linux-kernel - Re: [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local

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Date:   Fri, 8 Jul 2022 00:12:31 +0200
From:   David Sterba <dsterba@...e.cz>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     David Sterba <dsterba@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        Nick Terrell <terrelln@...com>, linux-btrfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "James E. J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        John David Anglin <dave.anglin@...l.net>,
        linux-parisc@...r.kernel.org
Subject: Re: [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in
 zstd.c

On Wed, Jul 06, 2022 at 01:15:18PM +0200, Fabio M. De Francesco wrote:
> This is a little series which serves the purpose to replace kmap() with
> kmap_local_page() in btrfs/zstd.c. Actually this task is only accomplished
> in patch 2/2.
> 
> Instead patch 1/2 is a pre-requisite for the above-mentioned replacement,
> however, above all else, it has the purpose to conform the prototypes of
> __kunmap_{local,atomic}() to their own correct semantics. Since those
> functions don't make changes to the memory pointed by their arguments,
> change the type of those arguments to become pointers to const void.
> 
> v5 -> v6: Delete an unnecessary assignment in 2/2 (thanks to Ira Weiny).
> 
> v4 -> v5: Use plain page_address() for pages which cannot come from Highmem
> (instead of kmapping them); remove unnecessary initializations to NULL
> in 2/2 (thanks to Ira Weiny).
> 
> v3 -> v4: Resend and add linux-mm to the list of recipients (thanks to
> Andrew Morton).
> 
> Fabio M. De Francesco (2):
>   highmem: Make __kunmap_{local,atomic}() take "const void *"
>   btrfs: Replace kmap() with kmap_local_page() in zstd.c

Added to the kmap patch queue, thanks. With all the other conversion
there are 5 patches

  highmem: Make __kunmap_{local,atomic}() take const void pointer
  btrfs: zstd: replace kmap() with kmap_local_page()
  btrfs: zlib: replace kmap() with kmap_local_page() in zlib_compress_pages()
  btrfs: zlib: replace kmap() with kmap_local_page() in zlib_decompress_bio()
  btrfs: replace kmap_atomic() with kmap_local_page()

and there are no kmap or kmap_atomic left in fs/btrfs, scheduled for 5.20.