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From: Jan Kara <jack@suse.cz>
To: linux-fsdevel@vger.kernel.org
Cc: Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org, NeilBrown <neilb@suse.com>,
	"Wilcox, Matthew R" <matthew.r.wilcox@intel.com>
Subject: [RFC] [PATCH 0/12] DAX page fault locking
Date: Thu, 10 Mar 2016 20:18:43 +0100	[thread overview]
Message-ID: <1457637535-21633-1-git-send-email-jack@suse.cz> (raw)

Hello,

this is my first attempt at DAX page fault locking rewrite. It is mostly
just a dump of current status of my git tree so that people can see where I'm
going before weekend. It should be complete but so far it is only compile
tested.

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. I think we will need something like
Matthew's multi-order radix tree to fix the races for PMD faults but I
want to have a look at those once locking for normal pages is working.

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: Jan Kara <jack@suse.cz>
To: linux-fsdevel@vger.kernel.org
Cc: "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>,
	Jan Kara <jack@suse.cz>
Subject: [RFC] [PATCH 0/12] DAX page fault locking
Date: Thu, 10 Mar 2016 20:18:43 +0100	[thread overview]
Message-ID: <1457637535-21633-1-git-send-email-jack@suse.cz> (raw)

Hello,

this is my first attempt at DAX page fault locking rewrite. It is mostly
just a dump of current status of my git tree so that people can see where I'm
going before weekend. It should be complete but so far it is only compile
tested.

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. I think we will need something like
Matthew's multi-order radix tree to fix the races for PMD faults but I
want to have a look at those once locking for normal pages is working.

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

             reply	other threads:[~2016-03-10 19:18 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-10 19:18 Jan Kara [this message]
2016-03-10 19:18 ` [RFC] [PATCH 0/12] DAX page fault locking Jan Kara
2016-03-10 19:18 ` [PATCH 01/12] DAX: move RADIX_DAX_ definitions to dax.c Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-11 22:54   ` Ross Zwisler
2016-03-11 22:54     ` Ross Zwisler
2016-03-10 19:18 ` [PATCH 02/12] radix-tree: make 'indirect' bit available to exception entries Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 03/12] mm: Remove VM_FAULT_MINOR Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:38   ` Wilcox, Matthew R
2016-03-10 19:38     ` Wilcox, Matthew R
2016-03-10 19:48     ` Jan Kara
2016-03-10 19:48       ` Jan Kara
2016-03-10 19:18 ` [PATCH 04/12] ocfs2: Fix return value from ocfs2_page_mkwrite() Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 05/12] dax: Remove synchronization using i_mmap_lock Jan Kara
2016-03-10 19:55   ` Wilcox, Matthew R
2016-03-10 19:55     ` Wilcox, Matthew R
2016-03-10 20:05     ` Jan Kara
2016-03-10 20:05       ` Jan Kara
2016-03-10 20:10       ` Wilcox, Matthew R
2016-03-10 20:10         ` Wilcox, Matthew R
2016-03-14 10:01         ` Jan Kara
2016-03-14 10:01           ` Jan Kara
2016-03-14 14:51           ` Wilcox, Matthew R
2016-03-14 14:51             ` Wilcox, Matthew R
2016-03-15  9:50             ` Jan Kara
2016-03-15  9:50               ` Jan Kara
2016-03-10 19:18 ` [PATCH 06/12] dax: Remove complete_unwritten argument Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 07/12] dax: Fix data corruption for written and mmapped files Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 08/12] dax: Fix bogus fault return value on cow faults Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 09/12] dax: Allow DAX code to replace exceptional entries Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 10/12] dax: Remove redundant inode size checks Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 19:18 ` [PATCH 11/12] dax: Disable huge page handling Jan Kara
2016-03-10 19:34   ` Dan Williams
2016-03-10 19:34     ` Dan Williams
2016-03-10 19:52     ` Jan Kara
2016-03-10 19:52       ` Jan Kara
2016-03-10 19:18 ` [PATCH 12/12] dax: New fault locking Jan Kara
2016-03-10 19:18   ` Jan Kara
2016-03-10 23:54   ` NeilBrown
2016-03-10 23:54     ` NeilBrown
2016-03-15 21:34     ` NeilBrown
2016-03-15 21:34       ` NeilBrown
2016-03-18 14:16       ` Jan Kara
2016-03-18 14:16         ` Jan Kara
2016-03-18 15:39         ` Jan Kara
2016-03-18 15:39           ` Jan Kara
2016-03-22 21:10           ` NeilBrown
2016-03-22 21:10             ` NeilBrown
2016-03-23 11:00             ` Jan Kara
2016-03-23 11:00               ` Jan Kara
2016-03-31  4:20               ` NeilBrown
2016-03-31  4:20                 ` NeilBrown
2016-03-31  8:54                 ` Jan Kara
2016-03-31  8:54                   ` Jan Kara
2016-04-01  0:34                   ` NeilBrown
2016-04-01  0:34                     ` NeilBrown

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