From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: Re: [PATCH RESEND] ubifs: Introduce a mount option of force_atime. Date: Fri, 26 Jun 2015 10:01:23 +0300 Message-ID: <1435302083.9627.36.camel@sauron.fi.intel.com> References: <1433831809.28854.17.camel@sauron.fi.intel.com> <55769D97.3010602@nod.at> <5577AC03.9060909@cn.fujitsu.com> <1433928078.14092.1.camel@sauron.fi.intel.com> <55780D1C.6080907@cn.fujitsu.com> <1433931934.14092.11.camel@sauron.fi.intel.com> <557812A4.8020409@cn.fujitsu.com> <1433934324.14092.15.camel@sauron.fi.intel.com> <55892D18.3020203@cn.fujitsu.com> <1435056240.7659.69.camel@sauron.fi.intel.com> <20150624003335.GG22807@dastard> <558BD010.6020207@cn.fujitsu.com> <1435226918.9627.14.camel@sauron.fi.intel.com> <558BD3B0.8080209@cn.fujitsu.com> <1435231689.9627.17.camel@sauron.fi.intel.com> <558CA82B.7050306@cn.fujitsu.com> Reply-To: dedekind1@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Dave Chinner , Richard Weinberger , linux-mtd@lists.infradead.org, adrian.hunter@intel.com, linux-fsdevel@vger.kernel.org To: Dongsheng Yang Return-path: Received: from mga11.intel.com ([192.55.52.93]:58516 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751558AbbFZHB2 (ORCPT ); Fri, 26 Jun 2015 03:01:28 -0400 In-Reply-To: <558CA82B.7050306@cn.fujitsu.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, 2015-06-26 at 09:17 +0800, Dongsheng Yang wrote: > On 06/25/2015 07:28 PM, Artem Bityutskiy wrote: > > On Thu, 2015-06-25 at 18:10 +0800, Dongsheng Yang wrote: > >> > -o - default behavior (no atime) > >> > -o relatime - relative atime support > >> > >> We would find both of them are MS_RELATIME set. But we > >> want to do different thing in these cases. So I introduced > >> the force_atime. Then: > > > > Oh, do you know where exactly the default MS_RELATIME gets set? > > Ha, yes, it was set in do_mount() in vfs. I mentioned this in a mail > days ago, but let me try to explain it more clearly here. OK, right, I see it: commit 0a1c01c9477602ee8b44548a9405b2c1d587b5a2 Author: Matthew Garrett Date: Thu Mar 26 17:53:14 2009 +0000 Make relatime default Change the default behaviour of the kernel to use relatime for all filesystems. This can be overridden with the "strictatime" mount option. Signed-off-by: Matthew Garrett Signed-off-by: Linus Torvalds diff --git a/fs/namespace.c b/fs/namespace.c index d0659ec..f0e7530 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1920,6 +1920,9 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, if (data_page) ((char *)data_page)[PAGE_SIZE - 1] = 0; + /* Default to relatime */ + mnt_flags |= MNT_RELATIME; + /* Separate the per-mountpoint flags */ if (flags & MS_NOSUID) mnt_flags |= MNT_NOSUID; @@ -1931,8 +1934,6 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, mnt_flags |= MNT_NOATIME; if (flags & MS_NODIRATIME) mnt_flags |= MNT_NODIRATIME; - if (flags & MS_RELATIME) - mnt_flags |= MNT_RELATIME; if (flags & MS_STRICTATIME) mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); if (flags & MS_RDONLY) This means that if a file-system (e.g., UBIFS or JFFS2) never supported atime, it is harder to add atime support without breaking the old behavior. What if we push the two "set NOATIME flag" lines of code down to individual file-systems, instead of having it at the VFS level? ... snip ... > (d), But when I heard an idea about UBIFS_ATIME_SUPPORT from you. > I get an idea 3. > ======================idea 3 in ubifs========================= > UBIFS_ATIME_SUPPORT is n, same with what ubifs did: > -o - no atime > -o atime - no atime > -o noatime - no atime > -o relatime - no atime > -o strictatime - no atime > -o lazyatime - no atime > > UBIFS_ATIME_SUPPORT is y, same with what generic is doing: > -o - default behavior (relatime currently) > -o atime - atime support > -o noatime - no atime support > -o relatime - relative atime support > -o strictatime - strict atime support > -o lazyatime - lazy atime support Yes, this is an option, I am just trying to explore other possibilities.