kernel/linux.git/tools/lib/api/fs, branch v6.6.131

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

tools api fs: Cache cgroupfs mount point

2021-02-17T18:09:08+00:00

Currently it parses the /proc file everytime it opens a file in the cgroupfs. Save the last result to avoid it (assuming it won't be changed between the accesses). Signed-off-by: Namhyung Kim Cc: Alexander Shishkin Cc: Andi Kleen Cc: Ian Rogers Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lore.kernel.org/lkml/20201216090556.813996-3-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Diet cgroupfs_find_mountpoint()

2021-02-17T18:08:32+00:00

Reduce the number of buffers and hopefully make it more efficient. :) Signed-off-by: Namhyung Kim Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andi Kleen Cc: Ian Rogers Cc: Mark Rutland Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lore.kernel.org/lkml/20201216090556.813996-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Prefer cgroup v1 path in cgroupfs_find_mountpoint()

2021-02-17T18:06:22+00:00

The cgroupfs_find_mountpoint() looks up the /proc/mounts file to find a directory for the given cgroup subsystem. It keeps both cgroup v1 and v2 path since there's a possibility of the mixed hierarchly. But we can simply use v1 path if it's found as it will override the v2 hierarchy. Signed-off-by: Namhyung Kim Cc: Alexander Shishkin Cc: Andi Kleen Cc: Ian Rogers Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lore.kernel.org/lkml/20201216090556.813996-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Make xxx__mountpoint() more scalable

2020-04-16T15:19:12+00:00

The xxx_mountpoint() interface provided by fs.c finds mount points for common pseudo filesystems. The first time xxx_mountpoint() is invoked, it scans the mount table (/proc/mounts) looking for a match. If found, it is cached. The price to scan /proc/mounts is paid once if the mount is found. When the mount point is not found, subsequent calls to xxx_mountpoint() scan /proc/mounts over and over again. There is no caching. This causes a scaling issue in perf record with hugeltbfs__mountpoint(). The function is called for each process found in synthesize__mmap_events(). If the machine has thousands of processes and if the /proc/mounts has many entries this could cause major overhead in perf record. We have observed multi-second slowdowns on some configurations. As an example on a laptop: Before: $ sudo umount /dev/hugepages $ strace -e trace=openat -o /tmp/tt perf record -a ls $ fgrep mounts /tmp/tt 285 After: $ sudo umount /dev/hugepages $ strace -e trace=openat -o /tmp/tt perf record -a ls $ fgrep mounts /tmp/tt 1 One could argue that the non-caching in case the moint point is not found is intentional. That way subsequent calls may discover a moint point if the sysadmin mounts the filesystem. But the same argument could be made against caching the mount point. It could be unmounted causing errors. It all depends on the intent of the interface. This patch assumes it is expected to scan /proc/mounts once. The patch documents the caching behavior in the fs.h header file. An alternative would be to just fix perf record. But it would solve the problem with hugetlbs__mountpoint() but there could be similar issues (possibly down the line) with other xxx_mountpoint() calls in perf or other tools. Signed-off-by: Stephane Eranian Reviewed-by: Ian Rogers Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andrey Zhizhikin Cc: Kan Liang Cc: Kefeng Wang Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Petr Mladek Cc: Thomas Gleixner Link: http://lore.kernel.org/lkml/20200402154357.107873-3-irogers@google.com Signed-off-by: Ian Rogers Signed-off-by: Arnaldo Carvalho de Melo