tracing/core: make the per cpu trace files in per cpu directories

Impact: restructure the VFS layout of per CPU trace buffers

The per cpu trace files are all in a single directory:
/debug/tracing/per_cpu. In case of a large number of cpu, the
content of this directory becomes messy so we create now one
directory per cpu inside /debug/tracing/per_cpu which contain
each their own trace_pipe and trace files.

Ie:

 /debug/tracing$ ls -R per_cpu
 per_cpu:
 cpu0  cpu1

 per_cpu/cpu0:
 trace  trace_pipe

 per_cpu/cpu1:
 trace  trace_pipe

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 11 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d8d899f3bd6f..bdaf60d3d337 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3061,28 +3061,31 @@ struct dentry *tracing_dentry_percpu(void)
 static void tracing_init_debugfs_percpu(long cpu)
 {
         struct dentry *d_percpu = tracing_dentry_percpu();
-        struct dentry *entry;
-        /* strlen(trace_pipe) + MAX(log10(cpu)) + '\0' */
-        char filename[17];
+        struct dentry *entry, *d_cpu;
+        /* strlen(cpu) + MAX(log10(cpu)) + '\0' */
+        char cpu_dir[7];
 
         if (cpu > 999 || cpu < 0)
                 return;
 
-        /* per cpu trace_pipe */
-        sprintf(filename, "trace_pipe%ld", cpu);
+        sprintf(cpu_dir, "cpu%ld", cpu);
+        d_cpu = debugfs_create_dir(cpu_dir, d_percpu);
+        if (!d_cpu) {
+                pr_warning("Could not create debugfs '%s' entry\n", cpu_dir);
+                return;
+        }
 
-        entry = debugfs_create_file(filename, 0444, d_percpu,
+        /* per cpu trace_pipe */
+        entry = debugfs_create_file("trace_pipe", 0444, d_cpu,
                                 (void *) cpu, &tracing_pipe_fops);
         if (!entry)
-                pr_warning("Could not create debugfs '%s' entry\n", filename);
+                pr_warning("Could not create debugfs 'trace_pipe' entry\n");
 
         /* per cpu trace */
-        sprintf(filename, "trace%ld", cpu);
-
-        entry = debugfs_create_file(filename, 0444, d_percpu,
+        entry = debugfs_create_file("trace", 0444, d_cpu,
                                 (void *) cpu, &tracing_fops);
         if (!entry)
-                pr_warning("Could not create debugfs '%s' entry\n", filename);
+                pr_warning("Could not create debugfs 'trace' entry\n");
 }
 
 #ifdef CONFIG_FTRACE_SELFTEST