sbitmap: add helper to clear a batch of tags

sbitmap currently only supports clearing tags one-by-one, add a helper
that allows the caller to pass in an array of tags to clear.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/sbitmap.h

@@ -528,6 +528,17 @@ void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 			 unsigned int cpu);
 
+/**
+ * sbitmap_queue_clear_batch() - Free a batch of allocated bits
+ * &struct sbitmap_queue.
+ * @sbq: Bitmap to free from.
+ * @offset: offset for each tag in array
+ * @tags: array of tags
+ * @nr_tags: number of tags in array
+ */
+void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
+				int *tags, int nr_tags);
+
 static inline int sbq_index_inc(int index)
 {
 	return (index + 1) & (SBQ_WAIT_QUEUES - 1);

lib/sbitmap.c

@@ -628,6 +628,46 @@ void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 
+static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag)
+{
+	if (likely(!sb->round_robin && tag < sb->depth))
+		*per_cpu_ptr(sb->alloc_hint, cpu) = tag;
+}
+
+void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
+				int *tags, int nr_tags)
+{
+	struct sbitmap *sb = &sbq->sb;
+	unsigned long *addr = NULL;
+	unsigned long mask = 0;
+	int i;
+
+	smp_mb__before_atomic();
+	for (i = 0; i < nr_tags; i++) {
+		const int tag = tags[i] - offset;
+		unsigned long *this_addr;
+
+		/* since we're clearing a batch, skip the deferred map */
+		this_addr = &sb->map[SB_NR_TO_INDEX(sb, tag)].word;
+		if (!addr) {
+			addr = this_addr;
+		} else if (addr != this_addr) {
+			atomic_long_andnot(mask, (atomic_long_t *) addr);
+			mask = 0;
+			addr = this_addr;
+		}
+		mask |= (1UL << SB_NR_TO_BIT(sb, tag));
+	}
+
+	if (mask)
+		atomic_long_andnot(mask, (atomic_long_t *) addr);
+
+	smp_mb__after_atomic();
+	sbitmap_queue_wake_up(sbq);
+	sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(),
+					tags[nr_tags - 1] - offset);
+}
+
 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 			 unsigned int cpu)
 {
@@ -652,9 +692,7 @@ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 	 */
 	smp_mb__after_atomic();
 	sbitmap_queue_wake_up(sbq);
-
-	if (likely(!sbq->sb.round_robin && nr < sbq->sb.depth))
-		*per_cpu_ptr(sbq->sb.alloc_hint, cpu) = nr;
+	sbitmap_update_cpu_hint(&sbq->sb, cpu, nr);
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);