linux.git/tools/lib/api/fs, branch v6.18.21

tool api fs: Correctly encode errno for read/write open failures

2024-12-09T20:52:42+00:00

Switch from returning -1 to -errno so that callers can determine types
of failure.

Reviewed-by: Namhyung Kim 
Signed-off-by: Ian Rogers 
Acked-by: Arnaldo Carvalho de Melo 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Athira Rajeev 
Cc: Ben Gainey 
Cc: Colin Ian King 
Cc: Dominique Martinet 
Cc: Ilkka Koskinen 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jiri Olsa 
Cc: Kan Liang 
Cc: Mark Rutland 
Cc: Oliver Upton 
Cc: Paran Lee 
Cc: Peter Zijlstra 
Cc: Steinar H. Gunderson 
Cc: Steven Rostedt (VMware) 
Cc: Thomas Falcon 
Cc: Weilin Wang 
Cc: Yang Jihong 
Cc: Yang Li 
Cc: Ze Gao 
Cc: Zixian Cai 
Cc: zhaimingbing 
Link: https://lore.kernel.org/r/20241118225345.889810-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

perf list: Give clues if failed to open tracing events directory

2024-08-01T15:11:33+00:00

When executing the command "perf list", I met "Error: failed to open
tracing events directory" twice, the first reason is that there is no
"/sys/kernel/tracing/events" directory due to it does not enable the
kernel tracing infrastructure with CONFIG_FTRACE, the second reason
is that there is no root privileges.

Add the error string to tell the users what happened and what should
to do, and also call put_tracing_file() to free events_path a little
later to avoid messy code in the error message.

At the same time, just remove the redundant "/" of the file path in
the function get_tracing_file(), otherwise it shows something like
"/sys/kernel/tracing//events".

Before:

  $ ./perf list
  Error: failed to open tracing events directory

After:

(1) Without CONFIG_FTRACE

  $ ./perf list
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: No such file or directory

(2) With CONFIG_FTRACE but no root privileges

  $ ./perf list
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: Permission denied

Committer testing:

Redirect stdout to null to quickly test the patch:

Before:

  $ perf list > /dev/null
  Error: failed to open tracing events directory
  $

After:

  $ perf list > /dev/null
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: Permission denied
  $

Signed-off-by: Tiezhu Yang 
Tested-by: Arnaldo Carvalho de Melo 
Cc: Ingo Molnar 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/lkml/20240730062301.23244-3-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Avoid reading whole file for a 1 byte bool

2023-11-30T22:25:19+00:00

sysfs__read_bool() used the first byte from a fully read file into a
string. It then looked at the first byte's value. Avoid doing this and
just read the first byte.

Signed-off-by: Ian Rogers 
Acked-by: Namhyung Kim 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Athira Jajeev 
Cc: Changbin Du 
Cc: Colin Ian King 
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: German Gomez 
Cc: Guilherme Amadio 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jiri Olsa 
Cc: K Prateek Nayak 
Cc: Kajol Jain 
Cc: Kan Liang 
Cc: Leo Yan 
Cc: Li Dong 
Cc: Liam Howlett 
Cc: Mark Rutland 
Cc: Masami Hiramatsu (Google) 
Cc: Miguel Ojeda 
Cc: Ming Wang 
Cc: Nick Terrell 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Sandipan Das 
Cc: Sean Christopherson 
Cc: Steinar H. Gunderson 
Cc: Vincent Whitchurch 
Cc: Wenyu Liu 
Cc: Yang Jihong 
Link: https://lore.kernel.org/r/20231127220902.1315692-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Switch filename__read_str to use io.h

2023-11-30T22:25:19+00:00

filename__read_str() has its own string reading code that allocates
memory before reading into it. The memory allocated is sized at BUFSIZ
that is 8kb. Most strings are short and so most of this 8kb is wasted.

Refactor io__getline(), as io__getdelim(), so that the newline character
can be configurable and ignored in the case of filename__read_str().

Code like build_caches_for_cpu() in perf's header.c will read many strings
and hold them in a data structure, in this case multiple strings per
cache level per CPU.

Using io.h's io__getline() avoids the wasted memory as strings are
temporarily read into a buffer on the stack before being copied to a
buffer that grows 128 bytes at a time and is never sized larger than the
string.

For a 16 hyperthread system the memory consumption of "perf record
true" is reduced by 180kb, primarily through saving memory when
reading the cache information.

