mm/damon/paddr: use a separate function for 'DAMOS_PAGEOUT' handling

This commit moves code for 'DAMOS_PAGEOUT' handling of the physical
address space monitoring operations set to a separate function so that its
caller, 'damon_pa_apply_scheme()', can be more easily extended for
additional DAMOS actions later.

Link: https://lkml.kernel.org/r/20220613192301.8817-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/paddr.c

@@ -204,16 +204,11 @@ static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)
 	return max_nr_accesses;
 }
 
-static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
-		struct damon_target *t, struct damon_region *r,
-		struct damos *scheme)
+static unsigned long damon_pa_pageout(struct damon_region *r)
 {
 	unsigned long addr, applied;
 	LIST_HEAD(page_list);
 
-	if (scheme->action != DAMOS_PAGEOUT)
-		return 0;
-
 	for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) {
 		struct page *page = damon_get_page(PHYS_PFN(addr));
 
@@ -238,6 +233,19 @@ static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
 	return applied * PAGE_SIZE;
 }
 
+static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
+		struct damon_target *t, struct damon_region *r,
+		struct damos *scheme)
+{
+	switch (scheme->action) {
+	case DAMOS_PAGEOUT:
+		return damon_pa_pageout(r);
+	default:
+		break;
+	}
+	return 0;
+}
+
 static int damon_pa_scheme_score(struct damon_ctx *context,
 		struct damon_target *t, struct damon_region *r,
 		struct damos *scheme)