ipc: store ipcs into IDRs

This patch introduces ipcs storage into IDRs. The main changes are:
  . This ipc_ids structure is changed: the entries array is changed into a
    root idr structure.
  . The grow_ary() routine is removed: it is not needed anymore when adding
    an ipc structure, since we are now using the IDR facility.
  . The ipc_rmid() routine interface is changed:
       . there is no need for this routine to return the pointer passed in as
         argument: it is now declared as a void
       . since the id is now part of the kern_ipc_perm structure, no need to
         have it as an argument to the routine

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 118 insertions, 148 deletions

diff --git a/ipc/util.c b/ipc/util.c
index 44e5135aee47..2a205875d277 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -129,23 +129,16 @@ __initcall(ipc_init);
 /**
  *      ipc_init_ids            -       initialise IPC identifiers
  *      @ids: Identifier set
- *      @size: Number of identifiers
  *
- *      Given a size for the ipc identifier range (limited below IPCMNI)
- *      set up the sequence range to use then allocate and initialise the
- *      array itself. 
+ *      Set up the sequence range to use for the ipc identifier range (limited
+ *      below IPCMNI) then initialise the ids idr.
  */
  
-void ipc_init_ids(struct ipc_ids* ids, int size)
+void ipc_init_ids(struct ipc_ids *ids)
 {
-        int i;
-
         mutex_init(&ids->mutex);
 
-        if(size > IPCMNI)
-                size = IPCMNI;
         ids->in_use = 0;
-        ids->max_id = -1;
         ids->seq = 0;
         {
                 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
@@ -155,17 +148,7 @@ void ipc_init_ids(struct ipc_ids* ids, int size)
                         ids->seq_max = seq_limit;
         }
 
-        ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
-                                     sizeof(struct ipc_id_ary));
-
-        if(ids->entries == NULL) {
-                printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
-                size = 0;
-                ids->entries = &ids->nullentry;
-        }
-        ids->entries->size = size;
-        for(i=0;i<size;i++)
-                ids->entries->p[i] = NULL;
+        idr_init(&ids->ipcs_idr);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -209,72 +192,73 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
  *      @key: The key to find
  *      
  *      Requires ipc_ids.mutex locked.
- *      Returns the identifier if found or -1 if not.
+ *      Returns the LOCKED pointer to the ipc structure if found or NULL
+ *      if not.
+ *      If key is found ipc contains its ipc structure
  */
  
-int ipc_findkey(struct ipc_ids* ids, key_t key)
+struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 {
-        int id;
-        struct kern_ipc_perm* p;
-        int max_id = ids->max_id;
+        struct kern_ipc_perm *ipc;
+        int next_id;
+        int total;
 
-        /*
-         * rcu_dereference() is not needed here
-         * since ipc_ids.mutex is held
-         */
-        for (id = 0; id <= max_id; id++) {
-                p = ids->entries->p[id];
-                if(p==NULL)
+        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
+                ipc = idr_find(&ids->ipcs_idr, next_id);
+
+                if (ipc == NULL)
                         continue;
-                if (key == p->key)
-                        return id;
+
+                if (ipc->key != key) {
+                        total++;
+                        continue;
+                }
+
+                ipc_lock_by_ptr(ipc);
+                return ipc;
         }
-        return -1;
+
+        return NULL;
 }
 
-/*
- * Requires ipc_ids.mutex locked
+/**
+ *      ipc_get_maxid   -       get the last assigned id
+ *      @ids: IPC identifier set
+ *
+ *      Called with ipc_ids.mutex held.
  */
-static int grow_ary(struct ipc_ids* ids, int newsize)
-{
-        struct ipc_id_ary* new;
-        struct ipc_id_ary* old;
-        int i;
-        int size = ids->entries->size;
-
-        if(newsize > IPCMNI)
-                newsize = IPCMNI;
-        if(newsize <= size)
-                return newsize;
-
-        new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
-                            sizeof(struct ipc_id_ary));
-        if(new == NULL)
-                return size;
-        new->size = newsize;
-        memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size);
-        for(i=size;i<newsize;i++) {
-                new->p[i] = NULL;
-        }
-        old = ids->entries;
 
