Re: [PATCH] ext4: add checksum calculation when clearing UNINIT flag

[Andreas Dilger <adilger@sun.com>]

On Nov 07, 2008  09:38 -0500, Theodore Ts'o wrote:
> On Fri, Nov 07, 2008 at 07:57:18PM +0530, Aneesh Kumar K.V wrote:
> > Because when we clear the uninitt_bg flag the kernel expect the block 
> > bitmap to be correctly indicate blocks containing block
> > bitmap and inode bitmap as used. If mke2fs didn't do that we would
> > need to do the same when we remove the uninit_bg flag.
> 
> We have separate flags inidicating whether the block allocation bitmap
> and inode allocation bitmaps are initialized or not,
> EXT4_BG_BLOCK_UNINIT, and EXT4_BG_INODE_UNINIT, respectively.  So what
> I am proposing is to not initialize the block bitmap in
> ext4_new_inode(), and not to clear the EXT4_BG_BLOCK_UNINIT flag, either.

That would be dangerous, because the block group _would_ be in use due
to the fact that one of the inode table blocks is in use.  That isn't
to say we couldn't adopt sematics as you suggest (e.g. that INODE_UNINIT
not being set implies that the inode table blocks are in use regardless
of whether or not BLOCK_UNINIT is set, but it needs careful consideration.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.