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From: Boaz Harrosh <boaz@plexistor.com>
To: Dave Chinner <david@fromorbit.com>,
	Matthew Wilcox <matthew.r.wilcox@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Jan Kara <jack@suse.cz>, Hugh Dickins <hughd@google.com>,
	Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-nvdimm <linux-nvdimm@ml01.01.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Eryu Guan <eguan@redhat.com>,
	Christoph Hellwig <hch@infradead.org>
Cc: Stable Tree <stable@vger.kernel.org>
Subject: [PATCH 0/3 v5] dax: some dax fixes and cleanups
Date: Tue, 07 Apr 2015 11:33:09 +0300	[thread overview]
Message-ID: <55239645.9000507@plexistor.com> (raw)

Hi Andrew

I finally had the time to beat up these fixes based on linux-next/akpm
and it looks OK.
I'm sending the two fix patches with @stable + a patch-1 for the 4.0
Kernel. The 4.1-rc Kernel will need a different patch.

It is your call if you want these in stable. It is a breakage in the dax
code that went into 4.0. But I guess it will not have that many users right
at the get go. So feel free to remove the CC:@stable. (Also the old XIP that
this DAX changed had all the same problems)

[v5]
* A new patch-1 Based on linux-next/akpm branch because mm/memory.c
  completely changed there.
  Also a 4.0 version of the same patch-1 if needed for stable@

List of patches:
 [PATCH 1/3] mm(v4.1): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP
 [PATCH 2/3] dax: use pfn_mkwrite to update c/mtime + freeze
 [PATCH 3/3] dax: Unify ext2/4_{dax,}_file_operations

	All these patches are based on linux-next/akpm. I'm not sure how
	it will interact with ext4-next though.

 [PATCH 1/3 @stable] mm(v4.0): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP

	This patch is for 4.0 based tree if we decide to send
	[PATCH 2/3] to stable.


[v4] dax: some dax fixes and cleanups
* First patch fixed according to Andrew's comments. Thanks Andrew.
  1st and 2nd patch can go into current Kernel as they fix something
  that was merged this release.
* Added a new patch to fix up splice in the dax case, and cleanup.
  This one can wait for 4.1 (Also the first two not that anyone uses dax
  in production.)
* DAX freeze is not fixed yet. As we have more problems then I originally
  hoped for, as pointed out by Dave.
  (Just as a referance I'm sending a NO-GOOD additional patch to show what
   is not good enough to do. Was the RFC of [v3])
* Not re-posting the xfstest Dave please pick this up (It already found bugs
  in none dax FSs)

[v3] dax: Fix mmap-write not updating c/mtime
* I'm re-posting the two DAX patches that fix the mmap-write after read
  problem with DAX. (No changes since [v2])
* I'm also posting a 3rd RFC patch to address what Jan said about fs_freeze
  and making mapping read-only. 
  Jan Please review and see if this is what you meant.

[v2]
Jan Kara has pointed out that if we add the
sb_start/end_pagefault pair in the new pfn_mkwrite we
are then fixing another bug where: A user could start
writing to the page while filesystem is frozen.

[v1]
The main problem is that current mm/memory.c will no call us with page_mkwrite
if we do not have an actual page mapping, which is what DAX uses.
The solution presented here introduces a new pfn_mkwrite to solve this problem.
Please see patch-2 for details.

I've been running with this patch for 4 month both HW and VMs with no apparent
danger, but see patch-1 I played it safe.

I am also posting an xfstest 080 that demonstrate this problem, I believe
that also some git operations (can't remember which) suffer from this problem.
Actually Eryu Guan found that this test fails on some other FS as well.

Matthew hi
I would love to have your ACK on these patches?

Thanks
Boaz

WARNING: multiple messages have this Message-ID
From: Boaz Harrosh <boaz@plexistor.com>
To: Dave Chinner <david@fromorbit.com>,
	Matthew Wilcox <matthew.r.wilcox@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Jan Kara <jack@suse.cz>, Hugh Dickins <hughd@google.com>,
	Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-nvdimm <linux-nvdimm@ml01.01.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Eryu Guan <eguan@redhat.com>,
	Christoph Hellwig <hch@infradead.org>
Cc: Stable Tree <stable@vger.kernel.org>
Subject: [PATCH 0/3 v5] dax: some dax fixes and cleanups
Date: Tue, 07 Apr 2015 11:33:09 +0300	[thread overview]
Message-ID: <55239645.9000507@plexistor.com> (raw)

Hi Andrew

I finally had the time to beat up these fixes based on linux-next/akpm
and it looks OK.
I'm sending the two fix patches with @stable + a patch-1 for the 4.0
Kernel. The 4.1-rc Kernel will need a different patch.