-        /*
-         * Use rcu_assign_pointer() to make sure the memcpyed contents
-         * of the new array are visible before the new array becomes visible.
-         */
-        rcu_assign_pointer(ids->entries, new);
+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;
 
-        __ipc_fini_ids(ids, old);
-        return newsize;
+        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;
 }
 
 /**
  *      ipc_addid       -       add an IPC identifier
  *      @ids: IPC identifier set
  *      @new: new IPC permission set
- *      @size: new size limit for the id array
+ *      @size: limit for the number of used ids
  *
- *      Add an entry 'new' to the IPC arrays. The permissions object is
+ *      Add an entry 'new' to the IPC idr. The permissions object is
  *      initialised and the first free entry is set up and the id assigned
  *      is returned. The list is returned in a locked state on success.
  *      On failure the list is not locked and -1 is returned.
@@ -284,23 +268,23 @@ static int grow_ary(struct ipc_ids* ids, int newsize)
  
 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
-        int id;
-
-        size = grow_ary(ids,size);
+        int id, err;
 
         /*
          * rcu_dereference()() is not needed here since
          * ipc_ids.mutex is held
          */
-        for (id = 0; id < size; id++) {
-                if(ids->entries->p[id] == NULL)
-                        goto found;
-        }
-        return -1;
-found:
+        if (size > IPCMNI)
+                size = IPCMNI;
+
+        if (ids->in_use >= size)
+                return -1;
+
+        err = idr_get_new(&ids->ipcs_idr, new, &id);
+        if (err)
+                return -1;
+
         ids->in_use++;
-        if (id > ids->max_id)
-                ids->max_id = id;
 
         new->cuid = new->uid = current->euid;
         new->gid = new->cgid = current->egid;
@@ -313,48 +297,32 @@ found:
         new->deleted = 0;
         rcu_read_lock();
         spin_lock(&new->lock);
-        ids->entries->p[id] = new;
         return id;
 }
 
 /**
  *      ipc_rmid        -       remove an IPC identifier
  *      @ids: identifier set
- *      @id: Identifier to remove
+ *      @id: ipc perm structure containing the identifier to remove
  *
  *      The identifier must be valid, and in use. The kernel will panic if
  *      fed an invalid identifier. The entry is removed and internal
- *      variables recomputed. The object associated with the identifier
- *      is returned.
- *      ipc_ids.mutex and the spinlock for this ID is hold before this function
- *      is called, and remain locked on the exit.
+ *      variables recomputed.
+ *      ipc_ids.mutex and the spinlock for this ID are held before this
+ *      function is called, and remain locked on the exit.
  */
  
-struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
+void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
-        struct kern_ipc_perm* p;
-        int lid = id % SEQ_MULTIPLIER;
-        BUG_ON(lid >= ids->entries->size);
+        int lid = ipcp->id % SEQ_MULTIPLIER;
+
+        idr_remove(&ids->ipcs_idr, lid);
 
-        /* 
-         * do not need a rcu_dereference()() here to force ordering
-         * on Alpha, since the ipc_ids.mutex is held.
-         */     
-        p = ids->entries->p[lid];
-        ids->entries->p[lid] = NULL;
-        BUG_ON(p==NULL);
         ids->in_use--;
 
-        if (lid == ids->max_id) {
-                do {
-                        lid--;
-                        if(lid == -1)
-                                break;
-                } while (ids->entries->p[lid] == NULL);
-                ids->max_id = lid;
-        }
-        p->deleted = 1;
-        return p;
+        ipcp->deleted = 1;
+
+        return;
 }
 
 /**
@@ -613,33 +581,26 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
  * if in the future ipc_get() is used by other places without ipc_ids.mutex
  * down, then ipc_get() needs read memery barriers as ipc_lock() does.
  */
-struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
+struct kern_ipc_perm *ipc_get(struct ipc_ids *ids, int id)
 {
-        struct kern_ipc_perm* out;
+        struct kern_ipc_perm *out;
         int lid = id % SEQ_MULTIPLIER;
-        if(lid >= ids->entries->size)
-                return NULL;
-        out = ids->entries->p[lid];
+        out = idr_find(&ids->ipcs_idr, lid);
         return out;
 }
 
-struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
+struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 {
-        struct kern_ipc_perm* out;
+        struct kern_ipc_perm *out;
         int lid = id % SEQ_MULTIPLIER;
-        struct ipc_id_ary* entries;
 
         rcu_read_lock();
-        entries = rcu_dereference(ids->entries);
-        if(lid >= entries->size) {
-                rcu_read_unlock();
-                return NULL;
-        }
-        out = entries->p[lid];
-        if(out == NULL) {
+        out = idr_find(&ids->ipcs_idr, lid);
+        if (out == NULL) {
                 rcu_read_unlock();
                 return NULL;
         }
+
         spin_lock(&out->lock);
         
         /* ipc_rmid() may have already freed the ID while ipc_lock
@@ -650,6 +611,7 @@ struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
                 rcu_read_unlock();
                 return NULL;
         }
+
         return out;
 }
 
@@ -707,27 +669,30 @@ struct ipc_proc_iter {
         struct ipc_proc_iface *iface;
 };
 
-static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
+/*
+ * This routine locks the ipc structure found at least at position pos.
+ */
+struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
+                                        loff_t *new_pos)
 {
-        struct ipc_proc_iter *iter = s->private;
-        struct ipc_proc_iface *iface = iter->iface;
-        struct kern_ipc_perm *ipc = it;
-        loff_t p;
-        struct ipc_ids *ids;
+        struct kern_ipc_perm *ipc;
+        int total, id;
 
-        ids = iter->ns->ids[iface->ids];
+        total = 0;
+        for (id = 0; id < pos && total < ids->in_use; id++) {
+                ipc = idr_find(&ids->ipcs_idr, id);
+                if (ipc != NULL)
+                        total++;
+        }
 
-        /* If we had an ipc id locked before, unlock it */
-        if (ipc && ipc != SEQ_START_TOKEN)
-                ipc_unlock(ipc);
+        if (total >= ids->in_use)
+                return NULL;
 
-        /*
-         * p = *pos - 1 (because id 0 starts at position 1)
-         *          + 1 (because we increment the position by one)
-         */
-        for (p = *pos; p <= ids->max_id; p++) {
-                if ((ipc = ipc_lock(ids, p)) != NULL) {
-                        *pos = p + 1;
+        for ( ; pos < IPCMNI; pos++) {
+                ipc = idr_find(&ids->ipcs_idr, pos);
+                if (ipc != NULL) {
+                        *new_pos = pos + 1;
+                        ipc_lock_by_ptr(ipc);
                         return ipc;
                 }
         }
@@ -736,6 +701,19 @@ static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
         return NULL;
 }
 
+static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
+{
+        struct ipc_proc_iter *iter = s->private;
+        struct ipc_proc_iface *iface = iter->iface;
+        struct kern_ipc_perm *ipc = it;
+
+        /* If we had an ipc id locked before, unlock it */
+        if (ipc && ipc != SEQ_START_TOKEN)
+                ipc_unlock(ipc);
+
+        return sysvipc_find_ipc(iter->ns->ids[iface->ids], *pos, pos);
+}
+
 /*
  * File positions: pos 0 -> header, pos n -> ipc id + 1.
  * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
@@ -744,8 +722,6 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 {
         struct ipc_proc_iter *iter = s->private;
         struct ipc_proc_iface *iface = iter->iface;
-        struct kern_ipc_perm *ipc;
-        loff_t p;
         struct ipc_ids *ids;
 
         ids = iter->ns->ids[iface->ids];
@@ -765,13 +741,7 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
                 return SEQ_START_TOKEN;
 
         /* Find the (pos-1)th ipc */
-        for (p = *pos - 1; p <= ids->max_id; p++) {
-                if ((ipc = ipc_lock(ids, p)) != NULL) {
-                        *pos = p + 1;
-                        return ipc;
-                }
-        }
-        return NULL;
+        return sysvipc_find_ipc(ids, *pos - 1, pos);
 }
 
 static void sysvipc_proc_stop(struct seq_file *s, void *it)