aboutsummaryrefslogtreecommitdiffstats
path: root/lib/idr.c
diff options
context:
space:
mode:
authorTejun Heo <htejun@gmail.com>2007-06-14 03:45:13 +0900
committerGreg Kroah-Hartman <gregkh@suse.de>2007-07-11 16:09:03 -0700
commit72dba584b695d8bc8c1a50ed54ad4cba7c62314d (patch)
treeb0938ea773953f869b22101bb021e5710d0a0fec /lib/idr.c
parente33ac8bdb0c84fe7afd2c45537b763faf28c589e (diff)
downloadmrst-s0i3-test-72dba584b695d8bc8c1a50ed54ad4cba7c62314d.tar.gz
mrst-s0i3-test-72dba584b695d8bc8c1a50ed54ad4cba7c62314d.tar.xz
mrst-s0i3-test-72dba584b695d8bc8c1a50ed54ad4cba7c62314d.zip
ida: implement idr based id allocator
Implement idr based id allocator. ida is used the same way idr is used but lacks id -> ptr translation and thus consumes much less memory. struct ida_bitmap is attached as leaf nodes to idr tree which is managed by the idr code. Each ida_bitmap is 128bytes long and contains slightly less than a thousand slots. ida is more aggressive with releasing extra resources acquired using ida_pre_get(). After every successful id allocation, ida frees one reserved idr_layer if possible. Reserved ida_bitmap is not freed automatically but only one ida_bitmap is reserved and it's almost always used right away. Under most circumstances, ida won't hold on to memory for too long which isn't actively used. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'lib/idr.c')
-rw-r--r--lib/idr.c245
1 files changed, 245 insertions, 0 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 30b33e2e7a5..b98f01a2eb9 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -506,3 +506,248 @@ void idr_init(struct idr *idp)
spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
+
+
+/*
+ * IDA - IDR based ID allocator
+ *
+ * this is id allocator without id -> pointer translation. Memory
+ * usage is much lower than full blown idr because each id only
+ * occupies a bit. ida uses a custom leaf node which contains
+ * IDA_BITMAP_BITS slots.
+ *
+ * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
+ */
+
+static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
+{
+ unsigned long flags;
+
+ if (!ida->free_bitmap) {
+ spin_lock_irqsave(&ida->idr.lock, flags);
+ if (!ida->free_bitmap) {
+ ida->free_bitmap = bitmap;
+ bitmap = NULL;
+ }
+ spin_unlock_irqrestore(&ida->idr.lock, flags);
+ }
+
+ kfree(bitmap);
+}
+
+/**
+ * ida_pre_get - reserve resources for ida allocation
+ * @ida: ida handle
+ * @gfp_mask: memory allocation flag
+ *
+ * This function should be called prior to locking and calling the
+ * following function. It preallocates enough memory to satisfy the
+ * worst possible allocation.
+ *
+ * If the system is REALLY out of memory this function returns 0,
+ * otherwise 1.
+ */
+int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
+{
+ /* allocate idr_layers */
+ if (!idr_pre_get(&ida->idr, gfp_mask))
+ return 0;
+
+ /* allocate free_bitmap */
+ if (!ida->free_bitmap) {
+ struct ida_bitmap *bitmap;
+
+ bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
+ if (!bitmap)
+ return 0;
+
+ free_bitmap(ida, bitmap);
+ }
+
+ return 1;
+}
+EXPORT_SYMBOL(ida_pre_get);
+
+/**
+ * ida_get_new_above - allocate new ID above or equal to a start id
+ * @ida: ida handle
+ * @staring_id: id to start search at
+ * @p_id: pointer to the allocated handle
+ *
+ * Allocate new ID above or equal to @ida. It should be called with
+ * any required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * 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.
