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ext4: Clean up s_dirt handling

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We don't need to set s_dirt in most of the ext4 code when journaling
is enabled.  In ext3/4 some of the summary statistics for # of free
inodes, blocks, and directories are calculated from the per-block
group statistics when the file system is mounted or unmounted.  As a
result the superblock doesn't have to be updated, either via the
journal or by setting s_dirt.  There are a few exceptions, most
notably when resizing the file system, where the superblock needs to
be modified --- and in that case it should be done as a journalled
operation if possible, and s_dirt set only in no-journal mode.

This patch will optimize out some unneeded disk writes when using ext4
with a journal.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o
2010-06-11 23:14:04 -04:00
parent 7e27d6e778
commit a0375156ca
9 changed files with 36 additions and 16 deletions
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6
fs/ext4/resize.c
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@@ -921,8 +921,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
&sbi->s_flex_groups[flex_group].free_inodes);
}
ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
sb->s_dirt = 1;
ext4_handle_dirty_super(handle, sb);
exit_journal:
mutex_unlock(&sbi->s_resize_lock);
@@ -1045,13 +1044,12 @@ int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
goto exit_put;
}
ext4_blocks_count_set(es, o_blocks_count + add);
ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
sb->s_dirt = 1;
mutex_unlock(&EXT4_SB(sb)->s_resize_lock);
ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,
o_blocks_count + add);
/* We add the blocks to the bitmap and set the group need init bit */
ext4_add_groupblocks(handle, sb, o_blocks_count, add);
ext4_handle_dirty_super(handle, sb);
ext4_debug("freed blocks %llu through %llu\n", o_blocks_count,
o_blocks_count + add);
if ((err = ext4_journal_stop(handle)))