Further optimize journal placement for flex_bg filesystems

If the number of block groups is greater than half the flex_bg size,
the journal we be placed in the flex_bg super-group which is closest
to the mid-point of the filesystem, and in the first free block group
beyond where the metadata for the flex_bg is stored.

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

diff --git a/lib/ext2fs/mkjournal.c b/lib/ext2fs/mkjournal.c
index 96b574e..f5a9dba 100644 (file)
--- a/lib/ext2fs/mkjournal.c
+++ b/lib/ext2fs/mkjournal.c
@@ -275,7 +275,7 @@ static errcode_t write_journal_inode(ext2_filsys fs, ext2_ino_t journal_ino,
                                     blk_t size, int flags)
 {
        char                    *buf;
-       dgrp_t                  group, start, end, i;
+       dgrp_t                  group, start, end, i, log_flex;
        errcode_t               retval;
        struct ext2_inode       inode;
        struct mkjournal_struct es;
@@ -311,7 +311,17 @@ static errcode_t write_journal_inode(ext2_filsys fs, ext2_ino_t journal_ino,
         */
        group = ext2fs_group_of_blk(fs, (fs->super->s_blocks_count -
                                         fs->super->s_first_data_block) / 2);
-       start = (group > 0) ? group-1 : group;
+       log_flex = 1 << fs->super->s_log_groups_per_flex;
+       if (fs->super->s_log_groups_per_flex && (group > log_flex)) {
+               group = group & ~(log_flex - 1);
+               while ((group < fs->group_desc_count) &&
+                      fs->group_desc[group].bg_free_blocks_count == 0)
+                       group++;
+               if (group == fs->group_desc_count)
+                       group = 0;
+               start = group;
+       } else
+               start = (group > 0) ? group-1 : group;
        end = ((group+1) < fs->group_desc_count) ? group+1 : group;
        group = start;
        for (i=start+1; i <= end; i++)