initramfs: use vfs_stat/lstat directly

sys_newlstat is a system call implementation that is meant for user
space, and that copies kernel-internal data structure to the user
format, which is not needed for in-kernel users.

Further, as we rearrange the system call implementation so we can extend
it with 64-bit time_t, the prototype for sys_newlstat changes.

This changes the initramfs code to use vfs_lstat directly, to get it out
of the way of the time_t changes, and make it slightly more efficient in
the process.  Along the same lines we also replace sys_stat and
sys_stat64 with vfs_stat.

Link: http://lkml.kernel.org/r/20170314214932.4052842-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/do_mounts.h

@@ -19,29 +19,15 @@ static inline int create_dev(char *name, dev_t dev)
 	return sys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));
 }
 
-#if BITS_PER_LONG == 32
 static inline u32 bstat(char *name)
 {
-	struct stat64 stat;
-	if (sys_stat64(name, &stat) != 0)
+	struct kstat stat;
+	if (vfs_stat(name, &stat) != 0)
 		return 0;
-	if (!S_ISBLK(stat.st_mode))
+	if (!S_ISBLK(stat.mode))
 		return 0;
-	if (stat.st_rdev != (u32)stat.st_rdev)
-		return 0;
-	return stat.st_rdev;
+	return stat.rdev;
 }
-#else
-static inline u32 bstat(char *name)
-{
-	struct stat stat;
-	if (sys_newstat(name, &stat) != 0)
-		return 0;
-	if (!S_ISBLK(stat.st_mode))
-		return 0;
-	return stat.st_rdev;
-}
-#endif
 
 #ifdef CONFIG_BLK_DEV_RAM