3 files changed, 32 insertions, 33 deletions

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index d7cf3a850853..b5630c8eb2f3 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -19,6 +19,7 @@ struct ipc_ids {
 	bool tables_initialized;
 	struct rw_semaphore rwsem;
 	struct idr ipcs_idr;
+	int max_id;
 #ifdef CONFIG_CHECKPOINT_RESTORE
 	int next_id;
 #endif
diff --git a/ipc/util.c b/ipc/util.c
index e09bf76610ef..ff045fec8d83 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -122,6 +122,7 @@ int ipc_init_ids(struct ipc_ids *ids)
 		return err;
 	idr_init(&ids->ipcs_idr);
 	ids->tables_initialized = true;
+	ids->max_id = -1;
 #ifdef CONFIG_CHECKPOINT_RESTORE
 	ids->next_id = -1;
 #endif
@@ -188,36 +189,6 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 	return NULL;
 }
 
-/**
- * ipc_get_maxid - get the last assigned id
- * @ids: ipc identifier set
- *
- * Called with ipc_ids.rwsem held.
- */
-int ipc_get_maxid(struct ipc_ids *ids)
-{
-	struct kern_ipc_perm *ipc;
-	int max_id = -1;
-	int total, id;
-
-	if (ids->in_use == 0)
-		return -1;
-
-	if (ids->in_use == IPCMNI)
-		return IPCMNI - 1;
-
-	/* Look for the last assigned id */
-	total = 0;
-	for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
-		ipc = idr_find(&ids->ipcs_idr, id);
-		if (ipc != NULL) {
-			max_id = id;
-			total++;
-		}
-	}
-	return max_id;
-}
-
 #ifdef CONFIG_CHECKPOINT_RESTORE
 /*
  * Specify desired id for next allocated IPC object.
@@ -313,6 +284,9 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
 	}
 
 	ids->in_use++;
+	if (id > ids->max_id)
+		ids->max_id = id;
+
 	new->id = ipc_buildid(id, ids, new);
 
 	return id;
@@ -459,6 +433,15 @@ void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 	ipc_kht_remove(ids, ipcp);
 	ids->in_use--;
 	ipcp->deleted = true;
+
+	if (unlikely(lid == ids->max_id)) {
+		do {
+			lid--;
+			if (lid == -1)
+				break;
+		} while (!idr_find(&ids->ipcs_idr, lid));
+		ids->max_id = lid;
+	}
 }
 
 /**
diff --git a/ipc/util.h b/ipc/util.h
index 0cd6201fe63a..89b8ec176fc4 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -13,6 +13,7 @@
 
 #include <linux/unistd.h>
 #include <linux/err.h>
+#include <linux/ipc_namespace.h>
 
 #define SEQ_MULTIPLIER	(IPCMNI)
 
@@ -99,9 +100,6 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
 /* must be called with ids->rwsem acquired for writing */
 int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
 
-/* must be called with ids->rwsem acquired for reading */
-int ipc_get_maxid(struct ipc_ids *);
-
 /* must be called with both locks acquired. */
 void ipc_rmid(struct ipc_ids *, struct kern_ipc_perm *);
 
@@ -111,6 +109,23 @@ void ipc_set_key_private(struct ipc_ids *, struct kern_ipc_perm *);
 /* must be called with ipcp locked */
 int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flg);
 
+/**
+ * ipc_get_maxid - get the last assigned id
+ * @ids: ipc identifier set
+ *
+ * Called with ipc_ids.rwsem held for reading.
+ */
+static inline int ipc_get_maxid(struct ipc_ids *ids)
+{
+	if (ids->in_use == 0)
+		return -1;
+
+	if (ids->in_use == IPCMNI)
+		return IPCMNI - 1;
+
+	return ids->max_id;
+}
+
 /*
  * For allocation that need to be freed by RCU.
  * Objects are reference counted, they start with reference count 1.