ipc: delete seq_max field in struct ipc_ids

This field is only used to reset the ids seq number if it exceeds the
smaller of INT_MAX/SEQ_MULTIPLIER and USHRT_MAX, and can therefore be
moved out of the structure and into its own macro.  Since each
ipc_namespace contains a table of 3 pointers to struct ipc_ids we can
save space in instruction text:

   text    data     bss     dec     hex filename
  56232    2348      24   58604    e4ec ipc/built-in.o
  56216    2348      24   58588    e4dc ipc/built-in.o-after
Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com>
Reviewed-by: NJonathan Gonzalez <jgonzalez@linets.cl>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: NManfred Spraul <manfred@colorfullife.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/ipc_namespace.h

@@ -21,7 +21,6 @@ struct user_namespace;
 struct ipc_ids {
 	int in_use;
 	unsigned short seq;
-	unsigned short seq_max;
 	struct rw_semaphore rwsem;
 	struct idr ipcs_idr;
 	int next_id;

ipc/util.c

@@ -139,19 +139,10 @@ __initcall(ipc_init);
  */
 void ipc_init_ids(struct ipc_ids *ids)
 {
-	init_rwsem(&ids->rwsem);
-
 	ids->in_use = 0;
 	ids->seq = 0;
 	ids->next_id = -1;
-	{
-		int seq_limit = INT_MAX/SEQ_MULTIPLIER;
-		if (seq_limit > USHRT_MAX)
-			ids->seq_max = USHRT_MAX;
-		 else
-			ids->seq_max = seq_limit;
-	}
-
+	init_rwsem(&ids->rwsem);
 	idr_init(&ids->ipcs_idr);
 }
 
@@ -304,7 +295,7 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
 
 	if (next_id < 0) {
 		new->seq = ids->seq++;
-		if (ids->seq > ids->seq_max)
+		if (ids->seq > IPCID_SEQ_MAX)
 			ids->seq = 0;
 	} else {
 		new->seq = ipcid_to_seqx(next_id);

ipc/util.h

@@ -100,6 +100,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
 
 #define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
 #define ipcid_to_seqx(id) ((id) / SEQ_MULTIPLIER)
+#define IPCID_SEQ_MAX min_t(int, INT_MAX/SEQ_MULTIPLIER, USHRT_MAX)
 
 /* must be called with ids->rwsem acquired for writing */
 int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);