X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=lib%2Fidr.c;h=1cac726c44bc17cc6fa1a7b5ab6358279a0c9a5d;hb=a1004d8e3d463012f231bab104325ecb15637f78;hp=80ba06f29d36a4d76596cecb3df5313b2d77d85e;hpb=944ca05c7b4972f2ebf37262e0f4933d178ad6db;p=safe%2Fjmp%2Flinux-2.6

diff --git a/lib/idr.c b/lib/idr.c
index 80ba06f..1cac726 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -6,6 +6,8 @@
  * Modified by George Anzinger to reuse immediately and to use
  * find bit instructions.  Also removed _irq on spinlocks.
  *
+ * Modified by Nadia Derbey to make it RCU safe.
+ *
  * Small id to pointer translation service.
  *
  * It uses a radix tree like structure as a sparse array indexed
@@ -50,6 +52,19 @@ static struct idr_layer *get_from_free_list(struct idr *idp)
 	return(p);
 }
 
+static void idr_layer_rcu_free(struct rcu_head *head)
+{
+	struct idr_layer *layer;
+
+	layer = container_of(head, struct idr_layer, rcu_head);
+	kmem_cache_free(idr_layer_cache, layer);
+}
+
+static inline void free_layer(struct idr_layer *p)
+{
+	call_rcu(&p->rcu_head, idr_layer_rcu_free);
+}
+
 /* only called when idp->lock is held */
 static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
 {
@@ -96,7 +111,7 @@ static void idr_mark_full(struct idr_layer **pa, int id)
  * @gfp_mask:	memory allocation flags
  *
  * This function should be called prior to locking and calling the
- * following function.  It preallocates enough memory to satisfy
+ * idr_get_new* functions. It preallocates enough memory to satisfy
  * the worst possible allocation.
  *
  * If the system is REALLY out of memory this function returns 0,
@@ -106,7 +121,7 @@ int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
 {
 	while (idp->id_free_cnt < IDR_FREE_MAX) {
 		struct idr_layer *new;
-		new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
+		new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
 		if (new == NULL)
 			return (0);
 		move_to_free_list(idp, new);
@@ -170,7 +185,8 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
 			new = get_from_free_list(idp);
 			if (!new)
 				return -1;
-			p->ary[m] = new;
+			new->layer = l-1;
+			rcu_assign_pointer(p->ary[m], new);
 			p->count++;
 		}
 		pa[l--] = p;
@@ -195,6 +211,7 @@ build_up:
 	if (unlikely(!p)) {
 		if (!(p = get_from_free_list(idp)))
 			return -1;
+		p->layer = 0;
 		layers = 1;
 	}
 	/*
@@ -203,8 +220,14 @@ build_up:
 	 */
 	while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
 		layers++;
-		if (!p->count)
+		if (!p->count) {
+			/* special case: if the tree is currently empty,
+			 * then we grow the tree by moving the top node
+			 * upwards.
+			 */
+			p->layer++;
 			continue;
+		}
 		if (!(new = get_from_free_list(idp))) {
 			/*
 			 * The allocation failed.  If we built part of
@@ -222,11 +245,12 @@ build_up:
 		}
 		new->ary[0] = p;
 		new->count = 1;
+		new->layer = layers-1;
 		if (p->bitmap == IDR_FULL)
 			__set_bit(0, &new->bitmap);
 		p = new;
 	}
-	idp->top = p;
+	rcu_assign_pointer(idp->top, p);
 	idp->layers = layers;
 	v = sub_alloc(idp, &id, pa);
 	if (v == IDR_NEED_TO_GROW)
@@ -245,7 +269,8 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
 		 * Successfully found an empty slot.  Install the user
 		 * pointer and mark the slot full.
 		 */
-		pa[0]->ary[id & IDR_MASK] = (struct idr_layer *)ptr;
+		rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
+				(struct idr_layer *)ptr);
 		pa[0]->count++;
 		idr_mark_full(pa, id);
 	}
@@ -256,7 +281,7 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
 /**
  * idr_get_new_above - allocate new idr entry above or equal to a start id
  * @idp: idr handle
- * @ptr: pointer you want associated with the ide
+ * @ptr: pointer you want associated with the id
  * @start_id: id to start search at
  * @id: pointer to the allocated handle
  *
@@ -267,7 +292,7 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
  * and go back to the idr_pre_get() call.  If the idr is full, it will
  * return -ENOSPC.
  *
- * @id returns a value in the range 0 ... 0x7fffffff
+ * @id returns a value in the range @starting_id ... 0x7fffffff
  */
 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
 {
@@ -288,7 +313,7 @@ EXPORT_SYMBOL(idr_get_new_above);
 /**
  * idr_get_new - allocate new idr entry
  * @idp: idr handle
- * @ptr: pointer you want associated with the ide
+ * @ptr: pointer you want associated with the id
  * @id: pointer to the allocated handle
  *
  * This is the allocate id function.  It should be called with any
@@ -328,6 +353,7 @@ static void sub_remove(struct idr *idp, int shift, int id)
 	struct idr_layer *p = idp->top;
 	struct idr_layer **pa[MAX_LEVEL];
 	struct idr_layer ***paa = &pa[0];
+	struct idr_layer *to_free;
 	int n;
 
