From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-nvdimm@lists.01.org, NeilBrown <neilb@suse.com>, Wilcox,
Subject: Re: [RFC v2] [PATCH 0/10] DAX page fault locking
Date: Tue, 22 Mar 2016 13:32:12 -0600 [thread overview]
Message-ID: <20160322193212.GA11164@linux.intel.com> (raw)
In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz>
On Mon, Mar 21, 2016 at 02:22:45PM +0100, Jan Kara wrote:
> [Sorry for repost but I accidentally sent initial email without patches]
>
> Hello,
>
> this is my second attempt at DAX page fault locking rewrite. Things now
> work reasonably well, it has survived full xfstests run on ext4. I guess
> I need to do more mmap targetted tests to unveil issues. Guys what do you
> used for DAX testing?
I typically use xfstests for regression testing. If we can come up with new
generally useful regression tests, especially ones concerning mmap races, that
would be awesome. I guess it's just a choice between adding them somewhere in
xfstests or somewhere else like with the unit tests in ndctl.
> Changes since v1:
> - handle wakeups of exclusive waiters properly
> - fix cow fault races
> - other minor stuff
>
> General description
>
> The basic idea is that we use a bit in an exceptional radix tree entry as
> a lock bit and use it similarly to how page lock is used for normal faults.
> That way we fix races between hole instantiation and read faults of the
> same index. For now I have disabled PMD faults since there the issues with
> page fault locking are even worse. Now that Matthew's multi-order radix tree
> has landed, I can have a look into using that for proper locking of PMD faults
> but first I want normal pages sorted out.
>
> In the end I have decided to implement the bit locking directly in the DAX
> code. Originally I was thinking we could provide something generic directly
> in the radix tree code but the functions DAX needs are rather specific.
> Maybe someone else will have a good idea how to distill some generally useful
> functions out of what I've implemented for DAX but for now I didn't bother
> with that.
>
> Honza
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WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org, "Wilcox,
Matthew R" <matthew.r.wilcox@intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
linux-nvdimm@lists.01.org, NeilBrown <neilb@suse.com>,
Jeff Moyer <jmoyer@redhat.com>
Subject: Re: [RFC v2] [PATCH 0/10] DAX page fault locking
Date: Tue, 22 Mar 2016 13:32:12 -0600 [thread overview]
Message-ID: <20160322193212.GA11164@linux.intel.com> (raw)
In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz>
On Mon, Mar 21, 2016 at 02:22:45PM +0100, Jan Kara wrote:
> [Sorry for repost but I accidentally sent initial email without patches]
>
> Hello,
>
> this is my second attempt at DAX page fault locking rewrite. Things now
> work reasonably well, it has survived full xfstests run on ext4. I guess
> I need to do more mmap targetted tests to unveil issues. Guys what do you
> used for DAX testing?
I typically use xfstests for regression testing. If we can come up with new
generally useful regression tests, especially ones concerning mmap races, that
would be awesome. I guess it's just a choice between adding them somewhere in
xfstests or somewhere else like with the unit tests in ndctl.
> Changes since v1:
> - handle wakeups of exclusive waiters properly
> - fix cow fault races
> - other minor stuff
>
> General description
>
> The basic idea is that we use a bit in an exceptional radix tree entry as
> a lock bit and use it similarly to how page lock is used for normal faults.
> That way we fix races between hole instantiation and read faults of the
> same index. For now I have disabled PMD faults since there the issues with
> page fault locking are even worse. Now that Matthew's multi-order radix tree
> has landed, I can have a look into using that for proper locking of PMD faults
> but first I want normal pages sorted out.
>
> In the end I have decided to implement the bit locking directly in the DAX
> code. Originally I was thinking we could provide something generic directly
> in the radix tree code but the functions DAX needs are rather specific.
> Maybe someone else will have a good idea how to distill some generally useful
> functions out of what I've implemented for DAX but for now I didn't bother
> with that.
