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 CA9E924168A for ; Tue, 29 Apr 2025 16:54:30 +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=1745945670; cv=none; b=ewOggKr3Wlkpu8dZpKP3PwsGlHbG4mxvyFUiwBl6sES/FsMx1Uz7F9zRXxYGM/N1y3KxvlCDybbcmdtOoJSqkKFCM18pBzYQRyLGDSqTd508ZosS4C9k3V/u9rQnXcngGbN/nUqN0wUlE6NvyETAvHDMJpmsxjaHLcNYhrrLRh8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745945670; c=relaxed/simple; bh=PHIHdUE9RS7Ttq0eJdrJI94inAlrNPeY+I7Z3pivoS4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Ufti/2Di4X8bJYxgXvszComv8ZFQzo55L7MGiY1nqBtFx7kgaFmCGGC4moN0REBsXMrcX0vfcvmjf0+erECV0G95aSZBYpmZJe4nrDtzXpeqiM4R/X6zyZNqdx4uXRgMvKsqEUrtTp3+IVRY09uFiRZKrXIAOxB5v5EbvKkoiUY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LWOy6KMw; 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="LWOy6KMw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84D8FC4CEE3; Tue, 29 Apr 2025 16:54:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745945670; bh=PHIHdUE9RS7Ttq0eJdrJI94inAlrNPeY+I7Z3pivoS4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=LWOy6KMwTvwQFNGEhVjUT+Ssya5hSAG8C6GBaCxvea/dxtBnK9YAHS0EI+MQWhrK9 ya/ra5tHxgsK5q5Fw9U7pkedk31LK8D8j2yygxQetiHzWE2tE9q9JPvSWIirs87xEL RxjEvbEkkgLMRmgEBpGzRWmEKwbyRbZa6vnoBAK0UY7Aj7hyLkFcQK4D4zSPGi7Oa5 2HLDVIDYamPXphExequAcx6fSu7V7hrBKMVhXoV5O8xIKMRo132vp08FM3d9PFymN9 EMsUf5jv/Qy2rfS4gxspUOQLEP0VA6JdCBqENBGklG9YOi53/lKWc4fL0gDT6GuLVZ x0e6gbUCHA7QA== Message-ID: <9a09c8681702df0d8a1e3cefb8fb75113e1677b9.camel@kernel.org> Subject: Re: [PATCH] NFS: Avoid flushing data while holding directory locks in nfs_rename() From: Jeff Layton To: Chuck Lever , trondmy@kernel.org, Anna Schumaker Cc: linux-nfs@vger.kernel.org Date: Tue, 29 Apr 2025 09:54:29 -0700 In-Reply-To: <2526363b-1f4a-4999-9f9a-8c4c5c6c132d@oracle.com> References: <2526363b-1f4a-4999-9f9a-8c4c5c6c132d@oracle.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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trondmy@kernel.org wrote: > > From: Trond Myklebust > >=20 > > The Linux client assumes that all filehandles are non-volatile for > > renames within the same directory (otherwise sillyrename cannot work). > > However, the existence of the Linux 'subtree_check' export option has > > meant that nfs_rename() has always assumed it needs to flush writes > > before attempting to rename. > >=20 > > Since NFSv4 does allow the client to query whether or not the server > > exhibits this behaviour, and since knfsd does actually set the > > appropriate flag when 'subtree_check' is enabled on an export, it > > should be OK to optimise away the write flushing behaviour in the cases > > where it is clearly not needed. >=20 > No objection to the high level goal, seems like a sensible change. >=20 > So NFSv3 still has the flushing requirement, but NFSv4 can disable that > requirement as long as the server in question asserts FH4_VOLATILE_ANY > and FH4_VOL_RENAME, correct? >=20 (Note that there is a v2 patch that was posted soon after this) It's actually the reverse: if the server doesn't assert either FH4_VOL_RENAME or FH4_VOLATILE_ANY, then you're able to disable that requirement. > I'm wondering how confident we are that other server implementations > behave reasonably. Yes, they are broken if they don't behave, but