scoutfs: bring back sort_priv

Bring back sort_priv, we have need for sorting with a caller argument.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile

@@ -33,6 +33,7 @@ scoutfs-y +=			\
 	quorum.o		\
 	scoutfs_trace.o		\
 	server.o		\
+	sort_priv.o		\
 	spbm.o			\
 	srch.o			\
 	super.o			\

kmod/src/sort_priv.c

@@ -0,0 +1,71 @@
+/*
+ * A copy of sort() from upstream with a priv argument that's passed
+ * to comparison, like list_sort().
+ */
+
+/* ------------------------ */
+
+/*
+ * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
+ *
+ * Jan 23 2005  Matt Mackall <mpm@selenic.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sort.h>
+#include <linux/slab.h>
+#include "sort_priv.h"
+
+/**
+ * sort - sort an array of elements
+ * @priv: caller's pointer to pass to comparison and swap functions
+ * @base: pointer to data to sort
+ * @num: number of elements
+ * @size: size of each element
+ * @cmp_func: pointer to comparison function
+ * @swap_func: pointer to swap function or NULL
+ *
+ * This function does a heapsort on the given array. You may provide a
+ * swap_func function optimized to your element type.
+ *
+ * Sorting time is O(n log n) both on average and worst-case. While
+ * qsort is about 20% faster on average, it suffers from exploitable
+ * O(n*n) worst-case behavior and extra memory requirements that make
+ * it less suitable for kernel use.
+ */
+
+void sort_priv(void *priv, void *base, size_t num, size_t size,
+	       int (*cmp_func)(void *priv, const void *, const void *),
+	       void (*swap_func)(void *priv, void *, void *, int size))
+{
+	/* pre-scale counters for performance */
+	int i = (num/2 - 1) * size, n = num * size, c, r;
+
+	/* heapify */
+	for ( ; i >= 0; i -= size) {
+		for (r = i; r * 2 + size < n; r  = c) {
+			c = r * 2 + size;
+			if (c < n - size &&
+			    cmp_func(priv, base + c, base + c + size) < 0)
+				c += size;
+			if (cmp_func(priv, base + r, base + c) >= 0)
+				break;
+			swap_func(priv, base + r, base + c, size);
+		}
+	}
+
+	/* sort */
+	for (i = n - size; i > 0; i -= size) {
+		swap_func(priv, base, base + i, size);
+		for (r = 0; r * 2 + size < i; r = c) {
+			c = r * 2 + size;
+			if (c < i - size &&
+			    cmp_func(priv, base + c, base + c + size) < 0)
+				c += size;
+			if (cmp_func(priv, base + r, base + c) >= 0)
+				break;
+			swap_func(priv, base + r, base + c, size);
+		}
+	}
+}

kmod/src/sort_priv.h

@@ -0,0 +1,8 @@
+#ifndef _SCOUTFS_SORT_PRIV_H_
+#define _SCOUTFS_SORT_PRIV_H_
+
+void sort_priv(void *priv, void *base, size_t num, size_t size,
+	       int (*cmp_func)(void *priv, const void *, const void *),
+	       void (*swap_func)(void *priv, void *, void *, int size));
+
+#endif