vt/fbcon: fix background color on line feed

Another addendum to commit c9e587abfdec2c2aaa55fab83bcb4972e2f84f9b
("vt: fix background color on line feed").

fbcon still was not doing the right thing (read: continued to do old
behavior). fbcon_clear() seems to clear the new line (e.g. where your new
prompt appears after doing echo -en "\e[42mfoo\n"), while scr_memsetw clears
the previous one only (where "foo" appears). So just temporarily set the
video_erase_char to the scrl_erase_char so that fbcon_clear does the right
thing.

Signed-off-by: Jan Engelhardt <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/console/fbcon.c

···
 	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
 	struct display *p = &fb_display[vc->vc_num];
 	int scroll_partial = info->flags & FBINFO_PARTIAL_PAN_OK;
+	unsigned short saved_ec;
+	int ret;
 
 	if (fbcon_is_inactive(vc, info))
 		return -EINVAL;
···
 	 * ++Andrew: Only use ypan on hardware text mode when scrolling the
 	 *           whole screen (prevents flicker).
 	 */
+
+	saved_ec = vc->vc_video_erase_char;
+	vc->vc_video_erase_char = vc->vc_scrl_erase_char;
+
+	ret = 0;
 
 	switch (dir) {
 	case SM_UP:
···
 							(b - count)),
 				    vc->vc_scrl_erase_char,
 				    vc->vc_size_row * count);
-			return 1;
+			ret = 1;
 			break;
 
 		case SCROLL_WRAP_MOVE:
···
 							(b - count)),
 				    vc->vc_scrl_erase_char,
 				    vc->vc_size_row * count);
-			return 1;
+			ret = 1;
+			break;
 		}
 		break;
 
···
 							t),
 				    vc->vc_scrl_erase_char,
 				    vc->vc_size_row * count);
-			return 1;
+			ret = 1;
 			break;
 
 		case SCROLL_WRAP_MOVE:
···
 							t),
 				    vc->vc_scrl_erase_char,
 				    vc->vc_size_row * count);
-			return 1;
+			ret = 1;
+			break;
 		}
+		break;
 	}
-	return 0;
+	vc->vc_video_erase_char = saved_ec;
+	return ret;
 }