aufs: kmalloc/kfree wrappers

Very basic, simple and stupid wrappers for kmalloc family.
It tries kfree_ruc() as possible, with hoping a better performance.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+-include ${srctree}/${src}/priv_def.mk
+
+# sparse requires the full pathname
+ccflags-y += -include ${srctree}/include/uapi/linux/aufs_type.h
+
+obj-$(CONFIG_AUFS_FS) += aufs.o
+aufs-y := module.o

fs/aufs/aufs.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * all header files
+ */
+
+#ifndef __AUFS_H__
+#define __AUFS_H__
+
+#ifdef __KERNEL__
+
+#include "module.h"
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_H__ */

fs/aufs/debug.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * debug print functions
+ */
+
+#ifndef __AUFS_DEBUG_H__
+#define __AUFS_DEBUG_H__
+
+#ifdef __KERNEL__
+
+#ifdef CONFIG_AUFS_DEBUG
+#define AuDebugOn(a)		BUG_ON(a)
+#else
+#define AuDebugOn(a)		do {} while (0)
+#endif /* CONFIG_AUFS_DEBUG */
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DEBUG_H__ */

fs/aufs/module.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * module global variables and operations
+ */
+
+#include <linux/module.h>
+#include "aufs.h"
+
+/* shrinkable realloc */
+void *au_krealloc(void *p, unsigned int new_sz, gfp_t gfp, int may_shrink)
+{
+	size_t sz;
+	int diff;
+
+	sz = 0;
+	diff = -1;
+	if (p) {
+#if 0 /* unused */
+		if (!new_sz) {
+			au_kfree_rcu(p);
+			p = NULL;
+			goto out;
+		}
+#else
+		AuDebugOn(!new_sz);
+#endif
+		sz = ksize(p);
+		diff = au_kmidx_sub(sz, new_sz);
+	}
+	if (sz && !diff)
+		goto out;
+
+	if (sz < new_sz)
+		/* expand or SLOB */
+		p = krealloc(p, new_sz, gfp);
+	else if (new_sz < sz && may_shrink) {
+		/* shrink */
+		void *q;
+
+		q = kmalloc(new_sz, gfp);
+		if (q) {
+			if (p) {
+				memcpy(q, p, new_sz);
+				au_kfree_try_rcu(p);
+			}
+			p = q;
+		} else
+			p = NULL;
+	}
+
+out:
+	return p;
+}
+
+void *au_kzrealloc(void *p, unsigned int nused, unsigned int new_sz, gfp_t gfp,
+		   int may_shrink)
+{
+	p = au_krealloc(p, new_sz, gfp, may_shrink);
+	if (p && new_sz > nused)
+		memset(p + nused, 0, new_sz - nused);
+	return p;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * functions for module interface.
+ */
+MODULE_LICENSE("GPL");
+/* MODULE_LICENSE("GPL v2"); */
+MODULE_AUTHOR("Junjiro R. Okajima <aufs-users@lists.sourceforge.net>");
+MODULE_DESCRIPTION(AUFS_NAME
+	" -- Advanced multi layered unification filesystem");
+MODULE_VERSION(AUFS_VERSION);
+
+/* ---------------------------------------------------------------------- */
+
+static int __init aufs_init(void)
+{
+	/* since we define pr_fmt, call printk directly */
+	printk(KERN_INFO AUFS_NAME " " AUFS_VERSION "\n");
+
+	return 0;
+}
+
+module_init(aufs_init);

fs/aufs/module.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * module initialization and module-global
+ */
+
+#ifndef __AUFS_MODULE_H__
+#define __AUFS_MODULE_H__
+
+#ifdef __KERNEL__
+
+#include <linux/slab.h>
+#include "debug.h"
+
+void *au_krealloc(void *p, unsigned int new_sz, gfp_t gfp, int may_shrink);
+void *au_kzrealloc(void *p, unsigned int nused, unsigned int new_sz, gfp_t gfp,
+		   int may_shrink);
+
+/*
+ * Comparing the size of the object with sizeof(struct rcu_head)
+ * case 1: object is always larger
+ *	--> au_kfree_rcu() or au_kfree_do_rcu()
+ * case 2: object is always smaller
+ *	--> au_kfree_small()
+ * case 3: object can be any size
+ *	--> au_kfree_try_rcu()
+ */
+
+static inline void au_kfree_do_rcu(const void *p)
+{
+	struct {
+		struct rcu_head rcu;
+	} *a = (void *)p;
+
+	kfree_rcu(a, rcu);
+}
+
+#define au_kfree_rcu(_p) do {						\
+		typeof(_p) p = (_p);					\
+		BUILD_BUG_ON(sizeof(*p) < sizeof(struct rcu_head));	\
+		if (p)							\
+			au_kfree_do_rcu(p);				\
+	} while (0)
+
+#define au_kfree_do_sz_test(sz)	(sz >= sizeof(struct rcu_head))
+#define au_kfree_sz_test(p)	(p && au_kfree_do_sz_test(ksize(p)))
+
+static inline void au_kfree_try_rcu(const void *p)
+{
+	if (!p)
+		return;
+	if (au_kfree_sz_test(p))
+		au_kfree_do_rcu(p);
+	else
+		kfree(p);
+}
+
+static inline void au_kfree_small(const void *p)
+{
+	if (!p)
+		return;
+	AuDebugOn(au_kfree_sz_test(p));
+	kfree(p);
+}
+
+static inline int au_kmidx_sub(size_t sz, size_t new_sz)
+{
+#ifndef CONFIG_SLOB
+	return kmalloc_index(sz) - kmalloc_index(new_sz);
+#else
+	return -1; /* SLOB is untested */
+#endif
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_MODULE_H__ */