Signed-off-by: Ian Rogers 
Acked-by: Namhyung Kim 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Athira Jajeev 
Cc: Changbin Du 
Cc: Colin Ian King 
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: German Gomez 
Cc: Guilherme Amadio 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jiri Olsa 
Cc: K Prateek Nayak 
Cc: Kajol Jain 
Cc: Kan Liang 
Cc: Leo Yan 
Cc: Li Dong 
Cc: Liam Howlett 
Cc: Mark Rutland 
Cc: Masami Hiramatsu (Google) 
Cc: Miguel Ojeda 
Cc: Ming Wang 
Cc: Nick Terrell 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Sandipan Das 
Cc: Sean Christopherson 
Cc: Steinar H. Gunderson 
Cc: Vincent Whitchurch 
Cc: Wenyu Liu 
Cc: Yang Jihong 
Link: https://lore.kernel.org/r/20231127220902.1315692-5-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: More thread safety for global filesystem variables

2023-06-14T02:40:32+00:00

Multiple threads, such as with "perf top", may race to initialize a
file system path like hugetlbfs. The racy initialization of the path
leads to at least memory leaks. To avoid this initialize each fs for
reading the mount point path with pthread_once.

Mounting the file system may also be racy, so introduce a mutex over
the function. This does mean that the path is being accessed with and
without a mutex, which is inherently racy but hopefully benign,
especially as there are fewer callers to fs__mount.

Remove the fs__entries by directly using global variables, this was
done as no argument like the index can be passed to the init once
routine.

Issue found and tested with "perf top" and address sanitizer.

Signed-off-by: Ian Rogers 
Cc: Adrian Hunter 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230609224004.180988-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Dynamically allocate cgroupfs mount point cache, removing 4128 bytes from .bss

2023-05-28T13:25:25+00:00

Move the cgroupfs_cache_entry 4128 byte array out of .bss.

Signed-off-by: Ian Rogers 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: K Prateek Nayak 
Cc: Kan Liang 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Masami Hiramatsu 
Cc: Namhyung Kim 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Ross Zwisler 
Cc: Sean Christopherson 
Cc: Steven Rostedt (VMware) 
Cc: Tiezhu Yang 
Cc: Yang Jihong 
Link: https://lore.kernel.org/r/20230526183401.2326121-15-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs tracing_path: Remove two unused MAX_PATH paths

2023-05-28T13:23:00+00:00

tracing_mnt was set but never written. tracing_events_path was set and
read on errors paths, but its value is exactly tracing_path with a
"/events" appended, so we can derive the value in the error
paths. There appears to have been a missing "/" when
tracing_events_path was initialized.

Signed-off-by: Ian Rogers 
Link: https://lore.kernel.org/r/20230526183401.2326121-8-irogers@google.com
Cc: K Prateek Nayak 
Cc: Ravi Bangoria 
Cc: Mark Rutland 
Cc: Ross Zwisler 
Cc: Steven Rostedt (Google) 
Cc: Sean Christopherson 
Cc: Yang Jihong 
Cc: Peter Zijlstra 
Cc: Adrian Hunter 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Masami Hiramatsu (Google) 
Cc: Namhyung Kim 
Cc: Leo Yan 
Cc: Andi Kleen 
Cc: Alexander Shishkin 
Cc: Kan Liang 
Cc: Tiezhu Yang 
Cc: Ingo Molnar 
Cc: Paolo Bonzini 
Cc: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Avoid large static PATH_MAX arrays

2023-05-28T13:22:40+00:00

Change struct fs to have a pointer to a dynamically allocated array
rather than an array. This reduces the size of fs__entries from 24,768
bytes to 240 bytes. Read paths into a stack allocated array and
strdup. Fix off-by-1 fscanf %s in fs__read_mounts caught by
address sanitizer.

Signed-off-by: Ian Rogers 
Link: https://lore.kernel.org/r/20230526183401.2326121-7-irogers@google.com
Cc: K Prateek Nayak 
Cc: Ravi Bangoria 
Cc: Mark Rutland 
Cc: Ross Zwisler 
Cc: Steven Rostedt (Google) 
Cc: Sean Christopherson 
Cc: Yang Jihong 
Cc: Peter Zijlstra 
Cc: Adrian Hunter 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Masami Hiramatsu (Google) 
Cc: Namhyung Kim 
Cc: Leo Yan 
Cc: Andi Kleen 
Cc: Alexander Shishkin 
Cc: Kan Liang 
Cc: Tiezhu Yang 
Cc: Ingo Molnar 
Cc: Paolo Bonzini 
Cc: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tracing: Always use canonical ftrace path

2023-02-18T19:34:09+00:00

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com

Acked-by: Masami Hiramatsu (Google) 
Reviewed-by: Mukesh Ojha 
Signed-off-by: Ross Zwisler 
Signed-off-by: Steven Rostedt (Google)

tools lib api fs tracing_path: Add scandir alphasort

2022-11-15T13:24:09+00:00

tracing_events__opendir() allows iteration over files in
/tracing/events but with an arbitrary sort order.

Add a scandir alternative where the results are alphabetically sorted.

Signed-off-by: Ian Rogers 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Caleb Biggers 
Cc: Jiri Olsa 
Cc: Kajol Jain 
Cc: Kan Liang 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Perry Taylor 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Rob Herring 
Cc: Sandipan Das 
Cc: Stephane Eranian 
Cc: Weilin Wang 
Cc: Xin Gao 
Cc: Xing Zhengjun 
Link: http://lore.kernel.org/lkml/20221114210723.2749751-4-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo