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From: Jan Kara <jack@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Dave Chinner <david@fromorbit.com>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH V5 00/12] Enable per-file/per-directory DAX operations V5
Date: Mon, 16 Mar 2020 10:52:24 +0100
Message-ID: <20200316095224.GF12783@quack2.suse.cz> (raw)
In-Reply-To: <CAPcyv4h9Xg61jk=Uq17xC6AGj9yOSAJnCaTzHcfBZwOVdRF9dw@mail.gmail.com>

On Wed 11-03-20 10:07:18, Dan Williams wrote:
> On Tue, Mar 10, 2020 at 11:30 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > On Tue, Mar 10, 2020 at 08:36:14PM -0700, Darrick J. Wong wrote:
> > > 1) Leave the inode flag (FS_XFLAG_DAX) as it is, and export the S_DAX
> > > status via statx.  Document that changes to FS_XFLAG_DAX do not take
> > > effect immediately and that one must check statx to find out the real
> > > mode.  If we choose this, I would also deprecate the dax mount option;
> > > send in my mkfs.xfs patch to make it so that you can set FS_XFLAG_DAX on
> > > all files at mkfs time; and we can finally lay this whole thing to rest.
> > > This is the closest to what we have today.
> > >
> > > 2) Withdraw FS_XFLAG_DAX entirely, and let the kernel choose based on
> > > usage patterns, hardware heuristics, or spiteful arbitrariness.
> >
> > 3) Only allow changing FS_XFLAG_DAX on directories or files that do
> > not have blocks allocated to them yet, and side step all the hard
> > problems.
> 
> This sounds reasonable to me.
> 
> As for deprecating the mount option, I think at a minimum it needs to
> continue be accepted as an option even if it is ignored to not break
> existing setups.

Agreed. But that's how we usually deprecate mount options. Also I'd say
that statx() support for reporting DAX state and some education of
programmers using DAX is required before we deprecate the mount option
since currently applications check 'dax' mount option to determine how much
memory they need to set aside for page cache before they consume everything
else on the machine...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-27  5:24 ira.weiny
2020-02-27  5:24 ` [PATCH V5 01/12] fs/xfs: Remove unnecessary initialization of i_rwsem ira.weiny
2020-02-27 17:25   ` Ira Weiny
2020-02-27  5:24 ` [PATCH V5 02/12] fs: Remove unneeded IS_DAX() check ira.weiny
2020-02-27  5:24 ` [PATCH V5 03/12] fs/stat: Define DAX statx attribute ira.weiny
2020-02-27  5:24 ` [PATCH V5 04/12] fs/xfs: Isolate the physical DAX flag from enabled ira.weiny
2020-02-27  5:24 ` [PATCH V5 05/12] fs/xfs: Create function xfs_inode_enable_dax() ira.weiny
2020-03-01 22:37   ` Dave Chinner
2020-02-27  5:24 ` [PATCH V5 06/12] fs: Add locking for a dynamic address space operations state ira.weiny
2020-03-02  1:26   ` Dave Chinner
2020-03-02  1:36     ` Dave Chinner
2020-02-27  5:24 ` [PATCH V5 07/12] fs: Prevent DAX state change if file is mmap'ed ira.weiny
2020-02-27  5:24 ` [PATCH V5 08/12] fs/xfs: Hold off aops users while changing DAX state ira.weiny
2020-02-27  5:24 ` [PATCH V5 09/12] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-02-27  5:24 ` [PATCH V5 10/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
2020-02-27  5:24 ` [PATCH V5 11/12] fs/xfs: Remove xfs_diflags_to_linux() ira.weiny
2020-02-27  5:24 ` [PATCH V5 12/12] Documentation/dax: Update Usage section ira.weiny
2020-03-05 15:51 ` [PATCH V5 00/12] Enable per-file/per-directory DAX operations V5 Christoph Hellwig
2020-03-09 17:04   ` Ira Weiny
2020-03-11  3:36     ` Darrick J. Wong
2020-03-11  6:29       ` Christoph Hellwig
2020-03-11 17:07         ` Dan Williams
2020-03-16  9:52           ` Jan Kara [this message]
2020-03-16  9:55             ` Christoph Hellwig
2020-04-01  4:00               ` Darrick J. Wong
2020-04-01 10:25                 ` Jan Kara
2020-04-02  8:53                   ` Christoph Hellwig
2020-04-02 20:55                     ` Ira Weiny
2020-04-03  7:27                       ` Christoph Hellwig
2020-04-03 15:48                         ` Ira Weiny
2020-04-03 17:03                           ` Jan Kara
2020-04-03 18:18                             ` Ira Weiny
2020-04-03 18:21                               ` Ira Weiny
2020-04-03 18:37                               ` Darrick J. Wong
2020-04-05  6:19                                 ` Ira Weiny
2020-04-06 10:00                               ` Jan Kara
2020-04-03 18:29                             ` Darrick J. Wong
2020-04-03 16:05                         ` Darrick J. Wong
2020-04-03  4:39                 ` Ira Weiny
2020-03-11  6:39       ` Dave Chinner
2020-03-11  6:44         ` Christoph Hellwig
2020-03-11 17:07           ` Dan Williams
2020-03-12  0:49           ` Dave Chinner
2020-03-12  3:00             ` Darrick J. Wong
2020-03-12  7:27             ` Christoph Hellwig

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