Date: Fri, 24 Jun 2011 14:06:27 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Peter Holm <peter@holm.cc> Cc: freebsd-current@freebsd.org Subject: Re: Thoughts on TMPFS no longer being considered "highly experimental" Message-ID: <20110624110627.GW48734@deviant.kiev.zoral.com.ua> In-Reply-To: <20110624103016.GA71991@x2.osted.lan> References: <20110623163109.GA508@dragon.NUXI.org> <20110623202153.GS48734@deviant.kiev.zoral.com.ua> <20110624103016.GA71991@x2.osted.lan>
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On Fri, Jun 24, 2011 at 12:30:16PM +0200, Peter Holm wrote:
> On Thu, Jun 23, 2011 at 11:21:53PM +0300, Kostik Belousov wrote:
> > On Thu, Jun 23, 2011 at 09:31:09AM -0700, David O'Brien wrote:
> > > Does anyone object to this patch?
> > >=20
> > > David Wolfskill and I have run TMPFS on a number of machines for two
> > > years with no problems.
> > >=20
> > > I may have missed something, but I'm not aware of any serious PRs on
> > > TMPFS either.
> > >=20
> > >=20
> > > Index: tmpfs_vfsops.c
> > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > > --- tmpfs_vfsops.c (revision 221113)
> > > +++ tmpfs_vfsops.c (working copy)
> > > @@ -155,9 +155,6 @@ tmpfs_mount(struct mount *mp)
> > > return EOPNOTSUPP;
> > > }
> > > =20
> > > - printf("WARNING: TMPFS is considered to be a highly experimental "
> > > - "feature in FreeBSD.\n");
> > > -
> > > vn_lock(mp->mnt_vnodecovered, LK_SHARED | LK_RETRY);
> > > error =3D VOP_GETATTR(mp->mnt_vnodecovered, &va, mp->mnt_cred);
> > > VOP_UNLOCK(mp->mnt_vnodecovered, 0);
> >=20
> > The things I am aware of:
> > - there is a races on the lookup. They were papered over in r212305,
> > but the bug was not really fixed, AFAIR.
> >=20
> > - the tmpfs does double-buffering for the mapped vnodes. This is quite
> > insulting for the memory-backed fs, isn't it ? I have a patch, but it is
> > still under review.
> >=20
> > - I believe Peter Holm has more test cases that fails with tmpfs. He
> > would have more details. I somewhat remember some panic on execve(2) the
> > binary located on tmpfs.
> >=20
>=20
> I ran the TMPFS tests I have and so far I only spotted the mmap(2)
> problem:
>=20
> http://people.freebsd.org/~pho/stress/log/tmpfs/
It would be indeed good if the issue was the only remaining problem.
The deadlock in tmpfs6.txt is caused by doing copyin() while having
a page busied. This should be fixed indirectly by the patch to
avoid double-buffering, I uploaded the latest version at
http://people.freebsd.org/~kib/misc/tmpfs.5.patch
>=20
> > Removing the warning will not make the issues coming away.
>=20
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