On Wed, Dec 01, 2010 at 03:09:52PM -0500, Josef Bacik wrote:
> On Wed, Dec 01, 2010 at 03:00:08PM -0500, J. Bruce Fields wrote:
> > On Wed, Dec 01, 2010 at 02:54:33PM -0500, Josef Bacik wrote:
> > > Oh well crud, I was hoping that I could leave the inode numbers as 256 for
> > > everything, but I forgot about readdir. So the inode item in the parent
> > > would
> > > have to have a unique inode number that would get spit out in readdir,
> > > but then
> > > if we stat'ed the directory we'd get 256 for the inode number. Oh well,
> > > incompat flag it is then.
> >
> > I think you're already fine:
> >
> > # mkdir TMP
> > # dd if=/dev/zero of=TMP-image bs=1M count=512
> > # mkfs.btrfs TMP-image
> > # mount -oloop TMP-image TMP/
> > # btrfs subvolume create sub-a
> > # btrfs subvolume create sub-b
> > ../readdir-inos .
> > . 256 256
> > .. 256 4130609
> > sub-a 256 256
> > sub-b 257 256
> >
> > Where readdir-inos is my silly test program below, and the first number is
> > from
> > readdir, the second from stat.
> >
>
> Heh as soon as I typed my email I went and actually looked at the code, looks
> like for readdir we fill in the root id, which will be unique, so hotdamn we
> are
> good and I don't have to use a stupid incompat flag. Thanks for checking that
> :),
My only complaint was just about how you said this:
"When you create a subvolume, the directory inode that is
created in the parent subvolume has the inode number of 256"
If you revise that you might want to clarify. (Maybe "Every subvolume
has a root directory inode with inode number 256"?)
The way you've stated it sounds like you're talking about the
readdir-returned number, which would normally come from the inode that
has been covered up by the mount, and which really is an inode in the
parent filesystem....
--b.
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