s_first_data_block);
-            blk < ext2fs_blocks_count(fs->super);
-            blk += EXT2FS_CLUSTER_RATIO(fs)) {
-               if ((uninit &&
-                    !(EQ_CLSTR(blk, super_blk) ||
-                      ((old_desc_blk && old_desc_blocks &&
-                        GE_CLSTR(blk, old_desc_blk) &&
-                        LT_CLSTR(blk, old_desc_blk + old_desc_blocks))) ||
-                      ((new_desc_blk && EQ_CLSTR(blk, new_desc_blk))) ||
-                      EQ_CLSTR(blk, ext2fs_block_bitmap_loc(fs, group)) ||
-                      EQ_CLSTR(blk, ext2fs_inode_bitmap_loc(fs, group)) ||
-                      ((GE_CLSTR(blk, ext2fs_inode_table_loc(fs, group)) &&
-                        LT_CLSTR(blk, ext2fs_inode_table_loc(fs, group)
-                                 + fs->inode_blocks_per_group))))) ||
-                   (!ext2fs_fast_test_block_bitmap2(fs->block_map, blk))) {
-                       group_free++;
-                       total_blocks_free++;
-               }
-               count++;
-               if ((count == fs->super->s_clusters_per_group) ||
-                   EQ_CLSTR(blk, ext2fs_blocks_count(fs->super)-1)) {
-                       ext2fs_bg_free_blocks_count_set(fs, group, group_free);
-                       ext2fs_group_desc_csum_set(fs, group);
-                       group++;
-                       if (group >= fs->group_desc_count)
-                               break;
-                       count = 0;
-                       group_free = 0;
-                       uninit = ext2fs_bg_flags_test(fs, group, EXT2_BG_BLOCK_UNINIT);
-                       ext2fs_super_and_bgd_loc2(fs, group, &super_blk,
-                                                 &old_desc_blk,
-                                                 &new_desc_blk, 0);
-                       if (ext2fs_has_feature_meta_bg(fs->super))
-                               old_desc_blocks = fs->super->s_first_meta_bg;
-                       else
-                               old_desc_blocks = fs->desc_blocks +
-                                       fs->super->s_reserved_gdt_blocks;
+       bitmap_buf = malloc(fs->blocksize);
+       if (!bitmap_buf)
+               return ENOMEM;
+       for (group = 0; group < fs->group_desc_count;
+            group++) {
+               retval = ext2fs_get_block_bitmap_range2(fs->block_map,
+                       B2C(blk), fs->super->s_clusters_per_group, bitmap_buf);
+               if (retval) {
+                       free(bitmap_buf);
+                       return retval;
                }
-       }
-       total_blocks_free = C2B(total_blocks_free);
-       ext2fs_free_blocks_count_set(fs->super, total_blocks_free);
+               n = ext2fs_bitcount(bitmap_buf,
+                                   fs->super->s_clusters_per_group / 8);
+               group_free = fs->super->s_clusters_per_group - n;
+               total_clusters_free += group_free;
+               ext2fs_bg_free_blocks_count_set(fs, group, group_free);
+               ext2fs_group_desc_csum_set(fs, group);
+               blk += fs->super->s_blocks_per_group;
+       }
+       free(bitmap_buf);
+       ext2fs_free_blocks_count_set(fs->super, C2B(total_clusters_free));
 
        /*
         * Next, calculate the inode statistics