Re: [PATCH 0/20] return f_fsid for statfs(2)

From: Dave Kleikamp
Date: Mon Jan 19 2009 - 14:29:23 EST

These patches probably belong in linux-fsdevel, but I hesitate to ask
you to repost all twenty.

On Tue, 2009-01-20 at 01:30 +0800, Coly Li wrote:
> Currently many file systems in Linux kernel do not return f_fsid in statfs info, the value is set as
> 0 in vfs layer. Anyway, in some conditions, f_fsid from statfs(2) is useful, especially being used
> as (f_fsid, ino) pair to uniquely identify a file.
> Basic idea of the patches is generating a unique fs ID by huge_encode_dev(sb->s_bdev->bd_dev) during
> file system mounting life time (no endian consistent issue). sb is a point of struct super_block of
> current mounted file system being accessed by statfs(2).

ext[234] return a portion of the uuid in f_fsid. There is a theoretical
chance of those values being non-unique. Since there doesn't appear to
be any case for the fsid to be persistent between boots, I guess
huge_encode_dev() is probably a better choice. In practice it probably
makes no difference.

> The patches are quite simple, any feedback or patch review is welcome.

They look reasonable to me.

David Kleikamp
IBM Linux Technology Center

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