Re: [PATCH] ext4: Use superblock s_raid_stripe_width as stripe size during block allocation.

[Andreas Dilger <adilger@sun.com>]

On Jan 10, 2008  09:58 +0530, Aneesh Kumar K.V wrote:
> > d) if s_stripe is still > s_blocks_per_group try s_raid_stride
> > e) if s_stripe is still > s_blocks_per_group use 0
> 
> But i guess mke2fs and tune2fs should validate the value of
> s_raid_stripe_width and s_raid_stride. Both of them should be less that
> blocks per group. Should I add extra check in the kernel for them ?

It's true that mke2fs and tune2fs should validate this, but it is also
possible to become corrupted, and e2fsck doesn't fix it yet nor can it
make a good estimate of the right value.

> > > +	if (!sbi->s_stripe ||
> > > +			sbi->s_stripe >= sbi->s_blocks_per_group) {
> > 
> 
> So what do you think should it be > or >=. Looking at the mballoc I
> guess it should work with stripe size equal to blocks per group. I am
> not sure how efficient the allocation would be though.

I think if s_stripe == s_blocks_per_group that is fine...  For 1kB block
filesystem that is only 8MB in size.

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