linux-kernel - Re: [PATCH 2/2] exec: open code copy_string

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Message-ID: <20200501125049.GL23230@ZenIV.linux.org.uk>
Date:   Fri, 1 May 2020 13:50:49 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] exec: open code copy_string_kernel

On Fri, May 01, 2020 at 12:41:05PM +0200, Christoph Hellwig wrote:
> Currently copy_string_kernel is just a wrapper around copy_strings that
> simplifies the calling conventions and uses set_fs to allow passing a
> kernel pointer.  But due to the fact the we only need to handle a single
> kernel argument pointer, the logic can be sigificantly simplified while
> getting rid of the set_fs.

I can live with that...  BTW, why do we bother with flush_cache_page() (by
way of get_arg_page()) here and in copy_strings()?  How could *anything*
have accessed that page by its address in new mm - what are we trying to
flush here?