linux-kernel - Re: [PATCH v2 0/4] lockdep/crossrelease: Apply crossrelease to page locks

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Message-ID: <20171205085837.7oo6j5bp6y3xqope@dhcp22.suse.cz>
Date:   Tue, 5 Dec 2017 09:58:37 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Byungchul Park <byungchul.park@....com>, peterz@...radead.org,
        mingo@...nel.org, akpm@...ux-foundation.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-block@...r.kernel.org, kernel-team@....com, jack@...e.cz,
        jlayton@...hat.com, viro@...iv.linux.org.uk, hannes@...xchg.org,
        npiggin@...il.com, rgoldwyn@...e.com, vbabka@...e.cz,
        pombredanne@...b.com, vinmenon@...eaurora.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 0/4] lockdep/crossrelease: Apply crossrelease to page
 locks

On Mon 04-12-17 23:45:17, Matthew Wilcox wrote:
> On Tue, Dec 05, 2017 at 03:19:46PM +0900, Byungchul Park wrote:
> > On 12/5/2017 2:46 PM, Byungchul Park wrote:
> > > On 12/5/2017 2:30 PM, Matthew Wilcox wrote:
> > > > On Mon, Dec 04, 2017 at 02:16:19PM +0900, Byungchul Park wrote:
> > > > > For now, wait_for_completion() / complete() works with lockdep, add
> > > > > lock_page() / unlock_page() and its family to lockdep support.
> > > > > 
> > > > > Changes from v1
> > > > >   - Move lockdep_map_cross outside of page_ext to make it flexible
> > > > >   - Prevent allocating lockdep_map per page by default
> > > > >   - Add a boot parameter allowing the allocation for debugging
> > > > > 
> > > > > Byungchul Park (4):
> > > > >    lockdep: Apply crossrelease to PG_locked locks
> > > > >    lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked
> > > > >    lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext
> > > > >    lockdep: Add a boot parameter enabling to track page locks using
> > > > >      lockdep and disable it by default
> > > > 
> > > > I don't like the way you've structured this patch series; first adding
> > > > the lockdep map to struct page, then moving it to page_ext.
> > > 
> > > Hello,
> > > 
> > > I will make them into one patch.
> > 
> > I've thought it more.
> > 
> > Actually I did it because I thought I'd better make it into two
> > patches since it makes reviewers easier to review. It doesn't matter
> > which one I choose, but I prefer to split it.
> 
> I don't know whether it's better to make it all one patch or split it
> into multiple patches.  But it makes no sense to introduce it in struct
> page, then move it to struct page_ext.

I would tend to agree. It is not like anybody would like to apply only
the first part alone. Adding the necessary infrastructure to page_ext is
not such a big deal.

-- 
Michal Hocko
SUSE Labs