It is your call if you want these in stable. It is a breakage in the dax
code that went into 4.0. But I guess it will not have that many users right
at the get go. So feel free to remove the CC:@stable. (Also the old XIP that
this DAX changed had all the same problems)

[v5]
* A new patch-1 Based on linux-next/akpm branch because mm/memory.c
  completely changed there.
  Also a 4.0 version of the same patch-1 if needed for stable@

List of patches:
 [PATCH 1/3] mm(v4.1): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP
 [PATCH 2/3] dax: use pfn_mkwrite to update c/mtime + freeze
 [PATCH 3/3] dax: Unify ext2/4_{dax,}_file_operations

	All these patches are based on linux-next/akpm. I'm not sure how
	it will interact with ext4-next though.

 [PATCH 1/3 @stable] mm(v4.0): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP

	This patch is for 4.0 based tree if we decide to send
	[PATCH 2/3] to stable.


[v4] dax: some dax fixes and cleanups
* First patch fixed according to Andrew's comments. Thanks Andrew.
  1st and 2nd patch can go into current Kernel as they fix something
  that was merged this release.
* Added a new patch to fix up splice in the dax case, and cleanup.
  This one can wait for 4.1 (Also the first two not that anyone uses dax
  in production.)
* DAX freeze is not fixed yet. As we have more problems then I originally
  hoped for, as pointed out by Dave.
  (Just as a referance I'm sending a NO-GOOD additional patch to show what
   is not good enough to do. Was the RFC of [v3])
* Not re-posting the xfstest Dave please pick this up (It already found bugs
  in none dax FSs)

[v3] dax: Fix mmap-write not updating c/mtime
* I'm re-posting the two DAX patches that fix the mmap-write after read
  problem with DAX. (No changes since [v2])
* I'm also posting a 3rd RFC patch to address what Jan said about fs_freeze
  and making mapping read-only. 
  Jan Please review and see if this is what you meant.

[v2]
Jan Kara has pointed out that if we add the
sb_start/end_pagefault pair in the new pfn_mkwrite we
are then fixing another bug where: A user could start
writing to the page while filesystem is frozen.

[v1]
The main problem is that current mm/memory.c will no call us with page_mkwrite
if we do not have an actual page mapping, which is what DAX uses.
The solution presented here introduces a new pfn_mkwrite to solve this problem.
Please see patch-2 for details.

I've been running with this patch for 4 month both HW and VMs with no apparent
danger, but see patch-1 I played it safe.

I am also posting an xfstest 080 that demonstrate this problem, I believe
that also some git operations (can't remember which) suffer from this problem.
Actually Eryu Guan found that this test fails on some other FS as well.

Matthew hi
I would love to have your ACK on these patches?

Thanks
Boaz

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             reply	other threads:[~2015-04-07  8:33 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-07  8:33 Boaz Harrosh [this message]
2015-04-07  8:33 ` [PATCH 0/3 v5] dax: some dax fixes and cleanups Boaz Harrosh
2015-04-07  8:40 ` [PATCH 1/3] mm(v4.1): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP Boaz Harrosh
2015-04-07  8:51   ` Boaz Harrosh
2015-04-07  8:51     ` Boaz Harrosh
2015-04-07  9:03   ` Kirill A. Shutemov
2015-04-07  9:22     ` Boaz Harrosh
2015-04-07 12:57   ` [PATCH 1/3 v6] " Boaz Harrosh
2015-04-07 12:57     ` Boaz Harrosh
2015-04-07 13:17     ` Kirill A. Shutemov
2015-04-07 13:26       ` Kirill A. Shutemov
2015-04-07 13:37         ` Boaz Harrosh
2015-04-07 13:37           ` Boaz Harrosh
2015-04-07 13:47           ` Kirill A. Shutemov
2015-04-07 14:09             ` Boaz Harrosh
2015-04-07 14:09               ` Boaz Harrosh
2015-04-07 14:06   ` [PATCH 1/3 v7] " Boaz Harrosh
2015-04-07 14:06     ` Boaz Harrosh
2015-04-07 14:12     ` Kirill A. Shutemov
2015-04-07  8:43 ` [PATCH 2/3] dax: use pfn_mkwrite to update c/mtime + freeze protection Boaz Harrosh
2015-04-07  8:43   ` Boaz Harrosh
2015-04-07 16:28   ` Jan Kara
2015-04-07 16:28     ` Jan Kara
2015-04-07  8:45 ` [PATCH 3/3] dax: Unify ext2/4_{dax,}_file_operations Boaz Harrosh
2015-04-07  8:45   ` Boaz Harrosh
2015-04-07 16:26   ` Jan Kara
2015-04-08 15:56 ` [PATCH 1/3 @stable] mm(v4.0): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP Boaz Harrosh
2015-04-08 15:56   ` Boaz Harrosh
2015-04-08 16:00   ` Boaz Harrosh
2015-04-08 16:00     ` Boaz Harrosh
2015-04-08 20:26     ` Greg KH
2015-04-12  7:49       ` Boaz Harrosh
2015-04-12  7:49         ` Boaz Harrosh

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