[RFC PATCH 3/6] mm/damon/vaddr: implement sz_filter_passed for migrate_{hot,cold} action

[SJ Park <sj@kernel.org>]

Support of DAMOS ops filter and sz_filter_passed support is up to each
operation set.  DAMON_VADDR supports both for only damos_stat action.
It intentionally does not support those for madvise-based actions
because applying filters could make it unnecessarily complicated and
expensive.  The vaddr implementation of migrate_{hot,cold} action does
support DAMOS ops filters but sz_filter_passed.  There is no real reason
to not support sz_filter_passed.  Add the support.

Pass the sz_filter_passed pointer to the filter applying logic and
accumulate the number.

Closes: https://sashiko.dev/#/bug/linux-986e8b64-8e65-4e32-970f-4d3ebdf8206e
Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/vaddr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index c271b6d63c027..112095c2d53fd 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -776,6 +776,7 @@ static bool damos_va_filter_out(struct damos *scheme, struct folio *folio,
 struct damos_va_migrate_private {
 	struct list_head *migration_lists;
 	struct damos *scheme;
+	unsigned long *sz_filter_passed;
 };
 
 /*
@@ -840,6 +841,7 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr,
 	struct damos_va_migrate_private *priv = walk->private;
 	struct list_head *migration_lists = priv->migration_lists;
 	struct damos *s = priv->scheme;
+	unsigned long *sz_filter_passed = priv->sz_filter_passed;
 	struct damos_migrate_dests *dests = &s->migrate_dests;
 	struct folio *folio;
 	spinlock_t *ptl;
@@ -858,6 +860,7 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr,
 			goto huge_out;
 		if (damos_va_filter_out(s, folio, walk->vma, addr, NULL, pmd))
 			goto huge_out;
+		*sz_filter_passed += folio_size(folio);
 		damos_va_migrate_dests_add(folio, walk->vma, addr, dests,
 				migration_lists);
 huge_out:
@@ -885,6 +888,7 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr,
 		nr = folio_nr_pages(folio) - page_idx;
 		if (damos_va_filter_out(s, folio, walk->vma, addr, pte, NULL))
 			continue;
+		*sz_filter_passed += folio_size(folio);
 		damos_va_migrate_dests_add(folio, walk->vma, addr, dests,
 				migration_lists);
 	}
-- 
2.47.3