ext4: Fix initalization of s_flex_groups

The s_flex_groups array should have been initialized using atomic_add
to sum up the free counts from the block groups that make up a
flex_bg.  By using atomic_set, the value of the s_flex_groups array
was set to the values of the last block group in the flex_bg.

The impact of this bug is that the block and inode allocation
algorithms might not pick the best flex_bg for new allocation.

Thanks to Damien Guibouret for pointing out this problem!

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

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9f6fa3f..04c6933 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1694,12 +1694,12 @@ static int ext4_fill_flex_info(struct super_block *sb)
                gdp = ext4_get_group_desc(sb, i, NULL);
 
                flex_group = ext4_flex_group(sbi, i);
-               atomic_set(&sbi->s_flex_groups[flex_group].free_inodes,
-                          ext4_free_inodes_count(sb, gdp));
-               atomic_set(&sbi->s_flex_groups[flex_group].free_blocks,
-                          ext4_free_blks_count(sb, gdp));
-               atomic_set(&sbi->s_flex_groups[flex_group].used_dirs,
-                          ext4_used_dirs_count(sb, gdp));
+               atomic_add(ext4_free_inodes_count(sb, gdp),
+                          &sbi->s_flex_groups[flex_group].free_inodes);
+               atomic_add(ext4_free_blks_count(sb, gdp),
+                          &sbi->s_flex_groups[flex_group].free_blocks);
+               atomic_add(ext4_used_dirs_count(sb, gdp),
+                          &sbi->s_flex_groups[flex_group].used_dirs);
        }
 
        return 1;