Re: [PATCH] resize: check s_log_groups_per_flex before accessing flex groups

[tytso@mit.edu]

On Sun, Mar 28, 2010 at 09:14:07AM -0600, Andreas Dilger wrote:
> On 2010-03-27, at 13:32, Eric Sandeen wrote:
> >#13549, Kernel oops while online resizing of an ext4 filesystem
> >
> >if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
> >and every other access to this first tests s_log_groups_per_flex;
> >same thing needs to happen in resize or we'll wander off into
> >a null pointer.
> 
> Does it even make sense to set INCOMPAT_FLEX_BG if we only have a
> single group per flexbg?  That is just a normal filesystem then.
> That would be a separate bug in mke2fs.

Yes, it does make sense to set flex_bg in this case; it allows the
group metadata to be stored outside of a blockgroup, which is helpful
to e2fsck in some cases when it needs to relocate an inode table and
there's no contiguous free space available in the block group.

	   	      	   	 	   - Ted