From: Dave Chinner <david@fromorbit.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
XFS Developers <xfs@oss.sgi.com>, Linux MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2 2/3] mm, dax: add VM_DAX flag for DAX VMAs
Date: Fri, 16 Sep 2016 11:24:59 +1000 [thread overview]
Message-ID: <20160916012458.GW22388@dastard> (raw)
In-Reply-To: <CAPcyv4jvcWEc2TkRh6-MoKb_-1VbFoiKUJEB=svQO+BVN8s-Sg@mail.gmail.com>
On Thu, Sep 15, 2016 at 05:16:42PM -0700, Dan Williams wrote:
> On Thu, Sep 15, 2016 at 4:07 PM, Dave Chinner <david@fromorbit.com> wrote:
> > On Thu, Sep 15, 2016 at 10:01:03AM -0700, Dan Williams wrote:
> >> 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?
> >
> > No, that's an admin flag, not a runtime hint for applications. Just
> > because that flag is set on an inode, it does not mean that DAX is
> > actually in use - it will be ignored if the backing dev is not dax
> > capable.
>
> What's the point of an admin flag if an admin can't do cat /proc/<pid
> of interest>/smaps, or some other mechanism, to validate that the
> setting the admin cares about is in effect?
Sorry, I don't follow - why would you be looking at mapping file
regions in /proc to determine if some file somewhere in a filesystem
has a specific flag set on it or not?
FS_XFLAG_DAX is an inode attribute flag, not something you can
query or administrate through mmap:
I.e.
# xfs_io -c "lsattr" -c "chattr +x" -c lsattr -c "chattr -x" -c "lsattr" foo
--------------- foo
--------------x foo
--------------- foo
#
What happens when that flag is set on an inode is determined by a
whole bunch of other things that are completely separate to the
management of the inode flag itself.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>, Linux MM <linux-mm@kvack.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
"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: Fri, 16 Sep 2016 11:24:59 +1000 [thread overview]
Message-ID: <20160916012458.GW22388@dastard> (raw)
In-Reply-To: <CAPcyv4jvcWEc2TkRh6-MoKb_-1VbFoiKUJEB=svQO+BVN8s-Sg@mail.gmail.com>
On Thu, Sep 15, 2016 at 05:16:42PM -0700, Dan Williams wrote:
> On Thu, Sep 15, 2016 at 4:07 PM, Dave Chinner <david@fromorbit.com> wrote:
> > On Thu, Sep 15, 2016 at 10:01:03AM -0700, Dan Williams wrote:
> >> 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?
> >
> > No, that's an admin flag, not a runtime hint for applications. Just
> > because that flag is set on an inode, it does not mean that DAX is
> > actually in use - it will be ignored if the backing dev is not dax
> > capable.
>
> What's the point of an admin flag if an admin can't do cat /proc/<pid
> of interest>/smaps, or some other mechanism, to validate that the
> setting the admin cares about is in effect?
Sorry, I don't follow - why would you be looking at mapping file
regions in /proc to determine if some file somewhere in a filesystem
has a specific flag set on it or not?
FS_XFLAG_DAX is an inode attribute flag, not something you can
query or administrate through mmap:
I.e.
# xfs_io -c "lsattr" -c "chattr +x" -c lsattr -c "chattr -x" -c "lsattr" foo
--------------- foo
--------------x foo
--------------- foo
#
What happens when that flag is set on an inode is determined by a
whole bunch of other things that are completely separate to the
management of the inode flag itself.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>, Linux MM <linux-mm@kvack.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"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: Fri, 16 Sep 2016 11:24:59 +1000 [thread overview]
Message-ID: <20160916012458.GW22388@dastard> (raw)
In-Reply-To: <CAPcyv4jvcWEc2TkRh6-MoKb_-1VbFoiKUJEB=svQO+BVN8s-Sg@mail.gmail.com>
On Thu, Sep 15, 2016 at 05:16:42PM -0700, Dan Williams wrote:
> On Thu, Sep 15, 2016 at 4:07 PM, Dave Chinner <david@fromorbit.com> wrote:
> > On Thu, Sep 15, 2016 at 10:01:03AM -0700, Dan Williams wrote:
> >> 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?
> >
> > No, that's an admin flag, not a runtime hint for applications. Just
> > because that flag is set on an inode, it does not mean that DAX is
> > actually in use - it will be ignored if the backing dev is not dax
> > capable.
>
> What's the point of an admin flag if an admin can't do cat /proc/<pid
> of interest>/smaps, or some other mechanism, to validate that the
> setting the admin cares about is in effect?
Sorry, I don't follow - why would you be looking at mapping file
regions in /proc to determine if some file somewhere in a filesystem
has a specific flag set on it or not?
FS_XFLAG_DAX is an inode attribute flag, not something you can
query or administrate through mmap:
I.e.
