resize2fs: grow uninit_bg file systems more efficiently

If the uninit_bg feature is enabled and the kernel supports
lazy_itable_init, skip zeroing the inode table so that the resize
operation can go much more quickly.  Also set the itable_unused fields
so that the first e2fsck after the resize will run faster.

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

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 85de144..861acff 100644 (file)
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -62,6 +62,8 @@ static errcode_t fix_sb_journal_backup(ext2_filsys fs);
                                 ((blk) < (ext2fs_inode_table_loc((fs), (i)) + \
                                           (fs)->inode_blocks_per_group)))
 
+int lazy_itable_init;
+
 /*
  * This is the top-level routine which does the dirty deed....
  */
@@ -480,6 +482,8 @@ retry:
 
        csum_flag = EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
                                               EXT4_FEATURE_RO_COMPAT_GDT_CSUM);
+       if (access("/sys/fs/ext4/features/lazy_itable_init", F_OK) == 0)
+               lazy_itable_init = 1;
        adj = old_fs->group_desc_count;
        max_group = fs->group_desc_count - adj;
        if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
@@ -494,8 +498,14 @@ retry:
                adjblocks = 0;
 
                ext2fs_bg_flags_zap(fs, i);
-               if (csum_flag)
-                       ext2fs_bg_flags_set(fs, i, EXT2_BG_INODE_UNINIT | EXT2_BG_INODE_ZEROED);
+               if (csum_flag) {
+                       ext2fs_bg_flags_set(fs, i, EXT2_BG_INODE_UNINIT);
+                       if (!lazy_itable_init)
+                               ext2fs_bg_flags_set(fs, i,
+                                                   EXT2_BG_INODE_ZEROED);
+                       ext2fs_bg_itable_unused_set(fs, i,
+                                       fs->super->s_inodes_per_group);
+               }
 
                numblocks = ext2fs_group_blocks_count(fs, i);
                if ((i < fs->group_desc_count - 1) && csum_flag)
@@ -608,7 +618,19 @@ static errcode_t adjust_superblock(ext2_resize_t rfs, blk64_t new_size)
        }
 
        /*
-        * Initialize the new block group descriptors
+        * If we are using uninit_bg (aka GDT_CSUM) and the kernel
+        * supports lazy inode initialization, we can skip
+        * initializing the inode table.
+        */
+       if (lazy_itable_init &&
+           EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+                                      EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+               retval = 0;
+               goto errout;
+       }
+
+       /*
+        * Initialize the inode table
         */
        retval = ext2fs_get_array(fs->blocksize, fs->inode_blocks_per_group,
                                &rfs->itable_buf);