scsi: sbitmap: Add helpers for updating allocation hint

Add helpers for updating allocation hint so that we can avoid duplicate
code.

Prepare for moving allocation hint into sbitmap.

Link: https://lore.kernel.org/r/20210122023317.687987-4-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

lib/sbitmap.c

@@ -9,6 +9,55 @@
 #include <linux/sbitmap.h>
 #include <linux/seq_file.h>
 
+static int init_alloc_hint(struct sbitmap_queue *sbq, gfp_t flags)
+{
+	unsigned depth = sbq->sb.depth;
+
+	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
+	if (!sbq->alloc_hint)
+		return -ENOMEM;
+
+	if (depth && !sbq->sb.round_robin) {
+		int i;
+
+		for_each_possible_cpu(i)
+			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
+	}
+
+	return 0;
+}
+
+static inline unsigned update_alloc_hint_before_get(struct sbitmap_queue *sbq,
+						    unsigned int depth)
+{
+	unsigned hint;
+
+	hint = this_cpu_read(*sbq->alloc_hint);
+	if (unlikely(hint >= depth)) {
+		hint = depth ? prandom_u32() % depth : 0;
+		this_cpu_write(*sbq->alloc_hint, hint);
+	}
+
+	return hint;
+}
+
+static inline void update_alloc_hint_after_get(struct sbitmap_queue *sbq,
+					       unsigned int depth,
+					       unsigned int hint,
+					       unsigned int nr)
+{
+	if (nr == -1) {
+		/* If the map is full, a hint won't do us much good. */
+		this_cpu_write(*sbq->alloc_hint, 0);
+	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
+		/* Only update the hint if we used it. */
+		hint = nr + 1;
+		if (hint >= depth - 1)
+			hint = 0;
+		this_cpu_write(*sbq->alloc_hint, hint);
+	}
+}
+
 /*
  * See if we have deferred clears that we can batch move
  */
@@ -355,17 +404,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 	if (ret)
 		return ret;
 
-	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
-	if (!sbq->alloc_hint) {
+	if (init_alloc_hint(sbq, flags) != 0) {
 		sbitmap_free(&sbq->sb);
 		return -ENOMEM;
 	}
 
-	if (depth && !round_robin) {
-		for_each_possible_cpu(i)
-			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
-	}
-
 	sbq->min_shallow_depth = UINT_MAX;
 	sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 	atomic_set(&sbq->wake_index, 0);
@@ -418,24 +461,10 @@ int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 	unsigned int hint, depth;
 	int nr;
 
-	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
-	if (unlikely(hint >= depth)) {
-		hint = depth ? prandom_u32() % depth : 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	hint = update_alloc_hint_before_get(sbq, depth);
 	nr = sbitmap_get(&sbq->sb, hint);
-
-	if (nr == -1) {
-		/* If the map is full, a hint won't do us much good. */
-		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
-		/* Only update the hint if we used it. */
-		hint = nr + 1;
-		if (hint >= depth - 1)
-			hint = 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	update_alloc_hint_after_get(sbq, depth, hint, nr);
 
 	return nr;
 }
@@ -449,24 +478,10 @@ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 
 	WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 
-	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
-	if (unlikely(hint >= depth)) {
-		hint = depth ? prandom_u32() % depth : 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	hint = update_alloc_hint_before_get(sbq, depth);
 	nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
-
-	if (nr == -1) {
-		/* If the map is full, a hint won't do us much good. */
-		this_cpu_write(*sbq->alloc_hint, 0);
-	} else if (nr == hint || unlikely(sbq->sb.round_robin)) {
-		/* Only update the hint if we used it. */
-		hint = nr + 1;
-		if (hint >= depth - 1)
-			hint = 0;
-		this_cpu_write(*sbq->alloc_hint, hint);
-	}
+	update_alloc_hint_after_get(sbq, depth, hint, nr);
 
 	return nr;
 }