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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 8 May 2021 15:47:38 -0700
Message-ID: <CAHk-=wiOPkSm-01yZzamTvX2RPdJ0784+uWa0OMK-at+3XDd0g@mail.gmail.com>
Subject: Re: [PATCH RFC 1/3] fs: introduce helper d_path_fast()
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Jia He <justin.he@arm.com>, Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Jonathan Corbet <corbet@lwn.net>,
        Al Viro <viro@ftp.linux.org.uk>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Eric Biggers <ebiggers@google.com>,
        "Ahmed S. Darwish" <a.darwish@linutronix.de>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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On Sat, May 8, 2021 at 3:42 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> But your READ_ONCE() is definitely the right thing to do (whether we
> do your re-org or not, and whether we do this "prepend_buffer" thing
> or not).

Oh, and looking at it some more, I think it would probably be a good
thing to make __dentry_path() take a

       struct prepend_buffer *orig

argument, the same way prepend_path() does. Also, like prepend_path(),
the terminating NUL should probably be done by the caller.

Doing those two changes would simplify the hackery we now have in
"dentry_path()" due to the "//deleted" games. The whole "restore '/'
that was overwritten by the NUL added by __dentry_path() is
unbelievably ugly.

            Linus