[PATCH v5 0/4] make '%pD' print the full path of file

Background
==========
Linus suggested printing the full path of 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 it doesn't take any seqlock/spinlock.

This series is based on Al Viro's d_path cleanup patches [1] which
lifted the inner lockless loop into a new helper. 

Link: https://lkml.org/lkml/2021/5/18/1260 [1]

Test
====
The cases I tested:
1. print '%pD' with full path of ext4 file
2. mount a ext4 filesystem upon a ext4 filesystem, and print the file
   with '%pD'
3. all test_print selftests, including the new '%14pD' '%-14pD'
4. kasnprintf
   
Changelog
=========
v5:
- remove the RFC tag
- refine the commit msg/comments(by Petr, Andy)
- make using_scratch_space a new parameter of the test case 

v4:
- don't support spec.precision anymore for '%pD'
- add Rasmus's patch into this series
 
v3:
- implement new d_path_unsafe to use [buf, end] instead of stack space for
  filling bytes (by Matthew)
- add new test cases for '%pD'
- drop patch "hmcdrv: remove the redundant directory path" before removing rfc.

v2: 
- implement new d_path_fast based on Al Viro's patches
- add check_pointer check (by Petr)
- change the max full path size to 256 in stack space

v1: https://lkml.org/lkml/2021/5/8/122


Jia He (3):
  fs: introduce helper d_path_unsafe()
  lib/vsprintf.c: make '%pD' print the full path of file
  lib/test_printf.c: add test cases for '%pD'

Rasmus Villemoes (1):
  lib/test_printf.c: split write-beyond-buffer check in two

 Documentation/core-api/printk-formats.rst |   5 +-
 fs/d_path.c                               | 104 +++++++++++++++++++++-
 include/linux/dcache.h                    |   1 +
 lib/test_printf.c                         |  54 ++++++++---
 lib/vsprintf.c                            |  40 ++++++++-
 5 files changed, 184 insertions(+), 20 deletions(-)

-- 
2.17.1