there > is still risk of introducing a regression. > > Signed-off-by: Trond Myklebust > > --- > > fs/nfs/client.c | 2 ++ > > fs/nfs/dir.c | 15 ++++++++++++++- > > include/linux/nfs_fs_sb.h | 6 ++++++ > > 3 files changed, 22 insertions(+), 1 deletion(-) > >=20 > > diff --git a/fs/nfs/client.c b/fs/nfs/client.c > > index 2115c1189c2d..6d63b958c4bb 100644 > > --- a/fs/nfs/client.c > > +++ b/fs/nfs/client.c > > @@ -1105,6 +1105,8 @@ struct nfs_server *nfs_create_server(struct fs_co= ntext *fc) > > if (server->namelen =3D=3D 0 || server->namelen > NFS2_MAXNAMLEN) > > server->namelen =3D NFS2_MAXNAMLEN; > > } > > + /* Linux 'subtree_check' borkenness mandates this setting */ >=20 > Assuming you are going to respin this patch to deal with the build bot > warnings, can you make this comment more useful? "borkenness" sounds > like you are dealing with a server bug here, but that's not really > the case. subtree_check is working as designed: it requires the extra > flushing. The no_subtree_check case does not, IIUC. >=20 > It would be better to explain this need strictly in terms of file handle > volatility, no? >=20 >=20 > > + server->fh_expire_type =3D NFS_FH_VOL_RENAME; > > =20 > > if (!(fattr->valid & NFS_ATTR_FATTR)) { > > error =3D ctx->nfs_mod->rpc_ops->getattr(server, ctx->mntfh, > > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > > index bd23fc736b39..d0e0b435a843 100644 > > --- a/fs/nfs/dir.c > > +++ b/fs/nfs/dir.c > > @@ -2676,6 +2676,18 @@ nfs_unblock_rename(struct rpc_task *task, struct= nfs_renamedata *data) > > unblock_revalidate(new_dentry); > > } > > =20 > > +static bool nfs_rename_is_unsafe_cross_dir(struct dentry *old_dentry, > > + struct dentry *new_dentry) > > +{ > > + struct nfs_server *server =3D NFS_SB(old_dentry->d_sb); > > + > > + if (old_dentry->d_parent !=3D new_dentry->d_parent) > > + return false; > > + if (server->fh_expire_type & NFS_FH_RENAME_UNSAFE) > > + return !(server->fh_expire_type & NFS_FH_NOEXPIRE_WITH_OPEN); > > + return true; > > +} > > + > > /* > > * RENAME > > * FIXME: Some nfsds, like the Linux user space nfsd, may generate a > > @@ -2763,7 +2775,8 @@ int nfs_rename(struct mnt_idmap *idmap, struct in= ode *old_dir, > > =20 > > } > > =20 > > - if (S_ISREG(old_inode->i_mode)) > > + if (S_ISREG(old_inode->i_mode) && > > + nfs_rename_is_unsafe_cross_dir(old_dentry, new_dentry)) > > nfs_sync_inode(old_inode); > > task =3D nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry, > > must_unblock ? nfs_unblock_rename : NULL); > > diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h > > index 71319637a84e..6732c7e04d19 100644 > > --- a/include/linux/nfs_fs_sb.h > > +++ b/include/linux/nfs_fs_sb.h > > @@ -236,6 +236,12 @@ struct nfs_server { > > u32 acl_bitmask; /* V4 bitmask representing the ACEs > > that are supported on this > > filesystem */ > > + /* The following #defines numerically match the NFSv4 equivalents */ > > +#define NFS_FH_NOEXPIRE_WITH_OPEN (0x1) > > +#define NFS_FH_VOLATILE_ANY (0x2) > > +#define NFS_FH_VOL_MIGRATION (0x4) > > +#define NFS_FH_VOL_RENAME (0x8) > > +#define NFS_FH_RENAME_UNSAFE (NFS_FH_VOLATILE_ANY | NFS_FH_VOL_RENAME) > > u32 fh_expire_type; /* V4 bitmask representing file > > handle volatility type for > > this filesystem */ >=20 >=20 --=20 Jeff Layton