tools lib fs: Add helper to find mounted file systems

In preparation for adding tracefs for perf to use, create a findfs
helper utility that find_debugfs uses instead of hard coding the search
in the code. This will allow for a find_tracefs to be used as well.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20150202193552.735023362@goodmis.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

5 files changed, 94 insertions, 54 deletions

diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
index 36c08b1f4afb..22b2f15d7255 100644
--- a/tools/lib/api/Makefile
+++ b/tools/lib/api/Makefile
@@ -9,11 +9,13 @@ LIB_H=
 LIB_OBJS=
 
 LIB_H += fs/debugfs.h
+LIB_H += fs/findfs.h
 LIB_H += fs/fs.h
 # See comment below about piggybacking...
 LIB_H += fd/array.h
 
 LIB_OBJS += $(OUTPUT)fs/debugfs.o
+LIB_OBJS += $(OUTPUT)fs/findfs.o
 LIB_OBJS += $(OUTPUT)fs/fs.o
 # XXX piggybacking here, need to introduce libapikfd, or rename this
 # to plain libapik.a and make it have it all api goodies
diff --git a/tools/lib/api/fs/debugfs.c b/tools/lib/api/fs/debugfs.c
index d21d4d6b4fd2..91e1668348ce 100644
--- a/tools/lib/api/fs/debugfs.c
+++ b/tools/lib/api/fs/debugfs.c
@@ -20,58 +20,21 @@ static const char * const debugfs_known_mountpoints[] = {
 
 static bool debugfs_found;
 
-/* verify that a mountpoint is actually a debugfs instance */
-
-static int debugfs_valid_mountpoint(const char *debugfs)
-{
-        struct statfs st_fs;
-
-        if (statfs(debugfs, &st_fs) < 0)
-                return -ENOENT;
-        else if ((long)st_fs.f_type != (long)DEBUGFS_MAGIC)
-                return -ENOENT;
-
-        return 0;
-}
-
 /* find the path to the mounted debugfs */
 const char *debugfs_find_mountpoint(void)
 {
-        const char * const *ptr;
-        char type[100];
-        FILE *fp;
+        const char *ret;
 
         if (debugfs_found)
                 return (const char *)debugfs_mountpoint;
 
-        ptr = debugfs_known_mountpoints;
-        while (*ptr) {
-                if (debugfs_valid_mountpoint(*ptr) == 0) {
-                        debugfs_found = true;
-                        strcpy(debugfs_mountpoint, *ptr);
-                        return debugfs_mountpoint;
-                }
-                ptr++;
-        }
+        ret = find_mountpoint("debugfs", (long) DEBUGFS_MAGIC,
+                              debugfs_mountpoint, PATH_MAX + 1,
+                              debugfs_known_mountpoints);
+        if (ret)
+                debugfs_found = true;
 
-        /* give up and parse /proc/mounts */
-        fp = fopen("/proc/mounts", "r");
-        if (fp == NULL)
-                return NULL;
-
-        while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
-                      debugfs_mountpoint, type) == 2) {
-                if (strcmp(type, "debugfs") == 0)
-                        break;
-        }
-        fclose(fp);
-
-        if (strcmp(type, "debugfs") != 0)
-                return NULL;
-
-        debugfs_found = true;
-
-        return debugfs_mountpoint;
+        return ret;
 }
 
 /* mount the debugfs somewhere if it's not mounted */
diff --git a/tools/lib/api/fs/debugfs.h b/tools/lib/api/fs/debugfs.h
index 77bb36a95b07..1074ac81358e 100644
--- a/tools/lib/api/fs/debugfs.h
+++ b/tools/lib/api/fs/debugfs.h
@@ -1,16 +1,7 @@
 #ifndef __API_DEBUGFS_H__
 #define __API_DEBUGFS_H__
 
-#define _STR(x) #x
-#define STR(x) _STR(x)
-
-/*
- * On most systems <limits.h> would have given us this, but  not on some systems
- * (e.g. GNU/Hurd).
- */
-#ifndef PATH_MAX
-#define PATH_MAX 4096
-#endif
+#include "findfs.h"
 
 #ifndef DEBUGFS_MAGIC
 #define DEBUGFS_MAGIC          0x64626720
diff --git a/tools/lib/api/fs/findfs.c b/tools/lib/api/fs/findfs.c
new file mode 100644
index 000000000000..49946cb6d7af
--- /dev/null
+++ b/tools/lib/api/fs/findfs.c
@@ -0,0 +1,63 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+
+#include "findfs.h"
+
+/* verify that a mountpoint is actually the type we want */
+
+int valid_mountpoint(const char *mount, long magic)
+{
+        struct statfs st_fs;
+
+        if (statfs(mount, &st_fs) < 0)
+                return -ENOENT;
+        else if ((long)st_fs.f_type != magic)
+                return -ENOENT;
+
+        return 0;
+}
+
+/* find the path to a mounted file system */
+const char *find_mountpoint(const char *fstype, long magic,
+                            char *mountpoint, int len,
+                            const char * const *known_mountpoints)
+{
+        const char * const *ptr;
+        char format[128];
+        char type[100];
+        FILE *fp;
+
+        if (known_mountpoints) {
+                ptr = known_mountpoints;
+                while (*ptr) {
+                        if (valid_mountpoint(*ptr, magic) == 0) {
+                                strncpy(mountpoint, *ptr, len - 1);
+                                mountpoint[len-1] = 0;
+                                return mountpoint;
+                        }
+                        ptr++;
+                }
+        }
+
+        /* give up and parse /proc/mounts */
+        fp = fopen("/proc/mounts", "r");
+        if (fp == NULL)
+                return NULL;
+
+        snprintf(format, 128, "%%*s %%%ds %%99s %%*s %%*d %%*d\n", len);
+
+        while (fscanf(fp, format, mountpoint, type) == 2) {
+                if (strcmp(type, fstype) == 0)
+                        break;
+        }
+        fclose(fp);
+
+        if (strcmp(type, fstype) != 0)
+                return NULL;
+
+        return mountpoint;
+}
diff --git a/tools/lib/api/fs/findfs.h b/tools/lib/api/fs/findfs.h
new file mode 100644
index 000000000000..9e7d876791e1
--- /dev/null
+++ b/tools/lib/api/fs/findfs.h
@@ -0,0 +1,21 @@
+#ifndef __API_FINDFS_H__
+#define __API_FINDFS_H__
+
+#define _STR(x) #x
+#define STR(x) _STR(x)
+
+/*
+ * On most systems <limits.h> would have given us this, but  not on some systems
+ * (e.g. GNU/Hurd).
+ */
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
+const char *find_mountpoint(const char *fstype, long magic,
+                            char *mountpoint, int len,
+                            const char * const *known_mountpoints);
+
+int valid_mountpoint(const char *mount, long magic);
+
+#endif /* __API_FINDFS_H__ */