vfs: atomic f_pos access in llseek()

Commit 9c225f26 ("vfs: atomic f_pos accesses as per POSIX") changed
several system calls to use fdget_pos() instead of fdget(), but missed
sys_llseek().  Fix it.
Signed-off-by: NEric Biggers <ebiggers3@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/read_write.c

@@ -307,7 +307,7 @@ SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
 		unsigned int, whence)
 {
 	int retval;
-	struct fd f = fdget(fd);
+	struct fd f = fdget_pos(fd);
 	loff_t offset;
 
 	if (!f.file)
@@ -327,7 +327,7 @@ SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
 			retval = 0;
 	}
 out_putf:
-	fdput(f);
+	fdput_pos(f);
 	return retval;
 }
 #endif