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Date:   Mon, 16 May 2022 15:55:54 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc:     Evgeniy Dushistov <dushistov@mail.ru>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Ira Weiny <ira.weiny@intel.com>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] fs/ufs: Replace kmap() with kmap_local_page()
Message-ID: <YoJl+lh0QELbv/TL@casper.infradead.org>
References: <20220516101925.15272-1-fmdefrancesco@gmail.com>
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On Mon, May 16, 2022 at 12:19:25PM +0200, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page(). With
> kmap_local_page(), the mapping is per thread, CPU local and not globally
> visible.
> 
> The usage of kmap_local_page() in fs/ufs is pre-thread, therefore replace
> kmap() / kunmap() calls with kmap_local_page() / kunmap_local().
> 
> kunmap_local() requires the mapping address, so return that address from
> ufs_get_page() to be used in ufs_put_page().
> 
> These changes are essentially ported from fs/ext2 and are largely based on
> commit 782b76d7abdf ("fs/ext2: Replace kmap() with kmap_local_page()").
> 
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Have you done more than compile-tested this?  I'd like to know that it's
been tested on a machine with HIGHMEM enabled (in a VM, presumably).
UFS doesn't get a lot of testing, and it'd be annoying to put out a
patch that breaks the kmap_local() rules.