mount: Factor out detached mountpoint opening

The difficulty is that this code is required in both -- pie
and non-pie contexts.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/util-pie.h

@@ -59,4 +59,5 @@ static inline int recv_fd(int sock)
 	return fd;
 }
 
+int open_detach_mount(char *dir);
 #endif /* __CR_UTIL_NET_H__ */

mount.c

@@ -15,6 +15,7 @@
 #include "crtools.h"
 #include "asm/types.h"
 #include "util.h"
+#include "util-pie.h"
 #include "log.h"
 #include "mount.h"
 #include "proc_parse.h"
@@ -289,20 +290,7 @@ static DIR *open_mountpoint(struct mount_info *pm)
 		goto out;
 	}
 
-	fd = open(mnt_path, O_RDONLY | O_DIRECTORY);
-	if (fd < 0)
-		pr_perror("Can't open %s\n", mnt_path);
-
-	if (umount2(mnt_path, MNT_DETACH)) {
-		pr_perror("Can't umount %s", mnt_path);
-		goto out;
-	}
-
-	if (rmdir(mnt_path)) {
-		pr_perror("Can't remove the directory %s", mnt_path);
-		goto out;
-	}
-
+	fd = open_detach_mount(mnt_path);
 	if (fd < 0)
 		goto out;
 

pie/parasite.c

@@ -237,22 +237,11 @@ static int parasite_get_proc_fd()
 
 	if (sys_mount("proc", proc_mountpoint, "proc", MS_MGC_VAL, NULL)) {
 		pr_err("mount failed\n");
-		goto out_rmdir;
-	}
-
-	fd = sys_open(proc_mountpoint, O_RDONLY, 0);
-
-	if (sys_umount2(proc_mountpoint, MNT_DETACH)) {
-		pr_err("Can't umount procfs\n");
-		return -1;
-	}
-
-out_rmdir:
-	if (sys_rmdir(proc_mountpoint)) {
-		pr_err("Can't remove directory\n");
+		sys_rmdir(proc_mountpoint);
 		return -1;
 	}
 
+	fd = open_detach_mount(proc_mountpoint);
 out_send_fd:
 	if (fd < 0)
 		return fd;

pie/util.c

 #include <sys/socket.h>
 #include <sys/un.h>
+#include <sys/mount.h>
 
 #include <errno.h>
 
@@ -7,7 +8,7 @@
 #include "asm/string.h"
 #include "asm/types.h"
 #include "syscall.h"
-
+#include "log.h"
 #include "util-pie.h"
 
 static void scm_fdset_init_chunk(struct scm_fdset *fdset, int nr_fds)
@@ -149,3 +150,28 @@ int recv_fds(int sock, int *fds, int nr_fds, struct fd_opts *opts)
 	return 0;
 }
 
+int open_detach_mount(char *dir)
+{
+	int fd;
+
+	fd = sys_open(dir, O_RDONLY | O_DIRECTORY, 0);
+	if (fd < 0)
+		pr_perror("Can't open directory");
+
+	if (sys_umount2(dir, MNT_DETACH)) {
+		pr_perror("Can't detach mount");
+		goto err_close;
+	}
+
+	if (sys_rmdir(dir)) {
+		pr_perror("Can't remove tmp dir");
+		goto err_close;
+	}
+
+	return fd;
+
+err_close:
+	if (fd >= 0)
+		sys_close(fd);
+	return -1;
+}