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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 28 Apr 2021 09:50:01 -0700
Message-ID: <CAHk-=wimsMqGdzik187YWLb-ru+iktb4MYbMQG1rnZ81dXYFVg@mail.gmail.com>
Subject: Re: [GIT PULL] iomap: new code for 5.13-rc1
To:     Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc:     Christoph Hellwig <hch@lst.de>,
        "Darrick J. Wong" <djwong@kernel.org>, Jia He <justin.he@arm.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        Dave Chinner <david@fromorbit.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Eric Sandeen <sandeen@sandeen.net>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
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[ Added Andy, who replied to the separate thread where Jia already
posted the patch ]

On Wed, Apr 28, 2021 at 12:38 AM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> So the patch makes sense to me. If somebody says '%pD5', it would get
> capped at 4 instead of being forced down to 1. But note that while that
> grep only produces ~36 hits, it also affects %pd, of which there are
> ~200 without a 2-4 following (including some vsprintf test cases that
> would break). So I think one would first have to explicitly support '1',
> switch over some users by adding that 1 in their format string
> (test_vsprintf in particular), then flip the default for 'no digit
> following %p[dD]'.

Yeah, and the "show one name" actually makes sense for "%pd", because
that's about the *dentry*.

A dentry has a parent, yes, but at the same time, a dentry really does
inherently have "one name" (and given just the dentry pointers, you
can't show mount-related parenthood, so in many ways the "show just
one name" makes sense for "%pd" in ways it doesn't necessarily for
"%pD"). But while a dentry arguably has that "one primary component",
a _file_ is certainly not exclusively about that last component.

So you're right - my "how about something like this" patch is too
simplistic. The default number of components to show should be about
whether it's %pd or %pD.

That also does explain the arguably odd %pD defaults: %pd came first,
and then %pD came afterwards.

              Linus