Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-qa0-f52.google.com ([209.85.216.52]:56989 "EHLO mail-qa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754847AbaGNNAb (ORCPT ); Mon, 14 Jul 2014 09:00:31 -0400 Received: by mail-qa0-f52.google.com with SMTP id j15so3124298qaq.25 for ; Mon, 14 Jul 2014 06:00:31 -0700 (PDT) From: Jeff Layton Date: Mon, 14 Jul 2014 09:00:28 -0400 To: NeilBrown Cc: Jeff Layton , Trond Myklebust , Alexander Viro , NFS Subject: Re: [PATCH] NFS: nfs4_lookup_revalidate need to report STALE inodes. Message-ID: <20140714090028.6f04fd2c@tlielax.poochiereds.net> In-Reply-To: <20140714223513.47807c98@notabene.brown> References: <20140714151405.2fa06dd7@notabene.brown> <20140714081455.69f55224@tlielax.poochiereds.net> <20140714223513.47807c98@notabene.brown> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/7oYy9cPls=.whDZ5dBL2yPt"; protocol="application/pgp-signature" Sender: linux-nfs-owner@vger.kernel.org List-ID: --Sig_/7oYy9cPls=.whDZ5dBL2yPt Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Mon, 14 Jul 2014 22:35:13 +1000 NeilBrown wrote: > On Mon, 14 Jul 2014 08:14:55 -0400 Jeff Layton > wrote: >=20 > > On Mon, 14 Jul 2014 15:14:05 +1000 > > NeilBrown wrote: > >=20 > > >=20 > > > If an 'open' of a file in an NFSv4 filesystem finds that the dentry is > > > in cache, but the inode is stale (on the server), the dentry will not > > > be re-validated immediately and may cause ESTALE to be returned to > > > user-space. > > >=20 > > > For a non-create 'open', do_last() calls lookup_fast() and on success > > > will eventually call may_open() which calls into nfs_permission(). > > > If nfs_permission() makes the ACCESS call to the server it will get > > > NFS4ERR_STALE, resulting in ESTALE from may_open() and thence from > > > do_last(). > > > The retry-on-ESTALE in filename_lookup() will repeat exactly the same > > > process because nothing in this path will invalidate the dentry due to > > > the inode being stale, so the ESTALE will be returned. > > >=20 > > > lookup_fast() calls ->d_revalidate(), but for an OPEN on an NFSv4 > > > filesystem, that will succeed for regular files: > > > /* Let f_op->open() actually open (and revalidate) the file */ > > >=20 > > > Unfortunately in the case of a STALE inode, f_op->open() never gets > > > called. If we teach nfs4_lookup_revalidate() to report a failure on > > > NFS_STALE() inodes, then the dentry will be invalidated and a full > > > lookup will be attempted. The ESTALE errors go away. > > >=20 > > >=20 > > > While I think this fix is correct, I'm not convinced that it is > > > sufficient, particularly if lookupcache=3Dnone. > > > The current code will fail an "open" is nfs_permission() fails, > > > without having performed a LOOKUP. i.e. it will use the cache. > > > nfs_lookup_revalidate will force a lookup before the permission check > > > if NFS_MOUNT_LOOKUP_CACHE_NONE, but nfs4_lookup_revalidate will not. > > >=20 > >=20 > > This patch should make the code fall through to nfs_lookup_revalidate, > > which would then force the lookup, right? >=20 > Yes ... though maybe that's not what I really want to do. I really wante= d to > just return '0', though I would need to check that is right in all cases. >=20 > >=20 > > Also, I'm a little unclear... > >=20 > > Why would may_open fail with ESTALE after the v4 OPEN succeeds? The > > OPEN should be returning a filehandle and attributes for the inode > > actually opened. It seems like we ought to be doing any permission > > checks vs. that inode, not anything we had in cache. Presumably the > > server is then holding it open so it shouldn't be stale. >=20 > may_open is called *before* and v4 OPEN. >=20 > In do_last, if the inode is already in cache, then > lookup_fast is called, which calls d_revalidate > then may_open (calls ->permission) > then finish_open which calls f_op->open >=20 > Yes, we should be doing permission checking against whatever 'open' finds. > But the VFS is structured to the the permission check after d_revalidate = and > before ->open. So maybe d_revalidate needs to do the NFS open?? >=20 Ok, I see. Ugh, having the revalidate do the open sounds...messy. A simpler fix might be to fix it so that an -ESTALE return from may_open triggers a retry. Something like this maybe (probably whitespace damaged, so just for discussion purposes): diff --git a/fs/namei.c b/fs/namei.c index 985c6f368485..c1657deea52c 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3045,8 +3045,13 @@ finish_open: } finish_open_created: error =3D may_open(&nd->path, acc_mode, open_flag); - if (error) + if (error) { + if (error =3D=3D -ESTALE) + goto stale_open; goto out; + } file->f_path.mnt =3D nd->path.mnt; error =3D finish_open(file, nd->path.dentry, NULL, opened); if (error) { ...though might need to convert the ESTALE to EOPENSTALE there too, not sure... >=20 > >=20 > > Are we not properly updating the dcache (and attrcache) after the > > OPEN reply? >=20 > I think so, yes. But in the problem case, we don't even send an OPEN > request. >=20 >=20 > >=20 > > >=20 > > > Signed-off-by: NeilBrown > > >=20 > > > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > > > index 4a3d4ef76127..4f7414afca27 100644 > > > --- a/fs/nfs/dir.c > > > +++ b/fs/nfs/dir.c > > > @@ -1563,6 +1563,8 @@ static int nfs4_lookup_revalidate(struct > > > dentry *dentry, unsigned int flags) /* We cannot do exclusive > > > creation on a positive dentry */ if (flags & LOOKUP_EXCL) > > > goto no_open_dput; > > > + if (NFS_STALE(inode)) > > > + goto no_open_dput; > > > =20 > > > /* Let f_op->open() actually open (and revalidate) the > > > file */ ret =3D 1; > >=20 > > Looks legit to me too, but it seems like the inode could go stale > > w/o us knowing after this point. > >=20 > > Acked-by: Jeff Layton >=20 > Thanks, > NeilBrown --=20 Jeff Layton --Sig_/7oYy9cPls=.whDZ5dBL2yPt Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBAgAGBQJTw9RsAAoJEAAOaEEZVoIVy1IQANCseB2MkPJepgXQeZM0wbVV c0+NosubW3qULc5hDgjWmoTBZMhtgGiwXn6k5hRRTf47g4DOqoJzIgXFxBHL+zlY BTJWLm2E2IZmYHLhDd5+BdkgnJrYXDD06u/QMXzOACQDRevdKryRiXwuzC/ziOnE gIxsjAQjIRo6c1MUHe3RAvYn7vnvJiGJTQo2fjIkcAmiqlfW9kjdr5qexf30lWoE 2rPqjNB4ar6nUHk9fQwIGWo1WNrXkNvuSkb/mfmEVmCPyRTKaD1SELobH4jmVaNF hVw7o5e4mVWl2aMHsOlQJ/bUjfgFotzxfoPG389WR2qSWfRWE5OZUFSXNf0x7nkh y0MegqlF3Dj9YEMyLtciiCoB3qbGC8Kp6qCfJ7THkApBSY2V+InGN8nKvWtWebQB ocpb9Bku5GHA9IUWpKyvNddwnnuoX5wrjcZjgPz8aBKCsUNxnGdR+flJz7+xLDqC KrM/u4qD4lt4g1M0WKtBRpZht6mIwTCfg8/fnqC9SEWXQf0ywOkgf2ocCWSLqgsc fwstywZTV73+zYsXdJmNo4Esbo0oYpaDYb9miZb06t8qfNU/ma5usgarDFfC7FDv E3mAXMao6vpvH5d0eH+PsNnrF+Ubt9G/M2pj5hdS+CLrRNXdY8AVRAs/f4YjHbaS y0eztc6e8XZa3/QJECuS =RkPl -----END PGP SIGNATURE----- --Sig_/7oYy9cPls=.whDZ5dBL2yPt--