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. This series is based on Al Viro's d_path() cleanup patches [1] which lifted the inner lockless loop into a new helper. 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 ========= v2: - 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 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 Link: https://lkml.org/lkml/2021/5/18/1260 [1] 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 | 122 ++++++++++++++++++++-- include/linux/dcache.h | 1 + lib/test_printf.c | 54 ++++++++-- lib/vsprintf.c | 40 ++++++- 5 files changed, 199 insertions(+), 23 deletions(-) -- 2.17.1
