1 files changed, 69 insertions, 2 deletions

diff --git a/lib/idr.c b/lib/idr.c
index 7ecdfdb5309e..e2adc457abb4 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -100,7 +100,7 @@ EXPORT_SYMBOL_GPL(idr_alloc);
  * @end: The maximum ID (exclusive).
  * @gfp: Memory allocation flags.
  *
- * Allocates an unused ID in the range specified by @nextid and @end.  If
+ * Allocates an unused ID in the range specified by @start and @end.  If
  * @end is <= 0, it is treated as one larger than %INT_MAX.  This allows
  * callers to use @start + N as @end as long as N is within integer range.
  * The search for an unused ID will start at the last ID allocated and will
@@ -477,6 +477,73 @@ nospc:
 EXPORT_SYMBOL(ida_alloc_range);
 
 /**
+ * ida_find_first_range - Get the lowest used ID.
+ * @ida: IDA handle.
+ * @min: Lowest ID to get.
+ * @max: Highest ID to get.
+ *
+ * Get the lowest used ID between @min and @max, inclusive.  The returned
+ * ID will not exceed %INT_MAX, even if @max is larger.
+ *
+ * Context: Any context. Takes and releases the xa_lock.
+ * Return: The lowest used ID, or errno if no used ID is found.
+ */
+int ida_find_first_range(struct ida *ida, unsigned int min, unsigned int max)
+{
+	unsigned long index = min / IDA_BITMAP_BITS;
+	unsigned int offset = min % IDA_BITMAP_BITS;
+	unsigned long *addr, size, bit;
+	unsigned long tmp = 0;
+	unsigned long flags;
+	void *entry;
+	int ret;
+
+	if ((int)min < 0)
+		return -EINVAL;
+	if ((int)max < 0)
+		max = INT_MAX;
+
+	xa_lock_irqsave(&ida->xa, flags);
+
+	entry = xa_find(&ida->xa, &index, max / IDA_BITMAP_BITS, XA_PRESENT);
+	if (!entry) {
+		ret = -ENOENT;
+		goto err_unlock;
+	}
+
+	if (index > min / IDA_BITMAP_BITS)
+		offset = 0;
+	if (index * IDA_BITMAP_BITS + offset > max) {
+		ret = -ENOENT;
+		goto err_unlock;
+	}
+
+	if (xa_is_value(entry)) {
+		tmp = xa_to_value(entry);
+		addr = &tmp;
+		size = BITS_PER_XA_VALUE;
+	} else {
+		addr = ((struct ida_bitmap *)entry)->bitmap;
+		size = IDA_BITMAP_BITS;
+	}
+
+	bit = find_next_bit(addr, size, offset);
+
+	xa_unlock_irqrestore(&ida->xa, flags);
+
+	if (bit == size ||
+	    index * IDA_BITMAP_BITS + bit > max)
+		return -ENOENT;
+
+	return index * IDA_BITMAP_BITS + bit;
+
+err_unlock:
+	xa_unlock_irqrestore(&ida->xa, flags);
+	return ret;
+}
+EXPORT_SYMBOL(ida_find_first_range);
+
+/**
  * ida_free() - Release an allocated ID.
  * @ida: IDA handle.
  * @id: Previously allocated ID.
@@ -508,7 +575,7 @@ void ida_free(struct ida *ida, unsigned int id)
 			goto delete;
 		xas_store(&xas, xa_mk_value(v));
 	} else {
-		if (!test_bit(bit, bitmap->bitmap))
+		if (!bitmap || !test_bit(bit, bitmap->bitmap))
 			goto err;
 		__clear_bit(bit, bitmap->bitmap);
 		xas_set_mark(&xas, XA_FREE_MARK);