mount_entry: use statvfs

Use statvfs instead of parsing /proc/self/mountinfo to check for the
flags we need to and into the msbind mount flags.  This will be faster
and the code is cleaner.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 6789562efd54d98c1735be6527f5c89fdb7eeac2..072623bd8f3c3db45d0b449d580452b797da2220 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -36,6 +36,7 @@
 #include <pwd.h>
 #include <grp.h>
 #include <time.h>
+#include <sys/statvfs.h>
 
 #if HAVE_PTY_H
 #include <pty.h>
@@ -1952,49 +1953,12 @@ static char *get_field(char *src, int nfields)
        return p;
 }
 
-static unsigned long get_mount_flags(const char *path)
-{
-       FILE *f = fopen("/proc/self/mountinfo", "r");
-       char *line = NULL;
-       size_t len = 0;
-       unsigned long flags = 0;
-
-       if (!f) {
-               WARN("Failed to open /proc/self/mountinfo");
-               return 0;
-       }
-       while (getline(&line, &len, f) != -1) {
-               char *target, *opts, *p, *saveptr = NULL;
-               target = get_field(line, 4);
-               if (!target)
-                       continue;
-               opts = get_field(target, 2);
-               if (!opts)
-                       continue;
-               null_endofword(opts);
-               for (p = strtok_r(opts, ",", &saveptr); p;
-                       p = strtok_r(NULL, ",", &saveptr)) {
-                       if (strcmp(p, "ro") == 0)
-                               flags |= MS_RDONLY;
-                       else if (strcmp(p, "nodev") == 0)
-                               flags |= MS_NODEV;
-                       else if (strcmp(p, "nosuid") == 0)
-                               flags |= MS_NOSUID;
-                       else if (strcmp(p, "noexec") == 0)
-                               flags |= MS_NOEXEC;
-                       /* XXX todo - we'll have to deal with atime? */
-               }
-       }
-       free(line);
-       fclose(f);
-       return flags;
-}
-
 static int mount_entry(const char *fsname, const char *target,
                       const char *fstype, unsigned long mountflags,
                       const char *data, int optional)
 {
-       unsigned long extraflags;
+       struct statvfs sb;
+
        if (mount(fsname, target, fstype, mountflags & ~MS_REMOUNT, data)) {
                if (optional) {
                        INFO("failed to mount '%s' on '%s' (optional): %s", fsname,
@@ -2008,20 +1972,34 @@ static int mount_entry(const char *fsname, const char *target,
        }
 
        if ((mountflags & MS_REMOUNT) || (mountflags & MS_BIND)) {
-               extraflags = get_mount_flags(target);
-               DEBUG("flags was %lu, extraflags set to %lu", mountflags, extraflags);
-               if (!(mountflags & MS_REMOUNT) && (mountflags & MS_BIND)) {
-                       if (!(extraflags & ~mountflags))
-                               DEBUG("all mount flags match, skipping remount");
-                               goto skipremount;
+               DEBUG("remounting %s on %s to respect bind or remount options",
+                     fsname ? fsname : "(none)", target ? target : "(none)");
+
+               if (statvfs(fsname, &sb) == 0) {
+                       unsigned long required_flags = 0;
+                       if (sb.f_flag & MS_NOSUID)
+                               required_flags |= MS_NOSUID;
+                       if (sb.f_flag & MS_NODEV)
+                               required_flags |= MS_NODEV;
+                       if (sb.f_flag & MS_RDONLY)
+                               required_flags |= MS_RDONLY;
+                       if (sb.f_flag & MS_NOEXEC)
+                               required_flags |= MS_NOEXEC;
+                       DEBUG("(at remount) flags for %s was %lu, required extra flags are %lu", fsname, sb.f_flag, required_flags);
+                       /*
+                        * If this was a bind mount request, and required_flags
+                        * does not have any flags which are not already in
+                        * mountflags, then skip the remount
+                        */
+                       if (!(mountflags & MS_REMOUNT)) {
+                               if (!(required_flags & ~mountflags)) {
+                                       DEBUG("mountflags already was %lu, skipping remount",
+                                               mountflags);
+                                       goto skipremount;
+                               }
+                       }
+                       mountflags |= required_flags;
                }
-               mountflags |= extraflags;
-       }
-
-       if ((mountflags & MS_REMOUNT) || (mountflags & MS_BIND)) {
-               DEBUG("remounting %s on %s to respect bind or remount options %lu (extra %lu)",
-                     fsname ? fsname : "(none)",
-                     target ? target : "(none)", mountflags, extraflags);
 
                if (mount(fsname, target, fstype,
                          mountflags | MS_REMOUNT, data)) {