[RFC PATCH 01/13] mm/damon/paddr: Support the pageout scheme

[sj38 . park]

From: SeongJae Park <sjpark@xxxxxxxxx>

This commit makes the DAMON primitives for physical address space to
support the pageout action for DAMON-based Operation Schemes.  IOW, now
the users can implement their own data access-aware reclamations for
whole system using DAMOS.

Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx>
---
 mm/damon/paddr.c        | 38 +++++++++++++++++++++++++++++++++++++-
 mm/damon/prmtv-common.c |  2 +-
 mm/damon/prmtv-common.h |  2 ++
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index b92b07a3ce53..303db372e53b 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -7,6 +7,9 @@
 
 #define pr_fmt(fmt) "damon-pa: " fmt
 
+#include <linux/swap.h>
+
+#include "../internal.h"
 #include "prmtv-common.h"
 
 /*
@@ -85,6 +88,39 @@ bool damon_pa_target_valid(void *t)
 	return true;
 }
 
+int damon_pa_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme)
+{
+	unsigned long addr;
+	LIST_HEAD(page_list);
+
+	if (scheme->action != DAMOS_PAGEOUT)
+		return -EINVAL;
+
+	for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) {
+		struct page *page = damon_get_page(PHYS_PFN(addr));
+
+		if (!page)
+			continue;
+
+		ClearPageReferenced(page);
+		test_and_clear_page_young(page);
+		if (isolate_lru_page(page)) {
+			put_page(page);
+			continue;
+		}
+		if (PageUnevictable(page)) {
+			putback_lru_page(page);
+		} else {
+			list_add(&page->lru, &page_list);
+			put_page(page);
+		}
+	}
+	reclaim_pages(&page_list);
+	cond_resched();
+	return 0;
+}
+
 void damon_pa_set_primitives(struct damon_ctx *ctx)
 {
 	ctx->primitive.init = NULL;
@@ -94,5 +130,5 @@ void damon_pa_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.reset_aggregated = NULL;
 	ctx->primitive.target_valid = damon_pa_target_valid;
 	ctx->primitive.cleanup = NULL;
-	ctx->primitive.apply_scheme = NULL;
+	ctx->primitive.apply_scheme = damon_pa_apply_scheme;
 }
diff --git a/mm/damon/prmtv-common.c b/mm/damon/prmtv-common.c
index 08e9318d67ed..01c1c1b37859 100644
--- a/mm/damon/prmtv-common.c
+++ b/mm/damon/prmtv-common.c
@@ -14,7 +14,7 @@
  * The body of this function is stolen from the 'page_idle_get_page()'.  We
  * steal rather than reuse it because the code is quite simple.
  */
-static struct page *damon_get_page(unsigned long pfn)
+struct page *damon_get_page(unsigned long pfn)
 {
 	struct page *page = pfn_to_online_page(pfn);
 
diff --git a/mm/damon/prmtv-common.h b/mm/damon/prmtv-common.h
index 939c41af6b59..ba0c4eecbb79 100644
--- a/mm/damon/prmtv-common.h
+++ b/mm/damon/prmtv-common.h
@@ -18,6 +18,8 @@
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32_max(r - l))
 
+struct page *damon_get_page(unsigned long pfn);
+
 void damon_va_mkold(struct mm_struct *mm, unsigned long addr);
 bool damon_va_young(struct mm_struct *mm, unsigned long addr,
 			unsigned long *page_sz);
-- 
2.17.1