lib/sort: Add priv pointer to swap function

Adding support to have priv pointer in swap callback function.

Following the initial change on cmp callback functions [1]
and adding SWAP_WRAPPER macro to identify sort call of sort_r.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-2-jolsa@kernel.org

[1] 4333fb96ca ("media: lib/sort.c: implement sort() variant taking context argument")

include/linux/sort.h

@@ -6,7 +6,7 @@
 
 void sort_r(void *base, size_t num, size_t size,
 	    cmp_r_func_t cmp_func,
-	    swap_func_t swap_func,
+	    swap_r_func_t swap_func,
 	    const void *priv);
 
 void sort(void *base, size_t num, size_t size,

include/linux/types.h

@@ -226,6 +226,7 @@ struct callback_head {
 typedef void (*rcu_callback_t)(struct rcu_head *head);
 typedef void (*call_rcu_func_t)(struct rcu_head *head, rcu_callback_t func);
 
+typedef void (*swap_r_func_t)(void *a, void *b, int size, const void *priv);
 typedef void (*swap_func_t)(void *a, void *b, int size);
 
 typedef int (*cmp_r_func_t)(const void *a, const void *b, const void *priv);

lib/sort.c

@@ -122,16 +122,27 @@ static void swap_bytes(void *a, void *b, size_t n)
  * a pointer, but small integers make for the smallest compare
  * instructions.
  */
-#define SWAP_WORDS_64 (swap_func_t)0
+#define SWAP_WORDS_64 (swap_r_func_t)0
-#define SWAP_WORDS_32 (swap_func_t)1
+#define SWAP_WORDS_32 (swap_r_func_t)1
-#define SWAP_BYTES    (swap_func_t)2
+#define SWAP_BYTES    (swap_r_func_t)2
+#define SWAP_WRAPPER  (swap_r_func_t)3
+
+struct wrapper {
+	cmp_func_t cmp;
+	swap_func_t swap;
+};
 
 /*
  * The function pointer is last to make tail calls most efficient if the
  * compiler decides not to inline this function.
  */
-static void do_swap(void *a, void *b, size_t size, swap_func_t swap_func)
+static void do_swap(void *a, void *b, size_t size, swap_r_func_t swap_func, const void *priv)
 {
+	if (swap_func == SWAP_WRAPPER) {
+		((const struct wrapper *)priv)->swap(a, b, (int)size);
+		return;
+	}
+
 	if (swap_func == SWAP_WORDS_64)
 		swap_words_64(a, b, size);
 	else if (swap_func == SWAP_WORDS_32)
@@ -139,7 +150,7 @@ static void do_swap(void *a, void *b, size_t size, swap_func_t swap_func)
 	else if (swap_func == SWAP_BYTES)
 		swap_bytes(a, b, size);
 	else
-		swap_func(a, b, (int)size);
+		swap_func(a, b, (int)size, priv);
 }
 
 #define _CMP_WRAPPER ((cmp_r_func_t)0L)
@@ -147,7 +158,7 @@ static void do_swap(void *a, void *b, size_t size, swap_func_t swap_func)
 static int do_cmp(const void *a, const void *b, cmp_r_func_t cmp, const void *priv)
 {
 	if (cmp == _CMP_WRAPPER)
-		return ((cmp_func_t)(priv))(a, b);
+		return ((const struct wrapper *)priv)->cmp(a, b);
 	return cmp(a, b, priv);
 }
 
@@ -198,7 +209,7 @@ static size_t parent(size_t i, unsigned int lsbit, size_t size)
  */
 void sort_r(void *base, size_t num, size_t size,
 	    cmp_r_func_t cmp_func,
-	    swap_func_t swap_func,
+	    swap_r_func_t swap_func,
 	    const void *priv)
 {
 	/* pre-scale counters for performance */
@@ -208,6 +219,10 @@ void sort_r(void *base, size_t num, size_t size,
 	if (!a)		/* num < 2 || size == 0 */
 		return;
 
+	/* called from 'sort' without swap function, let's pick the default */
+	if (swap_func == SWAP_WRAPPER && !((struct wrapper *)priv)->swap)
+		swap_func = NULL;
+
 	if (!swap_func) {
 		if (is_aligned(base, size, 8))
 			swap_func = SWAP_WORDS_64;
@@ -230,7 +245,7 @@ void sort_r(void *base, size_t num, size_t size,
 		if (a)			/* Building heap: sift down --a */
 			a -= size;
 		else if (n -= size)	/* Sorting: Extract root to --n */
-			do_swap(base, base + n, size, swap_func);
+			do_swap(base, base + n, size, swap_func, priv);
 		else			/* Sort complete */
 			break;
 
@@ -257,7 +272,7 @@ void sort_r(void *base, size_t num, size_t size,
 		c = b;			/* Where "a" belongs */
 		while (b != a) {	/* Shift it into place */
 			b = parent(b, lsbit, size);
-			do_swap(base + b, base + c, size, swap_func);
+			do_swap(base + b, base + c, size, swap_func, priv);
 		}
 	}
 }
@@ -267,6 +282,11 @@ void sort(void *base, size_t num, size_t size,
 	  cmp_func_t cmp_func,
 	  swap_func_t swap_func)
 {
-	return sort_r(base, num, size, _CMP_WRAPPER, swap_func, cmp_func);
+	struct wrapper w = {
+		.cmp  = cmp_func,
+		.swap = swap_func,
+	};
+
+	return sort_r(base, num, size, _CMP_WRAPPER, SWAP_WRAPPER, &w);
 }
 EXPORT_SYMBOL(sort);