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From: Jan Kara <jack@suse.cz>
To: "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>
Cc: Jan Kara <jack@suse.cz>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	NeilBrown <neilb@suse.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 05/12] dax: Remove synchronization using i_mmap_lock
Date: Tue, 15 Mar 2016 10:50:56 +0100	[thread overview]
Message-ID: <20160315095056.GE17942@quack.suse.cz> (raw)
In-Reply-To: <100D68C7BA14664A8938383216E40DE0422086AA@FMSMSX114.amr.corp.intel.com>

On Mon 14-03-16 14:51:26, Wilcox, Matthew R wrote:
> I think the ultimate goal here has to be to have the truncate code lock
> the DAX entry in the radix tree and delete it.  Then we can have
> do_cow_fault() unlock the radix tree entry instead of the i_mmap_lock.
> So we'll need another element in struct vm_fault where we can pass back a
> pointer into the radix tree instead of a pointer to struct page (or add
> another bit to VM_FAULT_ that indicates that 'page' is not actually a
> page, but a pointer to an exceptional entry ... or have the MM code
> understand the exceptional bit ... there's a few ways we can go here).

Yes, with my last patch truncate already waits for lock in radix tree. And
I was looking into various ways how to cleanly handle cow faults using
the radix tree lock instead of i_mmap_lock. So far it's a bit hacky to my
taste but I agree we want to fix the race that way.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR
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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>
Cc: Jan Kara <jack@suse.cz>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Ross Zwisler <ross.zwisler@linux.intel.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	NeilBrown <neilb@suse.com>
Subject: Re: [PATCH 05/12] dax: Remove synchronization using i_mmap_lock
Date: Tue, 15 Mar 2016 10:50:56 +0100	[thread overview]
Message-ID: <20160315095056.GE17942@quack.suse.cz> (raw)
In-Reply-To: <100D68C7BA14664A8938383216E40DE0422086AA@FMSMSX114.amr.corp.intel.com>

On Mon 14-03-16 14:51:26, Wilcox, Matthew R wrote:
> I think the ultimate goal here has to be to have the truncate code lock
> the DAX entry in the radix tree and delete it.  Then we can have
> do_cow_fault() unlock the radix tree entry instead of the i_mmap_lock.
> So we'll need another element in struct vm_fault where we can pass back a
> pointer into the radix tree instead of a pointer to struct page (or add
> another bit to VM_FAULT_ that indicates that 'page' is not actually a
> page, but a pointer to an exceptional entry ... or have the MM code
> understand the exceptional bit ... there's a few ways we can go here).

Yes, with my last patch truncate already waits for lock in radix tree. And
I was looking into various ways how to cleanly handle cow faults using
the radix tree lock instead of i_mmap_lock. So far it's a bit hacky to my
taste but I agree we want to fix the race that way.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2016-03-15  9:50 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-10 19:18 [RFC] [PATCH 0/12] DAX page fault locking Jan Kara
2016-03-10 19:18 ` 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 [this message]
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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