Hi

-----Original Message-----
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Sent: Wednesday, April 28, 2021 3:38 PM
To: Linus Torvalds <torvalds@linux-foundation.org>; Christoph Hellwig
[off-list ref]
Cc: Darrick J. Wong <djwong@kernel.org>; Justin He <redacted>; Al
Viro [off-list ref]; linux-fsdevel <linux-
fsdevel@vger.kernel.org>; linux-xfs [off-list ref]; Dave
Chinner [off-list ref]; Linux Kernel Mailing List <linux-
kernel@vger.kernel.org>; Eric Sandeen [off-list ref]
Subject: Re: [GIT PULL] iomap: new code for 5.13-rc1

On 28/04/2021 09.14, Linus Torvalds wrote:
So let me just quote that first reply of mine, because you seem to not

quoted

have seen it:

quoted

We have '%pD' for printing a filename. It may not be perfect (by
default it only prints one component, you can do "%pD4" to show up to
four components), but it should "JustWork(tm)".

And if it doesn't, we should fix it.

I really think %pD4 should be more than good enough. And I think maybe
we should make plain "%pD" mean "as much of the path that is
reasonable" rather than "as few components as possible" (ie 1).

So I don't think "%pD" (or "%pD4") is necessarily perfect, but I think
it's even worse when people then go and do odd ad-hoc things because
of some inconvenience in our %pD implementation.

For example, changing the default to be "show more by default" should
be as simple as something like the attached.  I do think that would be
the more natural behavior for %pD - don't limit it unnecessarily by
default, but for somebody who literally just wants to see a maximum of
2 components, using '%pD2' makes sense.

(Similarly, changing the limit of 4  components to something slightly
bigger would be trivial)

Hmm?

Grepping for existing users with

    git grep '%pD[^1-4]'

most of them would probably like a full pathname, and the odd s390
hmcdrv_dev.c use should just be fixed (it has a hardcoded "/dev/%pD",
which seems very wrong).

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]'.

I checked and found a few changes as follows, hoping I didn't miss else:
1. test_vsprintf %pD->%pD1  %pd->%pd1
2. drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c
../../../%pd3/%pd -> %pd
3. s390/hmcdrv as mentioned above

--
Cheers,
Justin (Jia He)

Rasmus

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