https://bugzilla.kernel.org/show_bug.cgi?id=13549
--- Comment #18 from Eric Sandeen <[email protected]> 2010-03-27 19:16:09 ---
Reproducer works perfectly, thanks.
So here's the issue; sbi->flex_groups[] doesn't get filled out in
ext4_fill_flex_info() because:
if (groups_per_flex < 2) {
sbi->s_log_groups_per_flex = 0;
return 1;
}
but resize is unconditionally doing this in ext4_group_add as long as the
FLEX_BG feature is set:
atomic_add(input->free_blocks_count,
&sbi->s_flex_groups[flex_group].free_blocks);
so for a NULL s_flex groups it went boom.
Every other access to ->s_flex_groups checks s_log_groups_per_flex first, so
this should be the proper fix:
Index: linux-2.6/fs/ext4/resize.c
===================================================================
--- linux-2.6.orig/fs/ext4/resize.c
+++ linux-2.6/fs/ext4/resize.c
@@ -930,7 +930,8 @@ int ext4_group_add(struct super_block *s
percpu_counter_add(&sbi->s_freeinodes_counter,
EXT4_INODES_PER_GROUP(sb));
- if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
+ sbi->s_log_groups_per_flex) {
ext4_group_t flex_group;
flex_group = ext4_flex_group(sbi, input->group);
atomic_add(input->free_blocks_count,
This fixes the reproducer, need to double check it on Alessandro's image.
-Eric
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