Re: [PATCH, RFC V3] ext4: limit block allocations for indirect-block files to < 2^32

[Andreas Dilger <adilger@sun.com>]

On Sep 10, 2009  16:16 -0500, Eric Sandeen wrote:
> Any suggestions on the naming issues?  (what's the official name for a
> "not-extent-based-file?")

I've always used "block mapped" (i.e. mapped block-by-block) vs.
"extent mapped".

> However, Ric just ran a massive fs_mark test on a 60T filesystem that he
> created with "mke2fs" (no extents and no journal - accidentally) and we
> got no corruption even without this patch.
> 
> I need to see if a filesystem w/o the extents feature (at all, vs. some
> old-format files on an extents fs) never even tries to allocate past
> 2^32; I didn't think so, but now not so sure.

Well, it may depend a lot on which inodes are in use.  That will set the
goal block, and may prevent any above-16TB allocations.  Either you could
fill the bitmaps with 0xff (and zero the free blocks counters, to avoid
problems with mballoc), or actually fill the first 16TB of the filesystem.

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