On 2011-02-14, at 0:52, "Amir G." [off-list ref] wrote:

quoted

@@ -1160,7 +1160,15 @@ ext4_mb_load_buddy(struct super_block *sb,

+       /*
+        * We only need to take the read lock if other groups share the buddy
+        * page with this group or if blocks may be added to this (last) group
+        * by ext4_group_extend().
+        */
+       if (blocks_per_page > 2 || group == sbi->s_groups_count - 1)
+               e4b->alloc_semp = &grp->alloc_sem;

No comment on whether this change is safe or not, but shouldn't this check be:

        if (blocks_per_page > 1 ||

Cheers, Andreas