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

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Date:   Mon, 4 Dec 2017 21:30:23 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Byungchul Park <byungchul.park@....com>
Cc:     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, mhocko@...e.com,
        pombredanne@...b.com, vinmenon@...eaurora.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 0/4] lockdep/crossrelease: Apply crossrelease to page
 locks

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.

I also don't like it that you've made CONFIG_LOCKDEP_PAGELOCK not
individually selectable.  I might well want a kernel with crosslock
support, but only for completions.