linux-kernel - Re: [PATCH 01/10] mm: page_ref_add_unless() does not trace 'u' argument

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Message-ID: <YbEbvwU81QKK/wUu@casper.infradead.org>
Date:   Wed, 8 Dec 2021 20:55:27 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-m68k@...ts.linux-m68k.org, anshuman.khandual@....com,
        akpm@...ux-foundation.org, william.kucharski@...cle.com,
        mike.kravetz@...cle.com, vbabka@...e.cz, geert@...ux-m68k.org,
        schmitzmic@...il.com, rostedt@...dmis.org, mingo@...hat.com,
        hannes@...xchg.org, guro@...com, songmuchun@...edance.com,
        weixugc@...gle.com, gthelen@...gle.com, rientjes@...gle.com,
        pjt@...gle.com
Subject: Re: [PATCH 01/10] mm: page_ref_add_unless() does not trace 'u'
 argument

On Wed, Dec 08, 2021 at 08:35:35PM +0000, Pasha Tatashin wrote:
> In other page_ref_* functions all arguments and returns are traced, but
> in page_ref_add_unless the 'u' argument which stands for unless boolean
> is not traced. However, what is more confusing is that in the tracing
> routine:
> 	__page_ref_mod_unless(struct page *page, int v, int u);
> 
> The 'u' argument present, but instead a return value is passed into
> this argument.
> 
> Add a new template specific for page_ref_add_unless(), and trace all
> arguments and the return value.

The special casing of '1' for device pages is going away, so NAK
to this user-visible change.