From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Linux MM <linux-mm@kvack.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
david <david@fromorbit.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
XFS Developers <xfs@oss.sgi.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 2/3] mm, dax: add VM_DAX flag for DAX VMAs
Date: Thu, 15 Sep 2016 10:01:03 -0700 [thread overview]
Message-ID: <CAPcyv4jTw3cXpmmJRh7t16Xy2uYofDe+fJ+X_jnz+Q=o0uGneg@mail.gmail.com> (raw)
In-Reply-To: <20160915082615.GA9772@lst.de>
On Thu, Sep 15, 2016 at 1:26 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Wed, Sep 14, 2016 at 11:54:38PM -0700, Dan Williams wrote:
>> The DAX property, page cache bypass, of a VMA is only detectable via the
>> vma_is_dax() helper to check the S_DAX inode flag. However, this is
>> only available internal to the kernel and is a property that userspace
>> applications would like to interrogate.
>
> They have absolutely no business knowing such an implementation detail.
Hasn't that train already left the station with FS_XFLAG_DAX?
The other problem with hiding the DAX property is that it turns out to
not be a transparent acceleration feature. See xfs/086 xfs/088
xfs/089 xfs/091 which fail with DAX and, as far as I understand, it is
due to the fact that DAX disallows delayed allocation behavior.
If behavior changes I think we should indicate that to userspace and
VM_DAX is certainly more useful to userspace than some of the other vm
internals we already export in those flags.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-09-15 17:01 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-15 6:54 [PATCH v2 0/3] mm, dax: export dax capabilities and mapping size info to userspace Dan Williams
2016-09-15 6:54 ` [PATCH v2 1/3] mm, dax: add VM_SYNC flag for device-dax VMAs Dan Williams
2016-09-15 6:54 ` [PATCH v2 2/3] mm, dax: add VM_DAX flag for DAX VMAs Dan Williams
2016-09-15 8:26 ` Christoph Hellwig
2016-09-15 17:01 ` Dan Williams [this message]
2016-09-15 17:09 ` Darrick J. Wong
2016-09-15 17:44 ` Dan Williams
2016-09-15 23:07 ` Dave Chinner
2016-09-15 23:19 ` Dan Williams
2016-09-16 0:16 ` Dan Williams
2016-09-16 1:24 ` Dave Chinner
2016-09-16 2:04 ` Dan Williams
2016-09-16 3:41 ` Dan Williams
2016-09-16 5:36 ` Dave Chinner
2016-09-16 10:47 ` Dan Williams
2016-09-15 6:54 ` [PATCH v2 3/3] mm, mincore2(): retrieve tlb-size attributes of an address range Dan Williams
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPcyv4jTw3cXpmmJRh7t16Xy2uYofDe+fJ+X_jnz+Q=o0uGneg@mail.gmail.com' \
--to=dan.j.williams@intel.com \
--cc=david@fromorbit.com \
--cc=hch@lst.de \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nvdimm@lists.01.org \
--cc=npiggin@gmail.com \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox