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From: Jan Kara <jack@suse.cz>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org
Subject: Re: [PATCH 14/15] dax: Protect PTE modification on WP fault by radix tree entry lock
Date: Tue, 26 Jul 2016 16:09:30 +0200	[thread overview]
Message-ID: <20160726140930.GD6860@quack2.suse.cz> (raw)
In-Reply-To: <20160725213059.GA19713@linux.intel.com>

On Mon 25-07-16 15:30:59, Ross Zwisler wrote:
> On Fri, Jul 22, 2016 at 02:19:40PM +0200, Jan Kara wrote:
> > Currently PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite()
> > has released corresponding radix tree entry lock. When we want to
> > writeprotect PTE on cache flush, we need PTE modification to happen
> > under radix tree entry lock to ensure consisten updates of PTE and radix
> > tree (standard faults use page lock to ensure this consistency). So move
> > update of PTE bit into dax_pfn_mkwrite().
> > 
> > Signed-off-by: Jan Kara <jack@suse.cz>
> 
> After applying the whole series to a v4.7 baseline I was hitting a deadlock in
> my testing, and it bisected to this commit.  This deadlock happens in my QEMU
> guest with generic/068, ext4 and DAX.  It reproduces 100% of the time after
> this commit.
> 
> Here is the lockdep info, passed through kasan_symbolize.py:

Thanks! I've checked why I didn't see this and apparently I've run last
round of testing on the wrong branch. Drat.

I've fixed the bug you've spotted (we need to release tree_lock earlier)
but xfstests are triggering some more issues now for me so I'm debugging
those.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR
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Linux-nvdimm@lists.01.org
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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-nvdimm@lists.01.org,
	Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 14/15] dax: Protect PTE modification on WP fault by radix tree entry lock
Date: Tue, 26 Jul 2016 16:09:30 +0200	[thread overview]
Message-ID: <20160726140930.GD6860@quack2.suse.cz> (raw)
In-Reply-To: <20160725213059.GA19713@linux.intel.com>

On Mon 25-07-16 15:30:59, Ross Zwisler wrote:
> On Fri, Jul 22, 2016 at 02:19:40PM +0200, Jan Kara wrote:
> > Currently PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite()
> > has released corresponding radix tree entry lock. When we want to
> > writeprotect PTE on cache flush, we need PTE modification to happen
> > under radix tree entry lock to ensure consisten updates of PTE and radix
> > tree (standard faults use page lock to ensure this consistency). So move
> > update of PTE bit into dax_pfn_mkwrite().
> > 
> > Signed-off-by: Jan Kara <jack@suse.cz>
> 
> After applying the whole series to a v4.7 baseline I was hitting a deadlock in
> my testing, and it bisected to this commit.  This deadlock happens in my QEMU
> guest with generic/068, ext4 and DAX.  It reproduces 100% of the time after
> this commit.
> 
> Here is the lockdep info, passed through kasan_symbolize.py:

Thanks! I've checked why I didn't see this and apparently I've run last
round of testing on the wrong branch. Drat.

I've fixed the bug you've spotted (we need to release tree_lock earlier)
but xfstests are triggering some more issues now for me so I'm debugging
those.

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

--
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  reply	other threads:[~2016-07-26 14:09 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-22 12:19 [PATCH 0/15 v2] dax: Clear dirty bits after flushing caches Jan Kara
2016-07-22 12:19 ` Jan Kara
2016-07-22 12:19 ` [PATCH 01/15] mm: Create vm_fault structure earlier Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 02/15] mm: Propagate original vm_fault into do_fault_around() Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 03/15] mm: Add pmd and orig_pte fields to vm_fault Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 04/15] mm: Allow full handling of COW faults in ->fault handlers Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 05/15] mm: Factor out functionality to finish page faults Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 06/15] mm: Move handling of COW faults into DAX code Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 07/15] dax: Make cache flushing protected by entry lock Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 08/15] mm: Export follow_pte() Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 09/15] mm: Remove unnecessary vma->vm_ops check Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 10/15] mm: Factor out common parts of write fault handling Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 11/15] mm: Move part of wp_page_reuse() into the single call site Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 12/15] mm: Lift vm_fault structure creation from do_page_mkwrite() Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19 ` [PATCH 13/15] mm: Provide helper for finishing mkwrite faults Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-08-09 14:50   ` [lkp] [mm] 0c649028cd: vm-scalability.throughput 343.9% improvement kernel test robot
2016-08-09 14:50     ` kernel test robot
2016-08-09 14:50     ` kernel test robot
2016-08-09 14:50     ` kernel test robot
2016-07-22 12:19 ` [PATCH 14/15] dax: Protect PTE modification on WP fault by radix tree entry lock Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-25 21:30   ` Ross Zwisler
2016-07-25 21:30     ` Ross Zwisler
2016-07-26 14:09     ` Jan Kara [this message]
2016-07-26 14:09       ` Jan Kara
2016-07-22 12:19 ` [PATCH 15/15] dax: Clear dirty entry tags on cache flush Jan Kara
2016-07-22 12:19   ` Jan Kara
2016-07-22 12:19   ` Jan Kara

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