linux-kernel - [PATCH v3 09/17] lib min_heap: Add min_heap_sift

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Message-Id: <20240406164727.577914-10-visitorckw@gmail.com>
Date: Sun,  7 Apr 2024 00:47:19 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: colyli@...e.de,
	kent.overstreet@...ux.dev,
	msakai@...hat.com,
	peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	akpm@...ux-foundation.org
Cc: bfoster@...hat.com,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	jserv@...s.ncku.edu.tw,
	linux-bcache@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-bcachefs@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Kuan-Wei Chiu <visitorckw@...il.com>
Subject: [PATCH v3 09/17] lib min_heap: Add min_heap_sift_up()

Add min_heap_sift_up() to sift up the element at index 'idx' in the
heap.

Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
---
 include/linux/min_heap.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/min_heap.h b/include/linux/min_heap.h
index 9391f7cc9da9..201f59cb3558 100644
--- a/include/linux/min_heap.h
+++ b/include/linux/min_heap.h
@@ -111,6 +111,26 @@ void __min_heapify(min_heap_char *heap, int pos, size_t elem_size,
 #define min_heapify(_heap, _pos, _func, _args)	\
 	__min_heapify((min_heap_char *)_heap, _pos, __minheap_obj_size(_heap), _func, _args)
 
+/* Sift up ith element from the heap, O(log2(nr)). */
+static __always_inline
+void __min_heap_sift_up(min_heap_char *heap, size_t elem_size, size_t idx,
+		const struct min_heap_callbacks *func, void *args)
+{
+	void *data = heap->data;
+	size_t parent;
+
+	while (idx) {
+		parent = (idx - 1) / 2;
+		if (func->less(data + parent * elem_size, data + idx * elem_size, args))
+			break;
+		func->swp(data + parent * elem_size, data + idx * elem_size, args);
+		idx = parent;
+	}
+}
+
+#define min_heap_sift_up(_heap, _idx, _func, _args)	\
+	__min_heap_sift_up((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, _func, _args)
+
 /* Floyd's approach to heapification that is O(nr). */
 static __always_inline
 void __min_heapify_all(min_heap_char *heap, size_t elem_size,
-- 
2.34.1