fbcon: Fix error paths in set_con2fb_map

This is a regressoin introduced in b07db395 ("fbcon: Ditch error
handling for con2fb_release_oldinfo"). I failed to realize what the if
(!err) checks. The mentioned commit was dropping the
con2fb_release_oldinfo() return value but the if (!err) was also
checking whether the con2fb_acquire_newinfo() function call above
failed or not.

Fix this with an early return statement.

Note that there's still a difference compared to the orginal state of
the code, the below lines are now also skipped on error:

	if (!search_fb_in_map(info_idx))
		info_idx = newidx;

These are only needed when we've actually thrown out an old fb_info
from the console mappings, which only happens later on.

Also move the fbcon_add_cursor_work() call into the same if block,
it's all protected by console_lock so doesn't matter when we set up
the blinking cursor delayed work anyway. This further simplifies the
control flow and allows us to ditch the found local variable.

v2: Clarify commit message (Javier)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Tested-by: Xingyuan Mo <hdthky0@gmail.com>
Fixes: b07db395 ("fbcon: Ditch error handling for con2fb_release_oldinfo")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Xingyuan Mo <hdthky0@gmail.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v5.19+

drivers/video/fbdev/core/fbcon.c

@@ -823,7 +823,7 @@ static int set_con2fb_map(int unit, int newidx, int user)
 	int oldidx = con2fb_map[unit];
 	struct fb_info *info = fbcon_registered_fb[newidx];
 	struct fb_info *oldinfo = NULL;
-	int found, err = 0, show_logo;
+	int err = 0, show_logo;
 
 	WARN_CONSOLE_UNLOCKED();
 
@@ -841,26 +841,25 @@ static int set_con2fb_map(int unit, int newidx, int user)
 	if (oldidx != -1)
 		oldinfo = fbcon_registered_fb[oldidx];
 
-	found = search_fb_in_map(newidx);
-
-	if (!err && !found) {
+	if (!search_fb_in_map(newidx)) {
 		err = con2fb_acquire_newinfo(vc, info, unit);
-		if (!err)
-			con2fb_map[unit] = newidx;
+		if (err)
+			return err;
+
+		con2fb_map[unit] = newidx;
+		fbcon_add_cursor_work(info);
 	}
 
 	/*
 	 * If old fb is not mapped to any of the consoles,
 	 * fbcon should release it.
 	 */
-	if (!err && oldinfo && !search_fb_in_map(oldidx))
+	if (oldinfo && !search_fb_in_map(oldidx))
 		con2fb_release_oldinfo(vc, oldinfo, info);
 
 	show_logo = (fg_console == 0 && !user &&
 			 logo_shown != FBCON_LOGO_DONTSHOW);
 
-	if (!found)
-		fbcon_add_cursor_work(info);
 	con2fb_map_boot[unit] = newidx;
 	con2fb_init_display(vc, info, unit, show_logo);