linux-kernel - Re: [PATCH v5] mm, dax: fix DAX deadlocks

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Message-ID: <20151012225327.GF27164@dastard>
Date:	Tue, 13 Oct 2015 09:53:27 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Matthew Wilcox <willy@...ux.intel.com>,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Jan Kara <jack@...e.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-nvdimm@...ts.01.org,
	Matthew Wilcox <matthew.r.wilcox@...el.com>
Subject: Re: [PATCH v5] mm, dax: fix DAX deadlocks

On Wed, Oct 07, 2015 at 04:58:49PM -0600, Ross Zwisler wrote:
> The following two locking commits in the DAX code:
> 
> commit 843172978bb9 ("dax: fix race between simultaneous faults")
> commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX")
> 
> introduced a number of deadlocks and other issues which need to be fixed
> for the v4.3 kernel. The list of issues in DAX after these commits (some
> newly introduced by the commits, some preexisting) can be found here:
> 
> https://lkml.org/lkml/2015/9/25/602
> 
> This undoes most of the changes introduced by those two commits,
> essentially returning us to the DAX locking scheme that was used in v4.2.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>

I've run this through some testing, the deadlocks aren't present and
there don't appear to be any new regressions, so IMO this is fine to
go to Linus.

Tested-by: Dave Chinner <dchinner@...hat.com>

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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