>
> Honza
next prev parent reply other threads:[~2016-03-22 19:33 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-21 13:22 [RFC v2] [PATCH 0/10] DAX page fault locking Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-21 13:22 ` [PATCH 01/10] DAX: move RADIX_DAX_ definitions to dax.c Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-21 17:25 ` Matthew Wilcox
2016-03-21 17:25 ` Matthew Wilcox
2016-03-21 13:22 ` [PATCH 02/10] radix-tree: make 'indirect' bit available to exception entries Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-21 17:34 ` Matthew Wilcox
2016-03-21 17:34 ` Matthew Wilcox
2016-03-22 9:12 ` Jan Kara
2016-03-22 9:12 ` Jan Kara
2016-03-22 9:27 ` Matthew Wilcox
2016-03-22 9:27 ` Matthew Wilcox
2016-03-22 10:37 ` Jan Kara
2016-03-22 10:37 ` Jan Kara
2016-03-23 16:41 ` Ross Zwisler
2016-03-23 16:41 ` Ross Zwisler
2016-03-24 12:31 ` Jan Kara
2016-03-24 12:31 ` Jan Kara
2016-03-21 13:22 ` [PATCH 03/10] dax: Remove complete_unwritten argument Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-23 17:12 ` Ross Zwisler
2016-03-23 17:12 ` Ross Zwisler
2016-03-24 12:32 ` Jan Kara
2016-03-24 12:32 ` Jan Kara
2016-03-21 13:22 ` [PATCH 04/10] dax: Fix data corruption for written and mmapped files Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-23 17:39 ` Ross Zwisler
2016-03-23 17:39 ` Ross Zwisler
2016-03-24 12:51 ` Jan Kara
2016-03-24 12:51 ` Jan Kara
2016-03-29 15:17 ` Ross Zwisler
2016-03-29 15:17 ` Ross Zwisler
2016-03-21 13:22 ` [PATCH 05/10] dax: Allow DAX code to replace exceptional entries Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-23 17:52 ` Ross Zwisler
2016-03-23 17:52 ` Ross Zwisler
2016-03-24 10:42 ` Jan Kara
2016-03-24 10:42 ` Jan Kara
2016-03-21 13:22 ` [PATCH 06/10] dax: Remove redundant inode size checks Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-23 21:08 ` Ross Zwisler
2016-03-23 21:08 ` Ross Zwisler
2016-03-21 13:22 ` [PATCH 07/10] dax: Disable huge page handling Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-23 20:50 ` Ross Zwisler
2016-03-23 20:50 ` Ross Zwisler
2016-03-24 12:56 ` Jan Kara
2016-03-24 12:56 ` Jan Kara
2016-03-21 13:22 ` [PATCH 08/10] dax: New fault locking Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-29 21:57 ` Ross Zwisler
2016-03-29 21:57 ` Ross Zwisler
2016-03-31 16:27 ` Jan Kara
2016-03-31 16:27 ` Jan Kara
2016-03-21 13:22 ` [PATCH 09/10] dax: Use radix tree entry lock to protect cow faults Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-21 19:11 ` Matthew Wilcox
2016-03-21 19:11 ` Matthew Wilcox
2016-03-22 7:03 ` Jan Kara
2016-03-22 7:03 ` Jan Kara
2016-03-29 22:18 ` Ross Zwisler
2016-03-29 22:18 ` Ross Zwisler
2016-03-21 13:22 ` [PATCH 10/10] dax: Remove i_mmap_lock protection Jan Kara
2016-03-21 13:22 ` Jan Kara
2016-03-29 22:17 ` Ross Zwisler
2016-03-29 22:17 ` Ross Zwisler
2016-03-21 17:41 ` [RFC v2] [PATCH 0/10] DAX page fault locking Matthew Wilcox
2016-03-21 17:41 ` Matthew Wilcox
2016-03-23 15:09 ` Jan Kara
2016-03-23 15:09 ` Jan Kara
2016-03-23 20:50 ` Matthew Wilcox
2016-03-23 20:50 ` Matthew Wilcox
2016-03-24 10:00 ` Matthew Wilcox
2016-03-24 10:00 ` Matthew Wilcox
2016-03-22 19:32 ` Ross Zwisler [this message]
2016-03-22 19:32 ` Ross Zwisler
2016-03-22 21:07 ` Toshi Kani
2016-03-22 21:07 ` Toshi Kani
2016-03-22 21:15 ` Dave Chinner
2016-03-22 21:15 ` Dave Chinner
2016-03-23 9:45 ` Jan Kara
2016-03-23 9:45 ` Jan Kara
2016-03-23 15:11 ` Toshi Kani
2016-03-23 15:11 ` Toshi Kani
-- strict thread matches above, loose matches on Subject: below --
2016-03-21 13:21 Jan Kara
2016-03-21 13:21 ` Jan Kara
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