linux-kernel - Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw

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Date:	Tue, 14 Jul 2015 00:42:37 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Dave Chinner <david@...morbit.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Daniel Wagner <daniel.wagner@...-carit.de>,
	Davidlohr Bueso <dave@...olabs.net>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw_semaphore

On 07/14, Dave Chinner wrote:
>
> [ Please cc linux-fsdevel@...r.kernel.org on filesystem
> infrastructure changes! ]

OK, will do.

> On Mon, Jul 13, 2015 at 11:25:36PM +0200, Oleg Nesterov wrote:
> >
> > 	- sb_lockdep_release() and sb_lockdep_acquire() play with
> > 	  percpu_rw_semaphore's internals.
> >
> > 	  Trivial, we need a couple of new helper in percpu-rwsem.c.
>
> 	- try compiling XFS, watch it break on freeze lockdep
> 	  annotations

Thanks a lot! I see. Still trivial, xfs can use the same helpers
rather the abuse lockdep directly.

> > 	- Most probably I missed something else, and I do not need
> > 	  how to test.
>
> xfstests has many freeze related stress tests.  IIRC, generic/068 is
> the test that historically causes the most problems for freeze
> infrastructure changes. You'll also need to test at least ext4, XFS
> and btrfs, because they all stress the freeze code differently.
> Testing XFS, in particular, is a good idea because it has several
> custom freeze tests that aren't run on any other filesystem type.

Thanks again.

Do you see something fundamentally wrong with this change?

Oleg.

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