linux-kernel - Re: [PATCH v3 4/4] Documentation/vm: Rework "Temporary Virtual Mappings" section

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Message-ID: <YmrCKtGaCbD5SQtY@linutronix.de>
Date:   Thu, 28 Apr 2022 18:34:50 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Will Deacon <will@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, outreachy@...ts.linux.dev,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 4/4] Documentation/vm: Rework "Temporary Virtual
 Mappings" section

On 2022-04-28 13:14:30 [+0200], Fabio M. De Francesco wrote:
> > > +  should be only used if it is absolutely required, otherwise 
> kmap_local_page()
> > > +  should be used where it is feasible.
> > 
> > I'm not keen about the "absolutely required" wording and "feasible".
> > That said, the other pieces look good, thank you for the work.
> 
> I'll rewrite the last part of this sentence as it follows:
> 
> + should be only used if it is required, otherwise kmap_local_page()
> + should be preferred.

Yeah, my point is that it shouldn't be required. Using a kmap_atomic()
mapping only because it is not limited to a thread/ CPU sounds wrong.
This shouldn't be a valid requirement. Therefore kmap_local() should
always be the way to go.

Anyway, I can live with that and hopefully that interface will removed
soon :) You yourself, as you pointed out, removed a user or two so I'm
confident that it will happen at some point ;)

> Thank you so much for the time you have spent for reviewing and helping,

You are welcome.

> Fabio

Sebastian