On Tue, Mar 30, 2010 at 08:36:17PM +0800, jing zhang wrote: > --- linux-2.6.32/fs/ext4/mballoc.c 2009-12-03 11:51:22.000000000 +0800 > +++ ext4_mm_leak/mballoc-13.c 2010-03-30 20:28:08.000000000 +0800 > @@ -4183,12 +4183,20 @@ static int ext4_mb_discard_preallocation > ext4_group_t i, ngroups = ext4_get_groups_count(sb); > int ret; > int freed = 0; > + static ext4_group_t grp_cache = 0; This is a problem right there. Remember that there could be multiple file systems mounted so a static variable is fundamentally flawed. In fact, we could have a one filesystem which has more than 3 times the number of groups as another file system. I'll leave it as an exercise to a reader why your patch would be fundamentally flawed in that case. The other thing to note is that this case only gets hit if the file system is so full that we need to empty preallocations. So this means hitting this case is rare, which raises two questions: (1) is it worth it to optimize this case in the first place (is it really that expensive to iterate over all the groups to discard the preallocations); (2) can we test this case well? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
