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>

1 files changed, 63 insertions, 0 deletions

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;
+}