linux-kernel - Re: [PATCH] fs: Replace kmap{,_atomic}() with kmap_local

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Message-ID: <5600017.DvuYhMxLoT@opensuse>
Date:   Sat, 09 Jul 2022 20:30:28 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Benjamin LaHaise <bcrl@...ck.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, nvdimm@...ts.linux.dev,
        io-uring@...r.kernel.org, linux-riscv@...ts.infradead.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] fs: Replace kmap{,_atomic}() with kmap_local_page()

On venerdì 8 luglio 2022 22:18:35 CEST Ira Weiny wrote:
> On Thu, Jun 30, 2022 at 06:35:27PM +0200, Fabio M. De Francesco wrote:
> > The use of kmap() and kmap_atomic() are being deprecated in favor of
> > kmap_local_page().
> > 
> > With kmap_local_page(), the mappings are per thread, CPU local and not
> > globally visible. Furthermore, the mappings can be acquired from any
> > context (including interrupts).
> > 
> > Therefore, use kmap_local_page() in exec.c because these mappings are 
per
> > thread, CPU local, and not globally visible.
> > 
> > Tested with xfstests on a QEMU + KVM 32-bits VM booting a kernel with
> > HIGHMEM64GB enabled.
> > 
> > Suggested-by: Ira Weiny <ira.weiny@...el.com>
> 
> This looks good but there is a kmap_atomic() in this file which I _think_ 
can
> be converted as well.  But that is good as a separate patch.
> 
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> 

Thanks for your review!

I didn't notice that kmap_atomic(). I'll send a conversion with a separate 
patch.

Fabio