Date: Sat, 12 Jun 2010 17:15:49 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Mikolaj Golub <to.my.trociny@gmail.com> Cc: Leon Me??ner <l.messner@physik.tu-berlin.de>, freebsd-stable@freebsd.org Subject: Re: freeBSD nullfs together with nfs and "silly rename" Message-ID: <20100612141549.GM13238@deviant.kiev.zoral.com.ua> In-Reply-To: <8639wsk4t1.fsf@kopusha.home.net> References: <20100606144443.GA50876@emmi.physik-pool.tu-berlin.de> <8639wsk4t1.fsf@kopusha.home.net>
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--Cqq5NadOW2RfLMJ/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jun 12, 2010 at 11:56:10AM +0300, Mikolaj Golub wrote: >=20 > On Sun, 6 Jun 2010 16:44:43 +0200 Leon Me??ner wrote: >=20 > LM> Hi, > LM> I hope this is not the wrong list to ask. Didn't get any answers on > LM> -questions. >=20 > LM> When you try to do the following inside a nullfs mounted directory, > LM> where the nullfs origin is itself mounted via nfs you get an error: >=20 > LM> # foo=20 > LM> # tail -f foo&=20 > LM> # rm -f foo=20 > LM> tail: foo: Stale NFS file handle > LM> # fg >=20 > LM> This is really a problem when running services inside jails and using > LM> NFS as storage. As of [2] it looks like this problem is known for a > LM> while. On a normal NFS mount this does not happen as "silly renaming" > LM> [1] works there (producing nasty little .nfsXXXX files). >=20 > nfs_sillyrename() is called when vnode's usecount is more then 1. It is > expected that unlink() syscall increases vnode's usecount in namei() and = if > the file has been already opened usecount will be more then 1. >=20 > But with nullfs layer present the reference counts are held by the upper = node, > not the lower (nfs) one, so when unlink() is called it increases usecount= of > the upper vnode, not nfs vnode and nfs_sillyrename() is never called. >=20 > The strightforward solution looks like to implement null_remove() that wi= ll > increase lower vnode's refcount before calling null_bypass() and then > decrement it after the call. See the attached patch (it works for me on b= oth > 8-STABLE and CURRENT). The upper vnode holds a reference to the lower vnode, as you noted. Now, with your patch, I believe that _all_ calls to the nfs_remove() are happen with refcount > 1. --Cqq5NadOW2RfLMJ/ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkwTlpUACgkQC3+MBN1Mb4gkRwCg4QvbVcDxkzdEgeMmtKUpgDP4 F2AAnj+DyLLiPVvIe+7/bjdyKb87oy1f =Jmsd -----END PGP SIGNATURE----- --Cqq5NadOW2RfLMJ/--
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