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From: Ira Weiny <ira.weiny@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	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: Thu, 2 Apr 2020 13:55:19 -0700
Message-ID: <20200402205518.GF3952565@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200402085327.GA19109@lst.de>

On Thu, Apr 02, 2020 at 10:53:27AM +0200, Christoph Hellwig wrote:
> On Wed, Apr 01, 2020 at 12:25:11PM +0200, Jan Kara wrote:
> > >  - Applications must call statx to discover the current S_DAX state.
> > > 
> > >  - There exists an advisory file inode flag FS_XFLAG_DAX that can be
> > >    changed on files that have no blocks allocated to them.  Changing
> > >    this flag does not necessarily change the S_DAX state immediately
> > >    but programs can query the S_DAX state via statx.
> > 
> > I generally like the proposal but I think the fact that toggling
> > FS_XFLAG_DAX will not have immediate effect on S_DAX will cause quite some
> > confusion and ultimately bug reports. I'm thinking whether we could somehow
> > improve this... For example an ioctl that would try to make set inode flags
> > effective by evicting the inode (and returning EBUSY if the eviction is
> > impossible for some reason)?
> 
> I'd just return an error for that case, don't play silly games like
> evicting the inode.

I think I agree with Christoph here.  But I want to clarify.  I was heading in
a direction of failing the ioctl completely.  But we could have the flag change
with an appropriate error which could let the user know the change has been
delayed.

But I don't immediately see what error code is appropriate for such an
indication.  Candidates I can envision:

EAGAIN
ERESTART
EUSERS
EINPROGRESS

None are perfect but I'm leaning toward EINPROGRESS.

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 [this message]
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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