Implement a DAMON core API for reporting page fault events to DAMON.  It
is a wrapper of damon_report_access().

This is a temporal hack.  In future versions that will have no RFC tag,
only damon_report_access() may be used.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 10 ++++++++++
 mm/damon/core.c       | 17 +++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index b9359c76a6f1..b8ebb2aa02c8 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -1017,6 +1017,13 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control);
 int damos_walk(struct damon_ctx *ctx, struct damos_walk_control *control);
 
 void damon_report_access(struct damon_access_report *report);
+#ifdef CONFIG_MMU
+void damon_report_page_fault(struct vm_fault *vmf, bool huge_pmd);
+#else
+static inline void damon_report_page_fault(struct vm_fault *vmf, bool huge_pmd)
+{
+}
+#endif
 
 int damon_set_region_biggest_system_ram_default(struct damon_target *t,
 				unsigned long *start, unsigned long *end,
@@ -1027,6 +1034,9 @@ int damon_set_region_biggest_system_ram_default(struct damon_target *t,
 static inline void damon_report_access(struct damon_access_report *report)
 {
 }
+static inline void damon_report_page_fault(struct vm_fault *vmf, bool huge_pmd)
+{
+}
 
 #endif	/* CONFIG_DAMON */
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 89305d42e116..296117d5e7f7 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1579,6 +1579,23 @@ void damon_report_access(struct damon_access_report *report)
 	mutex_unlock(&damon_access_reports_lock);
 }
 
+#ifdef CONFIG_MMU
+void damon_report_page_fault(struct vm_fault *vmf, bool huge_pmd)
+{
+	struct damon_access_report access_report = {
+		.size = 1,	/* todo: set appripriately */
+	};
+
+	if (huge_pmd)
+		access_report.addr = PFN_PHYS(pmd_pfn(vmf->orig_pmd));
+	else
+		access_report.addr = PFN_PHYS(pte_pfn(vmf->orig_pte));
+	/* todo: report vmf->address as virtual address */
+
+	damon_report_access(&access_report);
+}
+#endif
+
 /*
  * Warn and fix corrupted ->nr_accesses[_bp] for investigations and preventing
  * the problem being propagated.
-- 
2.47.3