From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@lst.de>,
linux-xfs@vger.kernel.org, linux-mm@kvack.org,
Andreas Dilger <adilger.kernel@dilger.ca>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.com>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 04/11] ext2: remove support for DAX PMD faults
Date: Wed, 28 Sep 2016 12:46:43 -0600 [thread overview]
Message-ID: <20160928184643.GA16000@linux.intel.com> (raw)
In-Reply-To: <20160927214720.GD27872@dastard>
On Wed, Sep 28, 2016 at 07:47:20AM +1000, Dave Chinner wrote:
> On Tue, Sep 27, 2016 at 02:47:55PM -0600, Ross Zwisler wrote:
> > DAX PMD support was added via the following commit:
> >
> > commit e7b1ea2ad658 ("ext2: huge page fault support")
> >
> > I believe this path to be untested as ext2 doesn't reliably provide block
> > allocations that are aligned to 2MiB. In my testing I've been unable to
> > get ext2 to actually fault in a PMD. It always fails with a "pfn
> > unaligned" message because the sector returned by ext2_get_block() isn't
> > aligned.
> >
> > I've tried various settings for the "stride" and "stripe_width" extended
> > options to mkfs.ext2, without any luck.
> >
> > Since we can't reliably get PMDs, remove support so that we don't have an
> > untested code path that we may someday traverse when we happen to get an
> > aligned block allocation. This should also make 4k DAX faults in ext2 a
> > bit faster since they will no longer have to call the PMD fault handler
> > only to get a response of VM_FAULT_FALLBACK.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ....
> > @@ -154,7 +133,6 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >
> > static const struct vm_operations_struct ext2_dax_vm_ops = {
> > .fault = ext2_dax_fault,
> > - .pmd_fault = ext2_dax_pmd_fault,
> > .page_mkwrite = ext2_dax_fault,
> > .pfn_mkwrite = ext2_dax_pfn_mkwrite,
> > };
>
> Would it be better to put a comment mentioning this here? So as the
> years go by, this reminds people not to bother trying to implement
> it?
>
> /*
> * .pmd_fault is not supported for DAX because allocation in ext2
> * cannot be reliably aligned to huge page sizes and so pmd faults
> * will always fail and fail back to regular faults.
> */
Sure, this seems like a good idea. I'll add it, thanks.
_______________________________________________
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: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-kernel@vger.kernel.org, "Theodore Ts'o" <tytso@mit.edu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-nvdimm@ml01.01.org,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH v3 04/11] ext2: remove support for DAX PMD faults
Date: Wed, 28 Sep 2016 12:46:43 -0600 [thread overview]
Message-ID: <20160928184643.GA16000@linux.intel.com> (raw)
In-Reply-To: <20160927214720.GD27872@dastard>
On Wed, Sep 28, 2016 at 07:47:20AM +1000, Dave Chinner wrote:
> On Tue, Sep 27, 2016 at 02:47:55PM -0600, Ross Zwisler wrote:
> > DAX PMD support was added via the following commit:
> >
> > commit e7b1ea2ad658 ("ext2: huge page fault support")
> >
> > I believe this path to be untested as ext2 doesn't reliably provide block
> > allocations that are aligned to 2MiB. In my testing I've been unable to
> > get ext2 to actually fault in a PMD. It always fails with a "pfn
> > unaligned" message because the sector returned by ext2_get_block() isn't
> > aligned.
> >
> > I've tried various settings for the "stride" and "stripe_width" extended
> > options to mkfs.ext2, without any luck.
> >
> > Since we can't reliably get PMDs, remove support so that we don't have an
> > untested code path that we may someday traverse when we happen to get an
> > aligned block allocation. This should also make 4k DAX faults in ext2 a
> > bit faster since they will no longer have to call the PMD fault handler
> > only to get a response of VM_FAULT_FALLBACK.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ....
> > @@ -154,7 +133,6 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >
> > static const struct vm_operations_struct ext2_dax_vm_ops = {
> > .fault = ext2_dax_fault,
> > - .pmd_fault = ext2_dax_pmd_fault,
> > .page_mkwrite = ext2_dax_fault,
> > .pfn_mkwrite = ext2_dax_pfn_mkwrite,
> > };
>
> Would it be better to put a comment mentioning this here? So as the
> years go by, this reminds people not to bother trying to implement
> it?
>
> /*
> * .pmd_fault is not supported for DAX because allocation in ext2
> * cannot be reliably aligned to huge page sizes and so pmd faults
> * will always fail and fail back to regular faults.
> */
Sure, this seems like a good idea. I'll add it, thanks.
WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-kernel@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-nvdimm@lists.01.org,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH v3 04/11] ext2: remove support for DAX PMD faults
Date: Wed, 28 Sep 2016 12:46:43 -0600 [thread overview]
Message-ID: <20160928184643.GA16000@linux.intel.com> (raw)
In-Reply-To: <20160927214720.GD27872@dastard>
On Wed, Sep 28, 2016 at 07:47:20AM +1000, Dave Chinner wrote:
> On Tue, Sep 27, 2016 at 02:47:55PM -0600, Ross Zwisler wrote:
> > DAX PMD support was added via the following commit:
> >
> > commit e7b1ea2ad658 ("ext2: huge page fault support")
> >
> > I believe this path to be untested as ext2 doesn't reliably provide block
> > allocations that are aligned to 2MiB. In my testing I've been unable to
> > get ext2 to actually fault in a PMD. It always fails with a "pfn
> > unaligned" message because the sector returned by ext2_get_block() isn't
> > aligned.
> >
> > I've tried various settings for the "stride" and "stripe_width" extended
> > options to mkfs.ext2, without any luck.
> >
> > Since we can't reliably get PMDs, remove support so that we don't have an
> > untested code path that we may someday traverse when we happen to get an
> > aligned block allocation. This should also make 4k DAX faults in ext2 a
> > bit faster since they will no longer have to call the PMD fault handler
> > only to get a response of VM_FAULT_FALLBACK.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ....
> > @@ -154,7 +133,6 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >
> > static const struct vm_operations_struct ext2_dax_vm_ops = {
> > .fault = ext2_dax_fault,
> > - .pmd_fault = ext2_dax_pmd_fault,
> > .page_mkwrite = ext2_dax_fault,
> > .pfn_mkwrite = ext2_dax_pfn_mkwrite,
> > };
>
> Would it be better to put a comment mentioning this here? So as the
> years go by, this reminds people not to bother trying to implement
> it?
>
> /*
> * .pmd_fault is not supported for DAX because allocation in ext2
> * cannot be reliably aligned to huge page sizes and so pmd faults
> * will always fail and fail back to regular faults.
> */
Sure, this seems like a good idea. I'll add it, thanks.
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WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
To: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
Cc: Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>,
Matthew Wilcox <mawilcox-0li6OtcxBFHby3iVrkZq2A@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>,
linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Andreas Dilger
<adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org>,
Alexander Viro
<viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH v3 04/11] ext2: remove support for DAX PMD faults
Date: Wed, 28 Sep 2016 12:46:43 -0600 [thread overview]
Message-ID: <20160928184643.GA16000@linux.intel.com> (raw)
In-Reply-To: <20160927214720.GD27872@dastard>
On Wed, Sep 28, 2016 at 07:47:20AM +1000, Dave Chinner wrote:
> On Tue, Sep 27, 2016 at 02:47:55PM -0600, Ross Zwisler wrote:
> > DAX PMD support was added via the following commit:
> >
> > commit e7b1ea2ad658 ("ext2: huge page fault support")
> >
> > I believe this path to be untested as ext2 doesn't reliably provide block
> > allocations that are aligned to 2MiB. In my testing I've been unable to
> > get ext2 to actually fault in a PMD. It always fails with a "pfn
> > unaligned" message because the sector returned by ext2_get_block() isn't
> > aligned.
> >
> > I've tried various settings for the "stride" and "stripe_width" extended
> > options to mkfs.ext2, without any luck.
> >
> > Since we can't reliably get PMDs, remove support so that we don't have an
> > untested code path that we may someday traverse when we happen to get an
> > aligned block allocation. This should also make 4k DAX faults in ext2 a
> > bit faster since they will no longer have to call the PMD fault handler
> > only to get a response of VM_FAULT_FALLBACK.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> ....
> > @@ -154,7 +133,6 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >
> > static const struct vm_operations_struct ext2_dax_vm_ops = {
> > .fault = ext2_dax_fault,
> > - .pmd_fault = ext2_dax_pmd_fault,
> > .page_mkwrite = ext2_dax_fault,
> > .pfn_mkwrite = ext2_dax_pfn_mkwrite,
> > };
>
> Would it be better to put a comment mentioning this here? So as the
> years go by, this reminds people not to bother trying to implement
> it?
>
> /*
> * .pmd_fault is not supported for DAX because allocation in ext2
> * cannot be reliably aligned to huge page sizes and so pmd faults
> * will always fail and fail back to regular faults.
> */
Sure, this seems like a good idea. I'll add it, thanks.
WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-kernel@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-nvdimm@lists.01.org,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH v3 04/11] ext2: remove support for DAX PMD faults
Date: Wed, 28 Sep 2016 12:46:43 -0600 [thread overview]
Message-ID: <20160928184643.GA16000@linux.intel.com> (raw)
In-Reply-To: <20160927214720.GD27872@dastard>
On Wed, Sep 28, 2016 at 07:47:20AM +1000, Dave Chinner wrote:
> On Tue, Sep 27, 2016 at 02:47:55PM -0600, Ross Zwisler wrote:
> > DAX PMD support was added via the following commit:
> >
> > commit e7b1ea2ad658 ("ext2: huge page fault support")
> >
> > I believe this path to be untested as ext2 doesn't reliably provide block
> > allocations that are aligned to 2MiB. In my testing I've been unable to
> > get ext2 to actually fault in a PMD. It always fails with a "pfn
> > unaligned" message because the sector returned by ext2_get_block() isn't
> > aligned.
> >
> > I've tried various settings for the "stride" and "stripe_width" extended
> > options to mkfs.ext2, without any luck.
> >
> > Since we can't reliably get PMDs, remove support so that we don't have an
> > untested code path that we may someday traverse when we happen to get an
> > aligned block allocation. This should also make 4k DAX faults in ext2 a
> > bit faster since they will no longer have to call the PMD fault handler
> > only to get a response of VM_FAULT_FALLBACK.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ....
> > @@ -154,7 +133,6 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
> >
> > static const struct vm_operations_struct ext2_dax_vm_ops = {
> > .fault = ext2_dax_fault,
> > - .pmd_fault = ext2_dax_pmd_fault,
> > .page_mkwrite = ext2_dax_fault,
> > .pfn_mkwrite = ext2_dax_pfn_mkwrite,
> > };
>
> Would it be better to put a comment mentioning this here? So as the
> years go by, this reminds people not to bother trying to implement
> it?
>
> /*
> * .pmd_fault is not supported for DAX because allocation in ext2
> * cannot be reliably aligned to huge page sizes and so pmd faults
> * will always fail and fail back to regular faults.
> */
Sure, this seems like a good idea. I'll add it, thanks.
next prev parent reply other threads:[~2016-09-28 18:46 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 20:47 [PATCH v3 00/11] re-enable DAX PMD support Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 01/11] ext4: allow DAX writeback for hole punch Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 02/11] ext4: tell DAX the size of allocation holes Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 03/11] dax: remove buffer_size_valid() Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 04/11] ext2: remove support for DAX PMD faults Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 21:47 ` Dave Chinner
2016-09-27 21:47 ` Dave Chinner
2016-09-27 21:47 ` Dave Chinner
2016-09-27 21:47 ` Dave Chinner
2016-09-27 21:47 ` Dave Chinner
2016-09-28 18:46 ` Ross Zwisler [this message]
2016-09-28 18:46 ` Ross Zwisler
2016-09-28 18:46 ` Ross Zwisler
2016-09-28 18:46 ` Ross Zwisler
2016-09-28 18:46 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 05/11] dax: make 'wait_table' global variable static Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 06/11] dax: consistent variable naming for DAX entries Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 07/11] dax: coordinate locking for offsets in PMD range Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` [PATCH v3 08/11] dax: remove dax_pmd_fault() Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:47 ` Ross Zwisler
2016-09-27 20:48 ` [PATCH v3 09/11] dax: add struct iomap based DAX PMD support Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 22:14 ` Dave Chinner
2016-09-27 22:14 ` Dave Chinner
2016-09-27 22:14 ` Dave Chinner
2016-09-27 22:14 ` Dave Chinner
2016-09-29 18:20 ` Ross Zwisler
2016-09-29 18:20 ` Ross Zwisler
2016-09-29 18:20 ` Ross Zwisler
2016-09-29 18:20 ` Ross Zwisler
2016-09-29 18:20 ` Ross Zwisler
2016-09-27 20:48 ` [PATCH v3 10/11] xfs: use struct iomap based DAX PMD fault path Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` [PATCH v3 11/11] dax: remove "depends on BROKEN" from FS_DAX_PMD Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-27 20:48 ` Ross Zwisler
2016-09-28 2:08 ` [PATCH v3 00/11] re-enable DAX PMD support Christoph Hellwig
2016-09-28 2:08 ` Christoph Hellwig
2016-09-28 4:55 ` Dave Chinner
2016-09-28 4:55 ` Dave Chinner
2016-09-29 18:23 ` Ross Zwisler
2016-09-29 18:23 ` Ross Zwisler
2016-09-29 18:23 ` Ross Zwisler
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