mm: memcontrol: fix cannot alloc the maximum memcg ID

The idr_alloc() does not include @max ID. So in the current
implementation, the maximum memcg ID is 65534 instead of 65535. It
seems a bug. So fix this.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Muchun Song <[e-mail]>
Cc: Alex Shi <[e-mail]>
Cc: Anna Schumaker <[e-mail]>
Cc: Chao Yu <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Cc: Fam Zheng <[e-mail]>
Cc: Jaegeuk Kim <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Kari Argillander <[e-mail]>
Cc: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Qi Zheng <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Theodore Ts'o <[e-mail]>
Cc: Trond Myklebust <[e-mail]>
Cc: Vladimir Davydov <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Wei Yang <[e-mail]>
Cc: Xiongchun Duan <[e-mail]>
Cc: Yang Shi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/memcontrol.c

···
 		return ERR_PTR(error);
 
 	memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
-				 1, MEM_CGROUP_ID_MAX,
-				 GFP_KERNEL);
+				 1, MEM_CGROUP_ID_MAX + 1, GFP_KERNEL);
 	if (memcg->id.id < 0) {
 		error = memcg->id.id;
 		goto fail;