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From: Kuan-Wei Chiu <visitorckw@gmail.com>
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	Kuan-Wei Chiu <visitorckw@gmail.com>
Subject: [PATCH v4 10/16] lib min_heap: Add min_heap_del()
Date: Thu, 25 Apr 2024 22:18:20 +0800
Message-Id: <20240425141826.840077-11-visitorckw@gmail.com>
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Add min_heap_del() to delete the element at index 'idx' in the heap.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reviewed-by: Ian Rogers <irogers@google.com>
---
Changes in v4:
- Replace memcpy() with func->swp() in heap_del() due to issues with
  set_backpointer in bcachefs when setting idx.

 include/linux/min_heap.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/linux/min_heap.h b/include/linux/min_heap.h
index 201f59cb3558..c94f9d303205 100644
--- a/include/linux/min_heap.h
+++ b/include/linux/min_heap.h
@@ -212,4 +212,28 @@ void __min_heap_push(min_heap_char *heap, const void *element, size_t elem_size,
 #define min_heap_push(_heap, _element, _func, _args)	\
 	__min_heap_push((min_heap_char *)_heap, _element, __minheap_obj_size(_heap), _func, _args)
 
+/* Remove ith element from the heap, O(log2(nr)). */
+static __always_inline
+bool __min_heap_del(min_heap_char *heap, size_t elem_size, size_t idx,
+		const struct min_heap_callbacks *func, void *args)
+{
+	void *data = heap->data;
+
+	if (WARN_ONCE(heap->nr <= 0, "Popping an empty heap"))
+		return false;
+
+	/* Place last element at the root (position 0) and then sift down. */
+	heap->nr--;
+	if (idx == heap->nr)
+		return true;
+	func->swp(data + (idx * elem_size), data + (heap->nr * elem_size), args);
+	__min_heap_sift_up(heap, elem_size, idx, func, args);
+	__min_heapify(heap, idx, elem_size, func, args);
+
+	return true;
+}
+
+#define min_heap_del(_heap, _idx, _func, _args)	\
+	__min_heap_del((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, _func, _args)
+
 #endif /* _LINUX_MIN_HEAP_H */
-- 
2.34.1