From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57F70C388F9 for ; Sat, 21 Nov 2020 13:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0777D2224A for ; Sat, 21 Nov 2020 13:00:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="rcb4uvhe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727274AbgKUNAe (ORCPT ); Sat, 21 Nov 2020 08:00:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:49684 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727677AbgKUNAd (ORCPT ); Sat, 21 Nov 2020 08:00:33 -0500 Received: from tleilax.poochiereds.net (68-20-15-154.lightspeed.rlghnc.sbcglobal.net [68.20.15.154]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E5771217A0; Sat, 21 Nov 2020 13:00:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605963632; bh=bWO4512rrwQksK0Rvo197S83Z8f0AoILWgXDmivlrV4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=rcb4uvhe6Kx3DPlF3dU2gkn8SeGGCSRmVm6JxtlNpe/nDVZun/LjR3NtE8lZ5PeKo bKHKBdGyIJ22edC3AZVzlukekMT9SPxxbh6IidiIqr3IgQiyH5v9eeIp43BINEiFdZ G27VXIvr2CZWLMz7leO7LRFJvrw7F0Cr1ysObE4U= Message-ID: <8462cb90445a8553d0667e6ca59fbb42835ad9a9.camel@kernel.org> Subject: Re: [PATCH 6/8] nfsd: move change attribute generation to filesystem From: Jeff Layton To: "J. Bruce Fields" Cc: Daire Byrne , Trond Myklebust , linux-cachefs , linux-nfs Date: Sat, 21 Nov 2020 08:00:30 -0500 In-Reply-To: <1605911960-12516-6-git-send-email-bfields@redhat.com> References: <20201120223831.GB7705@fieldses.org> <1605911960-12516-1-git-send-email-bfields@redhat.com> <1605911960-12516-6-git-send-email-bfields@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.1 (3.38.1-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, 2020-11-20 at 17:39 -0500, J. Bruce Fields wrote: > From: "J. Bruce Fields" > > After this, only filesystems lacking change attribute support will leave > the fetch_iversion export op NULL. > > This seems cleaner to me, and will allow some minor optimizations in the > nfsd code. > > Signed-off-by: J. Bruce Fields > --- >  fs/btrfs/export.c | 2 ++ >  fs/ext4/super.c | 9 +++++++++ >  fs/nfsd/nfs4xdr.c | 2 +- >  fs/nfsd/nfsfh.h | 25 +++---------------------- >  fs/nfsd/xdr4.h | 4 +++- >  fs/xfs/xfs_export.c | 2 ++ >  include/linux/iversion.h | 26 ++++++++++++++++++++++++++ >  7 files changed, 46 insertions(+), 24 deletions(-) > > diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c > index 1a8d419d9e1f..ece32440999a 100644 > --- a/fs/btrfs/export.c > +++ b/fs/btrfs/export.c > @@ -7,6 +7,7 @@ >  #include "btrfs_inode.h" >  #include "print-tree.h" >  #include "export.h" > +#include >   > >  #define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \ >   parent_objectid) / 4) > @@ -279,4 +280,5 @@ const struct export_operations btrfs_export_ops = { >   .fh_to_parent = btrfs_fh_to_parent, >   .get_parent = btrfs_get_parent, >   .get_name = btrfs_get_name, > + .fetch_iversion = generic_fetch_iversion, >  }; > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index ef4734b40e2a..a4f48273d435 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -1685,11 +1685,20 @@ static const struct super_operations ext4_sops = { >   .bdev_try_to_free_page = bdev_try_to_free_page, >  }; >   > > +static u64 ext4_fetch_iversion(struct inode *inode) > +{ > + if (IS_I_VERSION(inode)) > + return generic_fetch_iversion(inode); > + else > + return time_to_chattr(&inode->i_ctime); > +} > + >  static const struct export_operations ext4_export_ops = { >   .fh_to_dentry = ext4_fh_to_dentry, >   .fh_to_parent = ext4_fh_to_parent, >   .get_parent = ext4_get_parent, >   .commit_metadata = ext4_nfs_commit_metadata, > + .fetch_iversion = ext4_fetch_iversion, >  }; >   > >  enum { > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c > index 18c912930947..182190684792 100644 > --- a/fs/nfsd/nfs4xdr.c > +++ b/fs/nfsd/nfs4xdr.c > @@ -3187,7 +3187,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, >   p = xdr_reserve_space(xdr, 4); >   if (!p) >   goto out_resource; > - if (IS_I_VERSION(d_inode(dentry))) > + if (IS_I_VERSION(d_inode(dentry)) >   *p++ = cpu_to_be32(NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR); >   else >   *p++ = cpu_to_be32(NFS4_CHANGE_TYPE_IS_TIME_METADATA); > diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h > index 2656a3464c6c..ac3e309d7339 100644 > --- a/fs/nfsd/nfsfh.h > +++ b/fs/nfsd/nfsfh.h > @@ -46,8 +46,8 @@ typedef struct svc_fh { >   struct timespec64 