[Gluster-devel] Lazy umount emulation

Krishnan Parthasarathi kparthas at redhat.com
Tue Sep 9 06:03:28 UTC 2014


IIRC, lazy umount is being used in glusterd to avoid leaving
behind an entry in /etc/mtab, for every internal mount that
failed to unmount for some reason. replace-brick command doesn't
have a requirement that the umount must happen in a lazy manner.


----- Original Message -----
> Hi
> Lazy umount is a Linux-only feature that let userland tell the kernel to
> umount a filesystem as soon as it drops the last reference to it. It is
> used at a few places by GlusterFS and is a portability problem.
> brick-replace will not currently work without it, which is a critical
> problem.
> I wrote a basic lazy umount emulation: it spawn a thread that will try
> periodically try to umount. Could someone review?
> http://review.gluster.com/8649
> For now the prototype is
> int gf_umount_lazy (char *xlname, char *path);
> The thing could be factorized further: if this is considered useful, I
> can do a umount wrapper with a flag argument which value could be
> GF_MNT_LAZY, GF_MNT_FORCE. I can also add a timeout to the periodical
> lazy umount attemps. Please comment.
> --
> Emmanuel Dreyfus
> http://hcpnet.free.fr/pubz
> manu at netbsd.org
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