I think line 929 should be changed back to static u8 gm = 01;

So PS3_GM01 will be always the first folder mounted and PS3_GAME will be the last.

Your current code will mount PS3_GAME only for the first game. After that all games will follow the behavior described above.

Or maybe this code:

void map_app_home(const char *path)
{
	unmap_app_home();

	// remap app_home for multi-game discs
	char *mpath = (char *)malloc(strlen(path) + sizeof("/PS3_GAME") + 1);
	if(mpath)
	{
		sprintf(mpath, "%s/PS3_GM%02i", path, gm);
		if(not_exists(mpath))
		{
			sys_map_path("/app_home", path);

			sprintf(mpath, "%s/PS3_GM01", path);
			gm = isDir(mpath) ? 01 : 00; // reset gm to 00 if the game is not a multi-game disc
		}
		else
		{
			sys_map_path(APP_HOME_DIR, mpath); gm++;
		}

		free(mpath);
	}
}

I think line 929 should be changed back to static u8 gm = 01;

So PS3_GM01 will be always the first folder mounted and PS3_GAME will be the last.

Your current code will mount PS3_GAME only for the first game. After that all games will follow the behavior described above.

PS3_GAME -> PS3_GM01 -> PS3_GM.. is the order the XMB uses for multi-game discs, so i don't think it should be changed
my code does exactly that - it mounts PS3_GAME first, then cycles through GM folders, until it runs out of them, and then mounts PS3_GAME again

(correct me if i'm wrong, i'm new to C)

Yes your code does it right for the first game. After that the variable gm never return to 00.
So when a new game is mounted, the variable gm return to 01 (for non multi-game discs or mounts the next folder in the cycle if the new game is also a multi-game disc).

The code above fixes this behavior, except when the new game is also a multi-game disc.

why should it return to 0? if GMXX doesn't exist, it will simply follow the "if(not_exists(mpath))" condition and mount /app_home to /dev_bdvd. adding another check just creates redundancy imo

oh, i think i finally understand what you mean