fh_pre_mtime; /* mtime before oper */ >   struct timespec64 fh_pre_ctime; /* ctime before oper */ >   /* > - * pre-op nfsv4 change attr: note must check IS_I_VERSION(inode) > - * to find out if it is valid. > + * pre-op nfsv4 change attr: note must check for fetch_iversion > + * op to find out if it is valid. >   */ >   u64 fh_pre_change; >   > > @@ -246,31 +246,12 @@ fh_clear_wcc(struct svc_fh *fhp) >   fhp->fh_pre_saved = false; >  } >   > > -/* > - * We could use i_version alone as the change attribute. However, > - * i_version can go backwards after a reboot. On its own that doesn't > - * necessarily cause a problem, but if i_version goes backwards and then > - * is incremented again it could reuse a value that was previously used > - * before boot, and a client who queried the two values might > - * incorrectly assume nothing changed. > - * > - * By using both ctime and the i_version counter we guarantee that as > - * long as time doesn't go backwards we never reuse an old value. > - */ >  static inline u64 nfsd4_change_attribute(struct kstat *stat, >   struct inode *inode) >  { >   if (inode->i_sb->s_export_op->fetch_iversion) >   return inode->i_sb->s_export_op->fetch_iversion(inode); > - else if (IS_I_VERSION(inode)) { > - u64 chattr; > - > - chattr = stat->ctime.tv_sec; > - chattr <<= 30; > - chattr += stat->ctime.tv_nsec; > - chattr += inode_query_iversion(inode); > - return chattr; > - } else > + else >   return time_to_chattr(&stat->ctime); >  } >   > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > index 9c2d942d055d..f0c8fbe704a2 100644 > --- a/fs/nfsd/xdr4.h > +++ b/fs/nfsd/xdr4.h > @@ -761,10 +761,12 @@ void warn_on_nonidempotent_op(struct nfsd4_op *op); >  static inline void >  set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp) >  { > + struct inode *inode = d_inode(fhp->fh_dentry); > + >   BUG_ON(!fhp->fh_pre_saved); >   cinfo->atomic = (u32)fhp->fh_post_saved; >   > > - if (IS_I_VERSION(d_inode(fhp->fh_dentry))) { > + if (inode->i_sb->s_export_op->fetch_iversion) { >   cinfo->before_change = fhp->fh_pre_change; >   cinfo->after_change = fhp->fh_post_change; >   } else { > diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c > index 465fd9e048d4..b950fac3d7df 100644 > --- a/fs/xfs/xfs_export.c > +++ b/fs/xfs/xfs_export.c > @@ -16,6 +16,7 @@ >  #include "xfs_inode_item.h" >  #include "xfs_icache.h" >  #include "xfs_pnfs.h" > +#include >   > >  /* >   * Note that we only accept fileids which are long enough rather than allow > @@ -234,4 +235,5 @@ const struct export_operations xfs_export_operations = { >   .map_blocks = xfs_fs_map_blocks, >   .commit_blocks = xfs_fs_commit_blocks, >  #endif > + .fetch_iversion = generic_fetch_iversion, >  }; > diff --git a/include/linux/iversion.h b/include/linux/iversion.h > index 3bfebde5a1a6..ded74523c8a6 100644 > --- a/include/linux/iversion.h > +++ b/include/linux/iversion.h > @@ -328,6 +328,32 @@ inode_query_iversion(struct inode *inode) >   return cur >> I_VERSION_QUERIED_SHIFT; >  } >   > > +/* > + * We could use i_version alone as the NFSv4 change attribute. However, > + * i_version can go backwards after a reboot. On its own that doesn't > + * necessarily cause a problem, but if i_version goes backwards and then > + * is incremented again it could reuse a value that was previously used > + * before boot, and a client who queried the two values might > + * incorrectly assume nothing changed. > + * > + * By using both ctime and the i_version counter we guarantee that as > + * long as time doesn't go backwards we never reuse an old value. > + * > + * A filesystem that has an on-disk boot counter or similar might prefer > + * to use that to avoid the risk of the change attribute going backwards > + * if system time is set backwards. > + */ > +static inline u64 generic_fetch_iversion(struct inode *inode) > +{ > + u64 chattr; > + > + chattr = inode->i_ctime.tv_sec; > + chattr <<= 30; > + chattr += inode->i_ctime.tv_nsec; > + chattr += inode_query_iversion(inode); > + return chattr; > +} > + >  /* >   * For filesystems without any sort of change attribute, the best we can >   * do is fake one up from the ctime: One more nit: We probably don't want anyone using this on filesystems that don't set SB_I_VERSION. It might be a good idea to add something like: WARN_ON_ONCE(!IS_I_VERSION(inode)); To this function, to catch anyone trying to do it. -- Jeff Layton