Re: [PATCH] Btrfs: do not loop through raid types when looking for free extent

[Chris Mason <chris.mason@oracle.com>]

Excerpts from Yan, Zheng's message of 2010-11-16 20:38:23 -0500:
> On Wed, Nov 17, 2010 at 5:22 AM, Josef Bacik <josef@redhat.com> wrote=
:
> > There is a bug in find_free_extent where if we don't find a free ex=
tent in the
> > raid type we are looking for, we loop through to the next raid type=
=2E =C2=A0This is
> > not ok since we need to make sure we honor the raid types we are gi=
ven. =C2=A0So
> > instead kill this check and get the proper index for the raid type =
we want from
> > the allocator. =C2=A0Thanks,
> >
>=20
> Loop through raid types is for handling failure in the middle of raid=
 type
> conversion.

The problem is that nothing prevents it from looping back to a raid0
chunk when we really want raid1 or raid10.  And mkfs leaves behind a
small raid0 chunk (4MB) that is uses as it assembles all the devices.

I confirmed that we often use the small raid0 chunk even in raid1 or
raid10.

Please take a look at this commit:

http://git.kernel.org/?p=3Dlinux/kernel/git/mason/btrfs-unstable.git;a=3D=
commit;h=3D83a50de97fe96aca82389e061862ed760ece2283

-chris
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