[OLPC-devel] Booting from uncleanly dismounted flash key.

[David Woodhouse]

On Sat, 2006-08-26 at 05:41 -0500, Richard Smith wrote:
> > >
> > > Is there some way to fix this?  This feels very fragile to me.
> >
> > Just to be clear: this is _expected_ behaviour. Ext3 is
> > backward-compatible with ext2 _if_ it's mounted uncleanly and the
> > journal is clear. If there are writes outstanding in the journal then it
> > is not compatible with ext2. Thus the refusal to mount, with an error
> > message about incompatible features.
> 
> That may be the error I've seen.  Not sure why a reset would fix it though.
> 
> How much of as space hit are we going to take if we use ext3 rather
> than ext2 in the boot kernel?

Quite a lot -- 88390 bytes or so with a normal build with GCC 4.1.1:

   text    data     bss     dec     hex filename
  42582    1028       8   43618    aa62 fs/ext2/ext2.o
  93173    1252       8   94433   170e1 fs/ext3/ext3.o
  37547       8      20   37575    92c7 fs/jbd/jbd.o

(Or 86617 bytes if you're building it all with --combine:
   text    data     bss     dec     hex filename
  41636    1028       8   42672    a6b0 fs/ext2/ext2.o
  91944    1252       8   93204   16c14 fs/ext3/ext3.o
  36057       8      20   36085    8cf5 fs/jbd/jbd.o )

We might do better with a simple "journal replay" hack -- we could lift
the code out of fsck.ext3.

-- 
dwmw2