linux-kernel - [PATCH RFC 0/3] make '%pD' print full path for file

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Message-Id: <20210508122530.1971-1-justin.he@arm.com>
Date:   Sat,  8 May 2021 20:25:27 +0800
From:   Jia He <justin.he@....com>
To:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@....linux.org.uk>
Cc:     Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Jia He <justin.he@....com>
Subject: [PATCH RFC 0/3] make '%pD' print full path for file

At [1], Linux suggested printing full path for file instead of printing
the components as '%pd'.

Typically, there is no need for printk specifiers to take any real locks
(ie mount_lock or rename_lock). So I introduce a new helper d_path_fast
which is similar to d_path except not taking any seqlock/spinlock.

The cases I tested:
1. print %pD with full path when opening a ext4 file
2. mount a ext4 filesystem upon a ext4 filesystem, and print the file
   with %pD
3. print the file full path which has more than 128 chars
4. all test_print selftests

After this set, I noticed there are many lines which contained "%pD[234]"
that should be changed to "%pD". I don't want to involve those
subsystems in this patch series before the helper is satisfied with
everyone.

You can get the lines by 
$find fs/ -name \*.[ch] | xargs grep -rn "\%pD[234]"
	 
[1] https://lore.kernel.org/lkml/CAHk-=wimsMqGdzik187YWLb-ru+iktb4MYbMQG1rnZ81dXYFVg@mail.gmail.com/

Jia He (3):
  fs: introduce helper d_path_fast()
  lib/vsprintf.c: make %pD print full path for file
  s390/hmcdrv: remove the redundant directory path in debug message

 Documentation/core-api/printk-formats.rst |  5 ++-
 drivers/s390/char/hmcdrv_dev.c            | 10 ++---
 fs/d_path.c                               | 51 +++++++++++++++++------
 include/linux/dcache.h                    |  1 +
 lib/vsprintf.c                            | 12 +++++-
 5 files changed, 58 insertions(+), 21 deletions(-)

-- 
2.17.1