Add mount.c file for mount helpers functions

At moment only open_mnt_root is there, which is
needed for inotify restore.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Makefile

@@ -53,6 +53,7 @@ OBJS		+= netfilter.o
 OBJS		+= shmem.o
 OBJS		+= eventfd.o
 OBJS		+= eventpoll.o
+OBJS		+= mount.o
 
 DEPS		:= $(patsubst %.o,%.d,$(OBJS))
 

include/mount.h

+#ifndef MOUNT_H__
+#define MOUNT_H__
+
+struct proc_mountinfo;
+
+extern int open_mnt_root(unsigned int s_dev, struct proc_mountinfo *mntinfo, int nr_mntinfo);
+
+#endif /* MOUNT_H__ */

mount.c

+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <string.h>
+
+#include "types.h"
+#include "util.h"
+#include "mount.h"
+#include "proc_parse.h"
+
+/*
+ * Returns path for mount device @s_dev
+ *
+ * FIXME this is not sufficient in general
+ * since mount points can be overmounted but
+ * works for now.
+ */
+int open_mnt_root(unsigned int s_dev, struct proc_mountinfo *mntinfo, int nr_mntinfo)
+{
+	static int last = 0;
+	int i;
+
+again:
+	for (i = last; i < nr_mntinfo; i++) {
+		if (s_dev == mntinfo[i].s_dev) {
+			last = i;
+			return open(mntinfo[i].mnt_root, O_RDONLY);
+		}
+	}
+
+	if (last) {
+		last = 0;
+		goto again;
+	}
+
+	return -ENOENT;
+}