fix pivot umount algorithm

Make a function and fix bad parameter to umount.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index e003852f89ee057bb50d679c6bcb0845d0a932c6..eb4e8467f95d85100e6664d98f53c69ef00078e7 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -458,67 +458,30 @@ static int setup_rootfs_pivot_root_cb(char *buffer, void *data)
        return 0;
 }
 
-static int setup_rootfs_pivot_root(const char *rootfs, const char *pivotdir)
+static int umount_oldrootfs(const char *oldrootfs)
 {
        char path[MAXPATHLEN];
        void *cbparm[2];
        struct lxc_list mountlist, *iterator;
        int ok, still_mounted, last_still_mounted;
-       int remove_pivotdir = 0;
-
-       /* change into new root fs */
-       if (chdir(rootfs)) {
-               SYSERROR("can't chdir to new rootfs '%s'", rootfs);
-               return -1;
-       }
-
-       if (!pivotdir)
-               pivotdir = "oldrootfs";
-
-       /* create a default mountpoint if none specified */
-       snprintf(path, sizeof(path), "%s/%s", rootfs, pivotdir);
-
-       if (access(path, F_OK)) {
-
-               if (mkdir_p(path, 0755)) {
-                       SYSERROR("failed to create pivotdir '%s'", path);
-                       return -1;
-               }
-
-               remove_pivotdir = 1;
-               DEBUG("created '%s' directory", path);
-       }
-
-       DEBUG("mountpoint for old rootfs is '%s'", path);
-
-       /* pivot_root into our new root fs */
-
-       if (pivot_root(".", path)) {
-               SYSERROR("pivot_root syscall failed");
-               return -1;
-       }
-
-       if (chdir("/")) {
-               SYSERROR("can't chdir to / after pivot_root");
-               return -1;
-       }
-
-       DEBUG("pivot_root syscall to '%s' successful", pivotdir);
 
        /* read and parse /proc/mounts in old root fs */
        lxc_list_init(&mountlist);
 
-       snprintf(path, sizeof(path), "%s/", pivotdir);
+       /* oldrootfs is on the top tree directory now */
+       snprintf(path, sizeof(path), "/%s", oldrootfs);
        cbparm[0] = &mountlist;
-       cbparm[1] = strdup(path);
 
+       cbparm[1] = strdup(path);
        if (!cbparm[1]) {
                SYSERROR("strdup failed");
                return -1;
        }
 
-       snprintf(path, sizeof(path), "/%s/proc/mounts", pivotdir);
-       ok = lxc_file_for_each_line(path, setup_rootfs_pivot_root_cb, &cbparm);
+       snprintf(path, sizeof(path), "%s/proc/mounts", oldrootfs);
+
+       ok = lxc_file_for_each_line(path,
+                                   setup_rootfs_pivot_root_cb, &cbparm);
        if (ok < 0) {
                SYSERROR("failed to read or parse mount list '%s'", path);
                return -1;
@@ -562,16 +525,55 @@ static int setup_rootfs_pivot_root(const char *rootfs, const char *pivotdir)
                WARN("failed to unmount '%s'", (char *)iterator->elem);
        }
 
-       /* umount old root fs; if some other mount points are still
-        * there, we won't be able to umount it, so we have to do
-        * that in a lazy way otherwise the container will always
-        * fail to start
-        */
-       if (umount2(pivotdir, MNT_DETACH)) {
-               SYSERROR("could not unmount old rootfs");
+       return 0;
+}
+
+static int setup_rootfs_pivot_root(const char *rootfs, const char *pivotdir)
+{
+       char path[MAXPATHLEN];
+       int remove_pivotdir = 0;
+
+       /* change into new root fs */
+       if (chdir(rootfs)) {
+               SYSERROR("can't chdir to new rootfs '%s'", rootfs);
+               return -1;
+       }
+
+       if (!pivotdir)
+               pivotdir = "oldrootfs";
+
+       /* create a default mountpoint if none specified */
+       snprintf(path, sizeof(path), "%s/%s", rootfs, pivotdir);
+
+       if (access(path, F_OK)) {
+
+               if (mkdir_p(path, 0755)) {
+                       SYSERROR("failed to create pivotdir '%s'", path);
+                       return -1;
+               }
+
+               remove_pivotdir = 1;
+               DEBUG("created '%s' directory", path);
+       }
+
+       DEBUG("mountpoint for old rootfs is '%s'", path);
+
+       /* pivot_root into our new root fs */
+       if (pivot_root(".", path)) {
+               SYSERROR("pivot_root syscall failed");
                return -1;
        }
-       DEBUG("umounted '%s'", pivotdir);
+
+       if (chdir("/")) {
+               SYSERROR("can't chdir to / after pivot_root");
+               return -1;
+       }
+
+       DEBUG("pivot_root syscall to '%s' successful", rootfs);
+
+       /* we switch from absolute path to relative path */
+       if (umount_oldrootfs(pivotdir))
+               return -1;
 
        /* remove temporary mount point, we don't consider the removing
         * as fatal */
@@ -579,6 +581,7 @@ static int setup_rootfs_pivot_root(const char *rootfs, const char *pivotdir)
                WARN("can't remove mountpoint '%s': %m", pivotdir);
 
        INFO("pivoted to '%s'", rootfs);
+
        return 0;
 }
 
@@ -606,7 +609,7 @@ static int setup_rootfs(const struct lxc_rootfs *rootfs)
        DEBUG("mounted '%s' on '%s'", rootfs->path, mpath);
 
        if (setup_rootfs_pivot_root(mpath, rootfs->pivot)) {
-               ERROR("failed to pivot_root to '%s'", rootfs->pivot);
+               ERROR("failed to setup pivot root");
                return -1;
        }