From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBEFD24BD0B for ; Mon, 10 Feb 2025 17:20:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739208054; cv=none; b=UCzQeLRQW7h2dr7K/oATpPn6++tMtw8VGihOSf1uVTNFRoeiZLjpMgPhNGzw+VVesv3HFvfS3YryhRLCzNBmeSe/YNT2iQqFLv2H21Ae4msCLnIKwc3CxZuLfLswWp7ZS/0pqaDZ/4p/uoHd3y4rfJXrN2R97pSnyF3Brg1/nXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739208054; c=relaxed/simple; bh=nu2CNJMBDsCc5bi3XQry8yMmOGDpbWrDSQfdCEvXzq0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=rNdAQFiBSUKDfZXcL1BJ5Qu3OO7vWVo38PgO5i5aDmo3SW64U/FpRiJZURP44HR5JgYylxtWOGgqGlL+ipS640TqqsojOoEzyvOctZgDAWqN8T/pW7hPPnquRplB0QhnG04PixKHuJG/lYBYMvdG7xGqUxDliKjk8vHdEGdbyJc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dY2HXXZ5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dY2HXXZ5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9EC6C4CEE6; Mon, 10 Feb 2025 17:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739208054; bh=nu2CNJMBDsCc5bi3XQry8yMmOGDpbWrDSQfdCEvXzq0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=dY2HXXZ5pqTnPwTfPyqYF/zoWsNLYqCUl6ITIkYh8zE72whEyZvay+TuelIcbWdOR lTpeQybu6D9qDnjpzyAqu4LiZVUkH28OTk5QLl9CFOb6wikO1b3oxPy18dfhHuMKVu r9sAmVXFK9HNR1L+Gtr1w6wMovvIlG3lH0AhAneUnQpiqDJ+7wGy7HOhAVUwLeskn3 7AbkfwnxSO4ypM5yqhEklPb7PVZB88MGCAhkjoke9JQ8t7U5ZqIelBvs6HC2tmvyFG Wr4j7T8qyj9UQDZiJ7fCiTHz63NDcPMfNNe7unX6ylWtNGioQjog9riInxnYrEsioQ NtzMDgiS3o2BQ== Message-ID: <10f2778fe0efd8f081a19d5a3200eb1d49147a06.camel@kernel.org> Subject: Re: [PATCH v4] nfsd: disallow file locking and delegations for NFSv4 reexport From: Jeff Layton To: cel@kernel.org, Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Mike Snitzer Date: Mon, 10 Feb 2025 12:20:52 -0500 In-Reply-To: <20250210162553.112705-1-cel@kernel.org> References: <20250210162553.112705-1-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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We do not and cannot support file locking with NFS reexport over > NFSv4.x for the same reason we don't do it for NFSv3: NFS reexport > server reboot cannot allow clients to recover locks because the source > NFS server has not rebooted, and so it is not in grace.=C2=A0 >=20 Refresh my memory: how do we prevent this in v3? It seems like NLM should use the same mechanism. > Since the > source NFS server is not in grace, it cannot offer any guarantees that > the file won't have been changed between the locks getting lost and > any attempt to recover/reclaim them. The same applies to delegations > and any associated locks, so disallow them too. >=20 > Clients are no longer allowed to get file locks or delegations from a > reexport server, any attempts will fail with operation not supported. >=20 > Update the "Reboot recovery" section accordingly in > Documentation/filesystems/nfs/reexport.rst >=20 > Signed-off-by: Mike Snitzer > Signed-off-by: Chuck Lever > --- > Documentation/filesystems/nfs/reexport.rst | 10 +++++++--- > fs/nfs/export.c | 3 ++- > fs/nfsd/nfs4state.c | 18 ++++++++++++++++++ > include/linux/exportfs.h | 14 +++++++++++++- > 4 files changed, 40 insertions(+), 5 deletions(-) >=20 >=20 > Jeff and I believe that it is better to prevent data corruption for > now than to continue to enable risky use cases. Thus I've forward- > ported this patch to v6.14-rc2 and intend to include it in the > nfsd-6.15 pull request. >=20 > We remain open to considering solutions that enable locking through > to the back-end NFS server with appropriate lock recovery. >=20 >=20 > diff --git a/Documentation/filesystems/nfs/reexport.rst b/Documentation/f= ilesystems/nfs/reexport.rst > index ff9ae4a46530..044be965d75e 100644 > --- a/Documentation/filesystems/nfs/reexport.rst > +++ b/Documentation/filesystems/nfs/reexport.rst > @@ -26,9 +26,13 @@ Reboot recovery > --------------- > =20 > The NFS protocol's normal reboot recovery mechanisms don't work for the > -case when the reexport server reboots. Clients will lose any locks > -they held before the reboot, and further IO will result in errors. > -Closing and reopening files should clear the errors. > +case when the reexport server reboots because the source server has not > +rebooted, and so it is not in grace. Since the source server is not in > +grace, it cannot offer any guarantees that the file won't have been > +changed between the locks getting lost and any attempt to recover them. > +The same applies to delegations and any associated locks. Clients are > +not allowed to get file locks or delegations from a reexport server, any > +attempts will fail with operation not supported. > =20 > Filehandle limits > ----------------- > diff --git a/fs/nfs/export.c b/fs/nfs/export.c > index be686b8e0c54..e9c233b6fd20 100644 > --- a/fs/nfs/export.c > +++ b/fs/nfs/export.c > @@ -154,5 +154,6 @@ const struct export_operations nfs_export_ops =3D { > EXPORT_OP_CLOSE_BEFORE_UNLINK | > EXPORT_OP_REMOTE_FS | > EXPORT_OP_NOATOMIC_ATTR | > - EXPORT_OP_FLUSH_ON_CLOSE, > + EXPORT_OP_FLUSH_ON_CLOSE | > + EXPORT_OP_NOLOCKS, > }; > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index b42e2ab7a042..f0fb6ca4b70c 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -6000,6 +6000,15 @@ nfs4_set_delegation(struct nfsd4_open *open, struc= t nfs4_ol_stateid *stp, > if (!nf) > return ERR_PTR(-EAGAIN); > =20 > + /* > + * File delegations and associated locks cannot be recovered if the > + * export is from an NFS proxy server. > + */ > + if (exportfs_cannot_lock(nf->nf_file->f_path.mnt->mnt_sb->s_export_op))= { > + nfsd_file_put(nf); > + return ERR_PTR(-EOPNOTSUPP); > + } > + > spin_lock(&state_lock); > spin_lock(&fp->fi_lock); > if (nfs4_delegation_exists(clp, fp)) > @@ -8140,6 +8149,10 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_co= mpound_state *cstate, > status =3D fh_verify(rqstp, &cstate->current_fh, S_IFREG, 0); > if (status !=3D nfs_ok) > return status; > + if (exportfs_cannot_lock(cstate->current_fh.fh_dentry->d_sb->s_export_o= p)) { > + status =3D nfserr_notsupp; > + goto out; > + } > =20 > if (lock->lk_is_new) { > if (nfsd4_has_session(cstate)) > @@ -8479,6 +8492,11 @@ nfsd4_locku(struct svc_rqst *rqstp, struct nfsd4_c= ompound_state *cstate, > status =3D nfserr_lock_range; > goto put_stateid; > } > + if (exportfs_cannot_lock(nf->nf_file->f_path.mnt->mnt_sb->s_export_op))= { > + status =3D nfserr_notsupp; > + goto put_file; > + } > + > file_lock =3D locks_alloc_lock(); > if (!file_lock) { > dprintk("NFSD: %s: unable to allocate lock!\n", __func__); > diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h > index 4cc8801e50e3..ca6c605072c7 100644 > --- a/include/linux/exportfs.h > +++ b/include/linux/exportfs.h > @@ -259,10 +259,22 @@ struct export_operations { > atomic attribute updates > */ > #define EXPORT_OP_FLUSH_ON_CLOSE (0x20) /* fs flushes file data on close= */ > -#define EXPORT_OP_ASYNC_LOCK (0x40) /* fs can do async lock request */ > +#define EXPORT_OP_NOLOCKS (0x40) /* no file locking support */ > unsigned long flags; > }; > =20 > +/** > + * exportfs_cannot_lock() - check if export implements file locking > + * @export_ops: the nfs export operations to check > + * > + * Returns true if the export does not support file locking. > + */ > +static inline bool > +exportfs_cannot_lock(const struct export_operations *export_ops) > +{ > + return export_ops->flags & EXPORT_OP_NOLOCKS; > +} > + > extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid= , > int *max_len, struct inode *parent, > int flags); Aside from the question about NLM, this looks good: Reviewed-by: Jeff Layton