[PATCH RFC v2 16/18] mm: page_reporting: add flush parameter with page budget

Michael S. Tsirkin
2026-04-20T12:51:14Z

Add a write-only module parameter "flush" that triggers immediate
page reporting. The value specifies approximately how many pages
(at page_reporting_order) to report. The flush loops through
reporting cycles until the budget is exhausted, all pages are
reported, or a signal is pending.

echo 512 > /sys/module/page_reporting/parameters/flush

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Assisted-by: cursor-agent:GPT-5.4-xhigh
---
mm/page_reporting.c | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)

diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index 5e1e1a924b0c..3560f272ab70 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -354,6 +354,48 @@ static void page_reporting_process(struct work_struct *work)
static DEFINE_MUTEX(page_reporting_mutex);
DEFINE_STATIC_KEY_FALSE(page_reporting_enabled);

+static int page_reporting_flush_set(const char *val,
+ const struct kernel_param *kp)
+{
+ struct page_reporting_dev_info *prdev;
+ unsigned int budget;
+ int err;
+
+ err = kstrtouint(val, 0, &budget);
+ if (err)
+ return err;
+ if (!budget)
+ return 0;
+
+ mutex_lock(&page_reporting_mutex);
+ prdev = rcu_dereference_protected(pr_dev_info,
+ lockdep_is_held(&page_reporting_mutex));
+ if (prdev) {
+ unsigned int reported;
+
+ for (reported = 0; reported < budget;
+ reported += PAGE_REPORTING_CAPACITY) {
+ flush_delayed_work(&prdev->work);
+ __page_reporting_request(prdev);
+ flush_delayed_work(&prdev->work);
+ if (atomic_read(&prdev->state) == PAGE_REPORTING_IDLE)
+ break;
+ if (signal_pending(current))
+ break;
+ }
+ }
+ mutex_unlock(&page_reporting_mutex);
+ return 0;
+}
+
+static const struct kernel_param_ops flush_ops = {
+ .set = page_reporting_flush_set,
+ .get = param_get_uint,
+};
+static unsigned int page_reporting_flush;
+module_param_cb(flush, &flush_ops, &page_reporting_flush, 0200);
+MODULE_PARM_DESC(flush, "Report up to N pages at page_reporting_order");
+
int page_reporting_register(struct page_reporting_dev_info *prdev)
{
int err = 0;
--
MST