Re: [PATCH] Btrfs: add a disk info ioctl to get the disks attached to a filesystem

[Lennart Poettering <lennart@poettering.net>]

On Thu, 30.09.10 21:59, Kay Sievers (kay.sievers@vrfy.org) wrote:

> > So my question is, is this what we want? =A0Do I just need to quit =
bitching and
> > make it work? =A0Or am I doing something wrong? =A0This is a comple=
tely new area for
> > me so I'm just looking around at what md/dm does and trying to mirr=
or it for my
> > own uses, if thats not what I should be doing please tell me, other=
wise this
> > seems like alot of work for a very shitty solution to our problem. =
=A0Thanks,
>=20
> Yeah, that matches what I was experiencing when thinking about the
> options. Making a btrfs mount a fake blockdev of zero size seems like
> a pretty weird hack, just get some 'dead' directories in sysfs. A
> btrfs mount is just not a raw blockdev, and should probably not
> pretend to be one.
>=20
> I guess a statfs()-like call from the filesystem side and not the
> block side, which can put out such information in some generic way,
> would better fit here.

Note that for my particular usecase it would even suffice to have two
flags in struct statfs or struct statvfs that encode whether there's a =
at
least one SSD in the fs, resp. at least one rotating disk in the fs.

if (statvfs.f_flag & ST_SSD)=20
        printf("FS contains at least one SSD disk");
if (statvfs.f_flag & ST_ROTATING)=20
        printf("FS contains at least one rotating disk");

Lennart

--=20
Lennart Poettering - Red Hat, Inc.
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