From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Ira Weiny <ira.weiny@intel.com>, Jan Kara <jack@suse.cz>,
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: Fri, 3 Apr 2020 09:05:44 -0700 [thread overview]
Message-ID: <20200403160544.GO80283@magnolia> (raw)
In-Reply-To: <20200403072731.GA24176@lst.de>
On Fri, Apr 03, 2020 at 09:27:31AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 02, 2020 at 01:55:19PM -0700, Ira Weiny wrote:
> > > 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.
>
> I really, really dislike that idea. The whole point of not forcing
> evictions is to make it clear - no this inode is "busy" you can't
> do that. A reasonably smart application can try to evict itself.
>
> But returning an error and doing a lazy change anyway is straight from
> the playbook for arcane and confusing API designs.
Agreed. That's why I wrote that applications can set FS_XFLAG_DAX and
then query statx for STATX_ATTR_DAX to find out if it actually took
effect, and that if applications require it immediately they can either
create a file in a FS_XFLAG_DAX directory, or the admin can mount with
dax=always. No magic return values required or desired anywhere.
I don't know what "try to evict the inode" magic means, but I'm fairly
sure I don't want to. ;)
--D
next prev parent reply other threads:[~2020-04-03 16:06 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-27 5:24 [PATCH V5 00/12] Enable per-file/per-directory DAX operations V5 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
2020-04-06 10:00 ` Jan Kara
2020-04-03 18:29 ` Darrick J. Wong
2020-04-03 16:05 ` Darrick J. Wong [this message]
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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