sysvipc: make get_maxid O(1) again

[mirror_ubuntu-bionic-kernel.git] / ipc / util.c

diff --git a/ipc/util.c b/ipc/util.c
index e09bf76610efb347afc36f91d636250ee0b7b2ea..ff045fec8d835549d35faf54742be3f15f1b356a 100644 (file)
--- 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;
+       }
 }
 
 /**