ipc: add sysctl to specify desired next object id

[karo-tx-linux.git] / ipc / util.c

diff --git a/ipc/util.c b/ipc/util.c
index 72fd0785ac948b4c3813a2aac8f463ea41e7955f..a961e469433ade3cba9dcf7ad51f39d193694527 100644 (file)
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -122,6 +122,7 @@ void ipc_init_ids(struct ipc_ids *ids)
 
        ids->in_use = 0;
        ids->seq = 0;
+       ids->next_id = -1;
        {
                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
                if (seq_limit > USHRT_MAX)
@@ -252,6 +253,7 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
        kuid_t euid;
        kgid_t egid;
        int id, err;
+       int next_id = ids->next_id;
 
        if (size > IPCMNI)
                size = IPCMNI;
@@ -264,7 +266,8 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
        rcu_read_lock();
        spin_lock(&new->lock);
 
-       err = idr_get_new(&ids->ipcs_idr, new, &id);
+       err = idr_get_new_above(&ids->ipcs_idr, new,
+                               (next_id < 0) ? 0 : ipcid_to_idx(next_id), &id);
        if (err) {
                spin_unlock(&new->lock);
                rcu_read_unlock();
@@ -277,9 +280,14 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
        new->cuid = new->uid = euid;
        new->gid = new->cgid = egid;
 
-       new->seq = ids->seq++;
-       if(ids->seq > ids->seq_max)
-               ids->seq = 0;
+       if (next_id < 0) {
+               new->seq = ids->seq++;
+               if(ids->seq > ids->seq_max)
+                       ids->seq = 0;
+       } else {
+               new->seq = ipcid_to_seqx(next_id);
+               ids->next_id = -1;
+       }
 
        new->id = ipc_buildid(id, new->seq);
        return id;