+ */
+int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
+{
+ struct idr_layer *pa[MAX_LEVEL];
+ struct ida_bitmap *bitmap;
+ unsigned long flags;
+ int idr_id = starting_id / IDA_BITMAP_BITS;
+ int offset = starting_id % IDA_BITMAP_BITS;
+ int t, id;
+
+ restart:
+ /* get vacant slot */
+ t = idr_get_empty_slot(&ida->idr, idr_id, pa);
+ if (t < 0) {
+ if (t == -1)
+ return -EAGAIN;
+ else /* will be -3 */
+ return -ENOSPC;
+ }
+
+ if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
+ return -ENOSPC;
+
+ if (t != idr_id)
+ offset = 0;
+ idr_id = t;
+
+ /* if bitmap isn't there, create a new one */
+ bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
+ if (!bitmap) {
+ spin_lock_irqsave(&ida->idr.lock, flags);
+ bitmap = ida->free_bitmap;
+ ida->free_bitmap = NULL;
+ spin_unlock_irqrestore(&ida->idr.lock, flags);
+
+ if (!bitmap)
+ return -EAGAIN;
+
+ memset(bitmap, 0, sizeof(struct ida_bitmap));
+ pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap;
+ pa[0]->count++;
+ }
+
+ /* lookup for empty slot */
+ t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
+ if (t == IDA_BITMAP_BITS) {
+ /* no empty slot after offset, continue to the next chunk */
+ idr_id++;
+ offset = 0;
+ goto restart;
+ }
+
+ id = idr_id * IDA_BITMAP_BITS + t;
+ if (id >= MAX_ID_BIT)
+ return -ENOSPC;
+
+ __set_bit(t, bitmap->bitmap);
+ if (++bitmap->nr_busy == IDA_BITMAP_BITS)
+ idr_mark_full(pa, idr_id);
+
+ *p_id = id;
+
+ /* Each leaf node can handle nearly a thousand slots and the
+ * whole idea of ida is to have small memory foot print.
+ * Throw away extra resources one by one after each successful
+ * allocation.
+ */
+ if (ida->idr.id_free_cnt || ida->free_bitmap) {
+ struct idr_layer *p = alloc_layer(&ida->idr);
+ if (p)
+ kmem_cache_free(idr_layer_cache, p);
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(ida_get_new_above);
+
+/**
+ * ida_get_new - allocate new ID
+ * @ida: idr handle
+ * @p_id: pointer to the allocated handle
+ *
+ * Allocate new ID. It should be called with any required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * 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.
+ */
+int ida_get_new(struct ida *ida, int *p_id)
+{
+ return ida_get_new_above(ida, 0, p_id);
+}
+EXPORT_SYMBOL(ida_get_new);
+
+/**
+ * ida_remove - remove the given ID
+ * @ida: ida handle
+ * @id: ID to free
+ */
+void ida_remove(struct ida *ida, int id)
+{
+ struct idr_layer *p = ida->idr.top;
+ int shift = (ida->idr.layers - 1) * IDR_BITS;
+ int idr_id = id / IDA_BITMAP_BITS;
+ int offset = id % IDA_BITMAP_BITS;
+ int n;
+ struct ida_bitmap *bitmap;
+
+ /* clear full bits while looking up the leaf idr_layer */
+ while ((shift > 0) && p) {
+ n = (idr_id >> shift) & IDR_MASK;
+ __clear_bit(n, &p->bitmap);
+ p = p->ary[n];
+ shift -= IDR_BITS;
+ }
+
+ if (p == NULL)
+ goto err;
+
+ n = idr_id & IDR_MASK;
+ __clear_bit(n, &p->bitmap);
+
+ bitmap = (void *)p->ary[n];
+ if (!test_bit(offset, bitmap->bitmap))
+ goto err;
+
+ /* update bitmap and remove it if empty */
+ __clear_bit(offset, bitmap->bitmap);
+ if (--bitmap->nr_busy == 0) {
+ __set_bit(n, &p->bitmap); /* to please idr_remove() */
+ idr_remove(&ida->idr, idr_id);
+ free_bitmap(ida, bitmap);
+ }
+
+ return;
+
+ err:
+ printk(KERN_WARNING
+ "ida_remove called for id=%d which is not allocated.\n", id);
+}
+EXPORT_SYMBOL(ida_remove);
+
+/**
+ * ida_destroy - release all cached layers within an ida tree
+ * ida: ida handle
+ */
+void ida_destroy(struct ida *ida)
+{
+ idr_destroy(&ida->idr);
+ kfree(ida->free_bitmap);
+}
+EXPORT_SYMBOL(ida_destroy);
+
+/**
+ * ida_init - initialize ida handle
+ * @ida: ida handle
+ *
+ * This function is use to set up the handle (@ida) that you will pass
+ * to the rest of the functions.
+ */
+void ida_init(struct ida *ida)
+{
+ memset(ida, 0, sizeof(struct ida));
+ idr_init(&ida->idr);
+
+}
+EXPORT_SYMBOL(ida_init);