mm/damon/vaddr: support DAMON-based Operation Schemes

This makes DAMON's default primitives for virtual address spaces to
support DAMON-based Operation Schemes (DAMOS) by implementing actions
application functions and registering it to the monitoring context.  The
implementation simply links 'madvise()' for related DAMOS actions.  That
is, 'madvise(MADV_WILLNEED)' is called for 'WILLNEED' DAMOS action and
similar for other actions ('COLD', 'PAGEOUT', 'HUGEPAGE', 'NOHUGEPAGE').

So, the kernel space DAMON users can now use the DAMON-based
optimizations with only small amount of code.

Link: https://lkml.kernel.org/r/20211001125604.29660-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rienjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: sjp38

include/linux/damon.h

@@ -337,6 +337,8 @@ void damon_va_prepare_access_checks(struct damon_ctx *ctx);
 unsigned int damon_va_check_accesses(struct damon_ctx *ctx);
 bool damon_va_target_valid(void *t);
 void damon_va_cleanup(struct damon_ctx *ctx);
+int damon_va_apply_scheme(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme);
 void damon_va_set_primitives(struct damon_ctx *ctx);
 
 #endif	/* CONFIG_DAMON_VADDR */

mm/damon/vaddr.c

@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "damon-va: " fmt
 
+#include <asm-generic/mman-common.h>
 #include <linux/damon.h>
 #include <linux/hugetlb.h>
 #include <linux/mm.h>
@@ -658,6 +659,60 @@ bool damon_va_target_valid(void *target)
 	return false;
 }
 
+#ifndef CONFIG_ADVISE_SYSCALLS
+static int damos_madvise(struct damon_target *target, struct damon_region *r,
+			int behavior)
+{
+	return -EINVAL;
+}
+#else
+static int damos_madvise(struct damon_target *target, struct damon_region *r,
+			int behavior)
+{
+	struct mm_struct *mm;
+	int ret = -ENOMEM;
+
+	mm = damon_get_mm(target);
+	if (!mm)
+		goto out;
+
+	ret = do_madvise(mm, PAGE_ALIGN(r->ar.start),
+			PAGE_ALIGN(r->ar.end - r->ar.start), behavior);
+	mmput(mm);
+out:
+	return ret;
+}
+#endif	/* CONFIG_ADVISE_SYSCALLS */
+
+int damon_va_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme)
+{
+	int madv_action;
+
+	switch (scheme->action) {
+	case DAMOS_WILLNEED:
+		madv_action = MADV_WILLNEED;
+		break;
+	case DAMOS_COLD:
+		madv_action = MADV_COLD;
+		break;
+	case DAMOS_PAGEOUT:
+		madv_action = MADV_PAGEOUT;
+		break;
+	case DAMOS_HUGEPAGE:
+		madv_action = MADV_HUGEPAGE;
+		break;
+	case DAMOS_NOHUGEPAGE:
+		madv_action = MADV_NOHUGEPAGE;
+		break;
+	default:
+		pr_warn("Wrong action %d\n", scheme->action);
+		return -EINVAL;
+	}
+
+	return damos_madvise(t, r, madv_action);
+}
+
 void damon_va_set_primitives(struct damon_ctx *ctx)
 {
 	ctx->primitive.init = damon_va_init;
@@ -667,6 +722,7 @@ void damon_va_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.reset_aggregated = NULL;
 	ctx->primitive.target_valid = damon_va_target_valid;
 	ctx->primitive.cleanup = NULL;
+	ctx->primitive.apply_scheme = damon_va_apply_scheme;
 }
 
 #include "vaddr-test.h"