linux-kernel - [RFC PATCH 1/3] ksmall_array: introduce kernel small arrays

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Date:   Tue, 19 Sep 2017 12:31:39 +0400
From:   Ilya Matveychikov <matvejchikov@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/3] ksmall_array: introduce kernel small arrays

Signed-off-by: Ilya V. Matveychikov <matvejchikov@...il.com>
---
 include/linux/small_array.h | 35 +++++++++++++++++++++++++++++++++++
 lib/Makefile                |  2 +-
 lib/cmdline.c               |  4 +++-
 lib/ksmall_array.c          | 26 ++++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/small_array.h
 create mode 100644 lib/ksmall_array.c

diff --git a/include/linux/small_array.h b/include/linux/small_array.h
new file mode 100644
index 0000000..c5ccbe4d
--- /dev/null
+++ b/include/linux/small_array.h
@@ -0,0 +1,35 @@
+#ifndef __SMALL_ARRAY_H__
+#define __SMALL_ARRAY_H__
+
+/*
+ * Kingdom of Small Arrays (KSA)
+ */
+
+#include <linux/build_bug.h>
+
+#define KSA_S_BITS		8
+#define KSA_N_BITS		12
+
+struct ksmall_array {
+	unsigned int s : KSA_S_BITS;	/* sizeof(item) */
+	unsigned int n : KSA_N_BITS;	/* number of items stored */
+	unsigned int m : KSA_N_BITS;	/* maximum number of items allowed */
+	unsigned char v[0];
+};
+
+#define KSA_DECLARE(name, type, count)				\
+	struct {						\
+		struct ksmall_array ksa;			\
+		type data[count];				\
+	} name = {{ .s = sizeof(type), .n = 0, .m = count }}
+
+#define KSA(p)			((struct ksmall_array *)(p))
+#define KSA_S(p)		KSA(p)->s
+#define KSA_N(p)		KSA(p)->n
+#define KSA_M(p)		KSA(p)->m
+#define KSA_V(p, t)		((t *)KSA(p)->v)
+#define KSA_GET(p, i, v)	((i < KSA_N(p)) ? (p)->data[i] : v)
+
+extern char *ksa_parse_ints(const char *str, struct ksmall_array *ksa);
+
+#endif /* __SMALL_ARRAY_H__ */
diff --git a/lib/Makefile b/lib/Makefile
index 40c1837..502f4b4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -30,7 +30,7 @@ lib-$(CONFIG_SMP) += cpumask.o
 lib-$(CONFIG_DMA_NOOP_OPS) += dma-noop.o
 lib-$(CONFIG_DMA_VIRT_OPS) += dma-virt.o

-lib-y	+= kobject.o klist.o
+lib-y	+= kobject.o klist.o ksmall_array.o
 obj-y	+= lockref.o

 obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
diff --git a/lib/cmdline.c b/lib/cmdline.c
index 4c0888c..233c4eb 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -63,8 +63,10 @@ int get_option(char **str, int *pint)
 		(*str)++;
 		return 2;
 	}
-	if (**str == '-')
+	if (**str == '-') {
+		(*str)++;
 		return 3;
+	}

 	return 1;
 }
diff --git a/lib/ksmall_array.c b/lib/ksmall_array.c
new file mode 100644
index 0000000..ecc8403
--- /dev/null
+++ b/lib/ksmall_array.c
@@ -0,0 +1,26 @@
+#include <linux/small_array.h>
+#include <linux/bug.h>
+
+char *ksa_parse_ints(const char *str, struct ksmall_array *ksa)
+{
+	int res, a, b;
+
+	BUG_ON(ksa->s != sizeof(int));
+
+	while (ksa->n < ksa->m) {
+		res = get_option((char **)&str, &a); b = a;
+		if (res == 0) break;
+		if (res == 3) res = get_option((char **)&str, &b);
+		if (res == 0) break;
+		while (a <= b && (ksa->n < ksa->m))
+			KSA_V(ksa, int)[ksa->n++] = a++;
+	}
+
+	return (char *)str;
+}
+EXPORT_SYMBOL(ksa_parse_ints);
+
+static void __attribute__((unused)) ksa_build_check(void)
+{
+	BUILD_BUG_ON(sizeof(struct ksmall_array) != sizeof(unsigned int));
+}
--
2.7.4