# xfs_io -c "lsattr" -c "chattr +x" -c lsattr -c "chattr -x" -c "lsattr" foo
--------------- foo
--------------x foo
--------------- foo
#
What happens when that flag is set on an inode is determined by a
whole bunch of other things that are completely separate to the
management of the inode flag itself.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
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>
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
XFS Developers <xfs@oss.sgi.com>, Linux MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2 2/3] mm, dax: add VM_DAX flag for DAX VMAs
Date: Fri, 16 Sep 2016 11:24:59 +1000 [thread overview]
Message-ID: <20160916012458.GW22388@dastard> (raw)
In-Reply-To: <CAPcyv4jvcWEc2TkRh6-MoKb_-1VbFoiKUJEB=svQO+BVN8s-Sg@mail.gmail.com>
On Thu, Sep 15, 2016 at 05:16:42PM -0700, Dan Williams wrote:
> On Thu, Sep 15, 2016 at 4:07 PM, Dave Chinner <david@fromorbit.com> wrote:
> > On Thu, Sep 15, 2016 at 10:01:03AM -0700, Dan Williams wrote:
> >> 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?
> >
> > No, that's an admin flag, not a runtime hint for applications. Just
> > because that flag is set on an inode, it does not mean that DAX is
> > actually in use - it will be ignored if the backing dev is not dax
> > capable.
>
> What's the point of an admin flag if an admin can't do cat /proc/<pid
> of interest>/smaps, or some other mechanism, to validate that the
> setting the admin cares about is in effect?
Sorry, I don't follow - why would you be looking at mapping file
regions in /proc to determine if some file somewhere in a filesystem
has a specific flag set on it or not?
FS_XFLAG_DAX is an inode attribute flag, not something you can
query or administrate through mmap:
I.e.
# xfs_io -c "lsattr" -c "chattr +x" -c lsattr -c "chattr -x" -c "lsattr" foo
--------------- foo
--------------x foo
--------------- foo
#
What happens when that flag is set on an inode is determined by a
whole bunch of other things that are completely separate to the
management of the inode flag itself.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2016-09-16 1:25 UTC|newest]
Thread overview: 63+ 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 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
2016-09-15 6:54 ` 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 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
2016-09-15 6:54 ` 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 6:54 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
2016-09-15 8:26 ` Christoph Hellwig
2016-09-15 8:26 ` Christoph Hellwig
2016-09-15 8:26 ` Christoph Hellwig
2016-09-15 17:01 ` Dan Williams
2016-09-15 17:01 ` Dan Williams
2016-09-15 17:01 ` Dan Williams
2016-09-15 17:01 ` Dan Williams
2016-09-15 17:09 ` Darrick J. Wong
2016-09-15 17:09 ` Darrick J. Wong
2016-09-15 17:09 ` Darrick J. Wong
2016-09-15 17:09 ` Darrick J. Wong
2016-09-15 17:44 ` Dan Williams
2016-09-15 17:44 ` Dan Williams
2016-09-15 17:44 ` Dan Williams
2016-09-15 17:44 ` Dan Williams
2016-09-15 23:07 ` Dave Chinner
2016-09-15 23:07 ` Dave Chinner
2016-09-15 23:07 ` Dave Chinner
2016-09-15 23:07 ` Dave Chinner
2016-09-15 23:19 ` Dan Williams
2016-09-15 23:19 ` Dan Williams
2016-09-15 23:19 ` Dan Williams
2016-09-15 23:19 ` Dan Williams
2016-09-16 0:16 ` Dan Williams
2016-09-16 0:16 ` Dan Williams
2016-09-16 0:16 ` Dan Williams
2016-09-16 0:16 ` Dan Williams
2016-09-16 1:24 ` Dave Chinner [this message]
2016-09-16 1:24 ` Dave Chinner
2016-09-16 1:24 ` Dave Chinner
2016-09-16 1:24 ` Dave Chinner
2016-09-16 2:04 ` Dan Williams
2016-09-16 2:04 ` Dan Williams
2016-09-16 2:04 ` Dan Williams
2016-09-16 2:04 ` Dan Williams
2016-09-16 3:41 ` Dan Williams
2016-09-16 3:41 ` Dan Williams
2016-09-16 3:41 ` Dan Williams
2016-09-16 3:41 ` Dan Williams
2016-09-16 5:36 ` Dave Chinner
2016-09-16 5:36 ` Dave Chinner
2016-09-16 5:36 ` Dave Chinner
2016-09-16 5:36 ` Dave Chinner
2016-09-16 10:47 ` Dan Williams
2016-09-16 10:47 ` Dan Williams
2016-09-16 10:47 ` Dan Williams
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
2016-09-15 6:54 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
2016-09-15 6:54 ` Dan Williams
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