[PATCH v7 0/5] make '%pD' print the full path of file

From: Jia He
Date: Wed Jul 14 2021 - 21:14:22 EST


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_unsafe() which is similar to d_path() except it doesn't take any
seqlock/spinlock.

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. kasprintf

TODO
====
I plan to do the followup work after '%pD' behavior is changed.
- s390/hmcdrv: remove the redundant directory path in printing string.
- fs/iomap: simplify the iomap_swapfile_fail() with '%pD'.
- simplify the string printing when file_path() is invoked(in some
cases, not all).
- change the previous '%pD[2,3,4]' to '%pD'

Changelog
=========
v7:
- rebase to 5.14-rc1 after Al Viro d_path cleanup series was merged
- add patch1/5 to fix the kernel doc validator issue
- refine the commit msg, add more comments for the smp_load_acquire in
prepend_name_with_len()

v6(new v2):https://lkml.org/lkml/2021/6/23/44
- refine the commit msg/comments (Andy)
- pass the validator check by "make C=1 W=1"
- add the R-b for patch 4/4 from Andy

v5(new v1): https://lkml.org/lkml/2021/6/22/680
- remove the RFC tag
- refine the commit msg/comments(by Petr, Andy)
- make using_scratch_space a new parameter of the test case

RFCv4:
- don't support spec.precision anymore for '%pD'
- add Rasmus's patch into this series

RFCv3:
- 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.

RFCv2:
- 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

RFCv1: https://lkml.org/lkml/2021/5/8/122

Jia He (4):
d_path: fix Kernel doc validator complaints
d_path: 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 | 7 +-
fs/d_path.c | 123 ++++++++++++++++++++--
include/linux/dcache.h | 1 +
lib/test_printf.c | 54 ++++++++--
lib/vsprintf.c | 40 ++++++-
5 files changed, 202 insertions(+), 23 deletions(-)

--
2.17.1