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From: Ira Weiny <ira.weiny@intel.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>,
	Dave Chinner <david@fromorbit.com>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Dan Williams <dan.j.williams@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	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: Sat, 4 Apr 2020 23:19:46 -0700
Message-ID: <20200405061945.GA94792@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200403183746.GQ80283@magnolia>

> > 
> > In summary:
> > 
> >  - Applications must call statx to discover the current S_DAX state.
> 
> Ok.
> 
> >  - There exists an advisory file inode flag FS_XFLAG_DAX that is set based on
> >    the parent directory FS_XFLAG_DAX inode flag.  (There is no way to change
> >    this flag after file creation.)
> > 
> >    If FS_XFLAG_DAX is set and the fs is on pmem then it will enable S_DAX at
> >    inode load time; if FS_XFLAG_DAX is not set, it will not enable S_DAX.
> >    Unless overridden...
> 
> Ok, fine with me. :)

:-D

> 
> >  - There exists a dax= mount option.
> > 
> >    "-o dax=off" means "never set S_DAX, ignore FS_XFLAG_DAX"
> >    	"-o nodax" means "dax=off"
> 
> I surveyed the three fses that support dax and found that none of the
> filesystems actually have a 'nodax' flag.  Now would be the time not to
> add such a thing, and make people specify dax=off instead.  It would
> be handy if we could have a single fsparam_enum for figuring out the dax
> mount options.

yes good point.

I'm working on updating the documentation patch and I think this might also
be better as:

	-o dax=never

Which is the opposite of 'always'.

> 
> >    "-o dax=always" means "always set S_DAX (at least on pmem), ignore FS_XFLAG_DAX"
> >    	"-o dax" by itself means "dax=always"
> >    "-o dax=iflag" means "follow FS_XFLAG_DAX" and is the default
> > 
> >  - There exists an advisory directory inode flag FS_XFLAG_DAX that can be
> >    changed at any time.  The flag state is copied into any files or
> >    subdirectories when they are created within that directory.  If programs
> >    require file access runs in S_DAX mode, they'll have to create those files
> 
> "...they must create..."

yes

> 
> >    inside a directory with FS_XFLAG_DAX set, or mount the fs with an
> >    appropriate dax mount option.
> 
> Otherwise seems ok to me.

Thanks!
Ira


  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
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 [this message]
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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