 	*paa = NULL;
@@ -343,13 +369,18 @@ static void sub_remove(struct idr *idp, int shift, int id)
 	n = id & IDR_MASK;
 	if (likely(p != NULL && test_bit(n, &p->bitmap))){
 		__clear_bit(n, &p->bitmap);
-		p->ary[n] = NULL;
+		rcu_assign_pointer(p->ary[n], NULL);
+		to_free = NULL;
 		while(*paa && ! --((**paa)->count)){
-			move_to_free_list(idp, **paa);
+			if (to_free)
+				free_layer(to_free);
+			to_free = **paa;
 			**paa-- = NULL;
 		}
 		if (!*paa)
 			idp->layers = 0;
+		if (to_free)
+			free_layer(to_free);
 	} else
 		idr_remove_warning(id);
 }
@@ -362,22 +393,34 @@ static void sub_remove(struct idr *idp, int shift, int id)
 void idr_remove(struct idr *idp, int id)
 {
 	struct idr_layer *p;
+	struct idr_layer *to_free;
 
 	/* Mask off upper bits we don't use for the search. */
 	id &= MAX_ID_MASK;
 
 	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
 	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
-	    idp->top->ary[0]) {  // We can drop a layer
-
+	    idp->top->ary[0]) {
+		/*
+		 * Single child at leftmost slot: we can shrink the tree.
+		 * This level is not needed anymore since when layers are
+		 * inserted, they are inserted at the top of the existing
+		 * tree.
+		 */
+		to_free = idp->top;
 		p = idp->top->ary[0];
-		idp->top->bitmap = idp->top->count = 0;
-		move_to_free_list(idp, idp->top);
-		idp->top = p;
+		rcu_assign_pointer(idp->top, p);
 		--idp->layers;
+		to_free->bitmap = to_free->count = 0;
+		free_layer(to_free);
 	}
 	while (idp->id_free_cnt >= IDR_FREE_MAX) {
 		p = get_from_free_list(idp);
+		/*
+		 * Note: we don't call the rcu callback here, since the only
+		 * layers that fall into the freelist are those that have been
+		 * preallocated.
+		 */
 		kmem_cache_free(idr_layer_cache, p);
 	}
 	return;
@@ -406,6 +449,7 @@ void idr_remove_all(struct idr *idp)
 
 	n = idp->layers * IDR_BITS;
 	p = idp->top;
+	rcu_assign_pointer(idp->top, NULL);
 	max = 1 << n;
 
 	id = 0;
@@ -418,15 +462,12 @@ void idr_remove_all(struct idr *idp)
 
 		id += 1 << n;
 		while (n < fls(id)) {
-			if (p) {
-				memset(p, 0, sizeof *p);
-				move_to_free_list(idp, p);
-			}
+			if (p)
+				free_layer(p);
 			n += IDR_BITS;
 			p = *--paa;
 		}
 	}
-	idp->top = NULL;
 	idp->layers = 0;
 }
 EXPORT_SYMBOL(idr_remove_all);
@@ -453,25 +494,30 @@ EXPORT_SYMBOL(idr_destroy);
  * return indicates that @id is not valid or you passed %NULL in
  * idr_get_new().
  *
- * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
  */
 void *idr_find(struct idr *idp, int id)
 {
 	int n;
 	struct idr_layer *p;
 
-	n = idp->layers * IDR_BITS;
-	p = idp->top;
+	p = rcu_dereference(idp->top);
+	if (!p)
+		return NULL;
+	n = (p->layer+1) * IDR_BITS;
 
