take rlimit check to callers of expand_files()

... except for one in android, where the check is different
and already done in caller.  No need to recalculate rlimit
many times in alloc_fd() either.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fcntl.c

@@ -64,6 +64,9 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
 	if (unlikely(oldfd == newfd))
 		return -EINVAL;
 
+	if (newfd >= rlimit(RLIMIT_NOFILE))
+		return -EMFILE;
+
 	spin_lock(&files->file_lock);
 	err = expand_files(files, newfd);
 	file = fcheck(oldfd);

fs/file.c

@@ -251,13 +251,6 @@ int expand_files(struct files_struct *files, int nr)
 
 	fdt = files_fdtable(files);
 
-	/*
-	 * N.B. For clone tasks sharing a files structure, this test
-	 * will limit the total number of files that can be opened.
-	 */
-	if (nr >= rlimit(RLIMIT_NOFILE))
-		return -EMFILE;
-
 	/* Do we need to expand? */
 	if (nr < fdt->max_fds)
 		return 0;
@@ -431,6 +424,7 @@ int alloc_fd(unsigned start, unsigned flags)
 {
 	struct files_struct *files = current->files;
 	unsigned int fd;
+	unsigned end = rlimit(RLIMIT_NOFILE);
 	int error;
 	struct fdtable *fdt;
 
@@ -444,6 +438,14 @@ int alloc_fd(unsigned start, unsigned flags)
 	if (fd < fdt->max_fds)
 		fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
 
+	/*
+	 * N.B. For clone tasks sharing a files structure, this test
+	 * will limit the total number of files that can be opened.
+	 */
+	error = -EMFILE;
+	if (fd >= end)
+		goto out;
+
 	error = expand_files(files, fd);
 	if (error < 0)
 		goto out;