api.c: use /proc/self/mounts

Use /proc/self/mount instead of /proc/mounts, which is a symbolic link
to the former. The symbolic link creation can be traced back to Linux
Kernel commit 59c7572e82d6 ("proc: remove fs/proc/proc_misc.c"). Also,
the /proc/mounts are not available in the cases where the /proc is
mounted with subset=pid option.

As per kernel docs filesystems/procs.rst:
"subset=pid hides all top level files and directories in the procfs that
are not related to tasks."

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
(cherry picked from commit 16be308b037bbe11a54b692c227e160f1132eabe)

diff --git a/src/api.c b/src/api.c
index f7b6873aef4a8ca2c3d65192f0f0f4828f92c2ce..0874ca1d898a81d0594d27f8f98e5a2902e49f01 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -1385,9 +1385,9 @@ int cgroup_init(void)
        }
        controllers[i] = NULL;
 
-       proc_mount = fopen("/proc/mounts", "re");
+       proc_mount = fopen("/proc/self/mounts", "re");
        if (proc_mount == NULL) {
-               cgroup_err("Error: cannot open /proc/mounts: %s\n",
+               cgroup_err("Error: cannot open /proc/self/mounts: %s\n",
                                strerror(errno));
                last_errno = errno;
                ret = ECGOTHER;
@@ -1463,7 +1463,7 @@ static int cg_test_mounted_fs(void)
        char mntent_buff[4 * FILENAME_MAX];
        int ret = 1;
 
-       proc_mount = fopen("/proc/mounts", "re");
+       proc_mount = fopen("/proc/self/mounts", "re");
        if (proc_mount == NULL)
                return 0;