 	/* Mask off upper bits we don't use for the search. */
 	id &= MAX_ID_MASK;
 
 	if (id >= (1 << n))
 		return NULL;
+	BUG_ON(n == 0);
 
 	while (n > 0 && p) {
 		n -= IDR_BITS;
-		p = p->ary[(id >> n) & IDR_MASK];
+		BUG_ON(n != p->layer*IDR_BITS);
+		p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
 	}
 	return((void *)p);
 }
@@ -504,7 +550,7 @@ int idr_for_each(struct idr *idp,
 	struct idr_layer **paa = &pa[0];
 
 	n = idp->layers * IDR_BITS;
-	p = idp->top;
+	p = rcu_dereference(idp->top);
 	max = 1 << n;
 
 	id = 0;
@@ -512,7 +558,7 @@ int idr_for_each(struct idr *idp,
 		while (n > 0 && p) {
 			n -= IDR_BITS;
 			*paa++ = p;
-			p = p->ary[(id >> n) & IDR_MASK];
+			p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
 		}
 
 		if (p) {
@@ -533,6 +579,52 @@ int idr_for_each(struct idr *idp,
 EXPORT_SYMBOL(idr_for_each);
 
 /**
+ * idr_get_next - lookup next object of id to given id.
+ * @idp: idr handle
+ * @id:  pointer to lookup key
+ *
+ * Returns pointer to registered object with id, which is next number to
+ * given id.
+ */
+
+void *idr_get_next(struct idr *idp, int *nextidp)
+{
+	struct idr_layer *p, *pa[MAX_LEVEL];
+	struct idr_layer **paa = &pa[0];
+	int id = *nextidp;
+	int n, max;
+
+	/* find first ent */
+	n = idp->layers * IDR_BITS;
+	max = 1 << n;
+	p = rcu_dereference(idp->top);
+	if (!p)
+		return NULL;
+
+	while (id < max) {
+		while (n > 0 && p) {
+			n -= IDR_BITS;
+			*paa++ = p;
+			p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
+		}
+
+		if (p) {
+			*nextidp = id;
+			return p;
+		}
+
+		id += 1 << n;
+		while (n < fls(id)) {
+			n += IDR_BITS;
+			p = *--paa;
+		}
+	}
+	return NULL;
+}
+
+
+
+/**
  * idr_replace - replace pointer for given id
  * @idp: idr handle
  * @ptr: pointer you want associated with the id
@@ -542,15 +634,18 @@ EXPORT_SYMBOL(idr_for_each);
  * A -ENOENT return indicates that @id was not found.
  * A -EINVAL return indicates that @id was not within valid constraints.
  *
- * The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
+ * The caller must serialize with writers.
  */
 void *idr_replace(struct idr *idp, void *ptr, int id)
 {
 	int n;
 	struct idr_layer *p, *old_p;
 
-	n = idp->layers * IDR_BITS;
 	p = idp->top;
+	if (!p)
+		return ERR_PTR(-EINVAL);
+
+	n = (p->layer+1) * IDR_BITS;
 
 	id &= MAX_ID_MASK;
 
@@ -568,22 +663,16 @@ void *idr_replace(struct idr *idp, void *ptr, int id)
 		return ERR_PTR(-ENOENT);
 
 	old_p = p->ary[n];
-	p->ary[n] = ptr;
+	rcu_assign_pointer(p->ary[n], ptr);
 
 	return old_p;
 }
 EXPORT_SYMBOL(idr_replace);
 
-static void idr_cache_ctor(struct kmem_cache *idr_layer_cache, void *idr_layer)
-{
-	memset(idr_layer, 0, sizeof(struct idr_layer));
-}
-
 void __init idr_init_cache(void)
 {
 	idr_layer_cache = kmem_cache_create("idr_layer_cache",
-				sizeof(struct idr_layer), 0, SLAB_PANIC,
-				idr_cache_ctor);
+				sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
 }
 
 /**
@@ -674,7 +763,7 @@ EXPORT_SYMBOL(ida_pre_get);
  * and go back to the ida_pre_get() call.  If the ida is full, it will
  * return -ENOSPC.
  *
- * @p_id returns a value in the range 0 ... 0x7fffffff.
+ * @p_id returns a value in the range @starting_id ... 0x7fffffff.
  */
 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
 {
@@ -710,7 +799,8 @@ int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
 			return -EAGAIN;
 
 		memset(bitmap, 0, sizeof(struct ida_bitmap));
-		pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap;
+		rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
+				(void *)bitmap);
 		pa[0]->count++;
 	}