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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 7 Oct 2019 11:13:27 -0700
Message-ID: <CAHk-=wgSzPwzX0cHgTZ9SQrd8XWQcMnLkBCo_-710pLTEBFGYQ@mail.gmail.com>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
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On Mon, Oct 7, 2019 at 10:34 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Tangentially related: copy_regster_to_user() and copy_regset_from_user().

Not a worry. It's not performance-critical code, and if it ever is, it
needs to be rewritten anyway.


> The former variant tends to lead to few calls
> of __copy_{to,from}_user(); the latter...  On x86 it ends up doing
> this:

Just replace the __put_user() with a put_user() and be done with it.
That code isn't acceptable, and if somebody ever complains about
performance it's not the lack of __put_user that is the problem.

           Linus