On Tue, Jun 15, 2021 at 6:54 PM Jia He [off-list ref] wrote:

Background
==========
Linus suggested printing full path for file instead of printing

the full
the file

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.

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

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

kasprintf()

After commenting on patch 1, I suggest you to always build with `make W=1 ...`

Changelog
=========
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 (4):
  fs: introduce helper d_path_unsafe()
  lib/vsprintf.c: make '%pD' print full path for file
  lib/test_printf.c: split write-beyond-buffer check in two
  lib/test_printf.c: add test cases for '%pD'

 Documentation/core-api/printk-formats.rst |  5 +-
 fs/d_path.c                               | 83 ++++++++++++++++++++++-
 include/linux/dcache.h                    |  1 +
 lib/test_printf.c                         | 31 ++++++++-
 lib/vsprintf.c                            | 37 ++++++++--
 5 files changed, 148 insertions(+), 9 deletions(-)

--
2.17.1

-- 
With Best Regards,
Andy Shevchenko