1 files changed, 364 insertions, 0 deletions
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
new file mode 100644
index 000000000..cd8e13d41
--- /dev/null
+++ b/mm/page_reporting.c
@@ -0,0 +1,364 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/page_reporting.h>
+#include <linux/gfp.h>
+#include <linux/export.h>
+#include <linux/delay.h>
+#include <linux/scatterlist.h>
+
+#include "page_reporting.h"
+#include "internal.h"
+
+#define PAGE_REPORTING_DELAY	(2 * HZ)
+static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
+
+enum {
+	PAGE_REPORTING_IDLE = 0,
+	PAGE_REPORTING_REQUESTED,
+	PAGE_REPORTING_ACTIVE
+};
+
+/* request page reporting */
+static void
+__page_reporting_request(struct page_reporting_dev_info *prdev)
+{
+	unsigned int state;
+
+	/* Check to see if we are in desired state */
+	state = atomic_read(&prdev->state);
+	if (state == PAGE_REPORTING_REQUESTED)
+		return;
+
+	/*
+	 *  If reporting is already active there is nothing we need to do.
+	 *  Test against 0 as that represents PAGE_REPORTING_IDLE.
+	 */
+	state = atomic_xchg(&prdev->state, PAGE_REPORTING_REQUESTED);
+	if (state != PAGE_REPORTING_IDLE)
+		return;
+
+	/*
+	 * Delay the start of work to allow a sizable queue to build. For
+	 * now we are limiting this to running no more than once every
+	 * couple of seconds.
+	 */
+	schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
+}
+
+/* notify prdev of free page reporting request */
+void __page_reporting_notify(void)
+{
+	struct page_reporting_dev_info *prdev;
+
+	/*
+	 * We use RCU to protect the pr_dev_info pointer. In almost all
+	 * cases this should be present, however in the unlikely case of
+	 * a shutdown this will be NULL and we should exit.
+	 */
+	rcu_read_lock();
+	prdev = rcu_dereference(pr_dev_info);
+	if (likely(prdev))
+		__page_reporting_request(prdev);
+
+	rcu_read_unlock();
+}
+
+static void
+page_reporting_drain(struct page_reporting_dev_info *prdev,
+		     struct scatterlist *sgl, unsigned int nents, bool reported)
+{
+	struct scatterlist *sg = sgl;
+
+	/*
+	 * Drain the now reported pages back into their respective
+	 * free lists/areas. We assume at least one page is populated.
+	 */
+	do {
+		struct page *page = sg_page(sg);
+		int mt = get_pageblock_migratetype(page);
+		unsigned int order = get_order(sg->length);
+
+		__putback_isolated_page(page, order, mt);
+
+		/* If the pages were not reported due to error skip flagging */
+		if (!reported)
+			continue;
+
+		/*
+		 * If page was not comingled with another page we can
+		 * consider the result to be "reported" since the page
+		 * hasn't been modified, otherwise we will need to
+		 * report on the new larger page when we make our way
+		 * up to that higher order.
+		 */
+		if (PageBuddy(page) && buddy_order(page) == order)
+			__SetPageReported(page);
+	} while ((sg = sg_next(sg)));
+
+	/* reinitialize scatterlist now that it is empty */
+	sg_init_table(sgl, nents);
+}
+
+/*
+ * The page reporting cycle consists of 4 stages, fill, report, drain, and
+ * idle. We will cycle through the first 3 stages until we cannot obtain a
+ * full scatterlist of pages, in that case we will switch to idle.
+ */
+static int
+page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
+		     unsigned int order, unsigned int mt,
+		     struct scatterlist *sgl, unsigned int *offset)
+{
+	struct free_area *area = &zone->free_area[order];
+	struct list_head *list = &area->free_list[mt];
+	unsigned int page_len = PAGE_SIZE << order;
+	struct page *page, *next;
+	long budget;
+	int err = 0;
+
+	/*
+	 * Perform early check, if free area is empty there is
+	 * nothing to process so we can skip this free_list.
+	 */
+	if (list_empty(list))
+		return err;
+
+	spin_lock_irq(&zone->lock);
+
+	/*
+	 * Limit how many calls we will be making to the page reporting
+	 * device for this list. By doing this we avoid processing any
+	 * given list for too long.
+	 *
+	 * The current value used allows us enough calls to process over a
+	 * sixteenth of the current list plus one additional call to handle
+	 * any pages that may have already been present from the previous
+	 * list processed. This should result in us reporting all pages on
+	 * an idle system in about 30 seconds.
+	 *
+	 * The division here should be cheap since PAGE_REPORTING_CAPACITY
+	 * should always be a power of 2.
+	 */
+	budget = DIV_ROUND_UP(area->nr_free, PAGE_REPORTING_CAPACITY * 16);
+
+	/* loop through free list adding unreported pages to sg list */
+	list_for_each_entry_safe(page, next, list, lru) {
+		/* We are going to skip over the reported pages. */
+		if (PageReported(page))
+			continue;
+
+		/*
+		 * If we fully consumed our budget then update our
+		 * state to indicate that we are requesting additional
+		 * processing and exit this list.
+		 */
+		if (budget < 0) {
+			atomic_set(&prdev->state, PAGE_REPORTING_REQUESTED);
+			next = page;
+			break;
+		}
+
+		/* Attempt to pull page from list and place in scatterlist */
+		if (*offset) {
+			if (!__isolate_free_page(page, order)) {
+				next = page;
+				break;
+			}
+
+			/* Add page to scatter list */
+			--(*offset);
+			sg_set_page(&sgl[*offset], page, page_len, 0);
+
+			continue;
+		}
+
+		/*
+		 * Make the first non-reported page in the free list
+		 * the new head of the free list before we release the
+		 * zone lock.
+		 */
+		if (!list_is_first(&page->lru, list))
+			list_rotate_to_front(&page->lru, list);
+
+		/* release lock before waiting on report processing */
+		spin_unlock_irq(&zone->lock);
+
+		/* begin processing pages in local list */
+		err = prdev->report(prdev, sgl, PAGE_REPORTING_CAPACITY);
+
+		/* reset offset since the full list was reported */
+		*offset = PAGE_REPORTING_CAPACITY;
+
+		/* update budget to reflect call to report function */
+		budget--;
+
+		/* reacquire zone lock and resume processing */
+		spin_lock_irq(&zone->lock);
+
+		/* flush reported pages from the sg list */
+		page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, !err);
+
+		/*
+		 * Reset next to first entry, the old next isn't valid
+		 * since we dropped the lock to report the pages
+		 */
+		next = list_first_entry(list, struct page, lru);
+
+		/* exit on error */
+		if (err)
+			break;
+	}
+
+	/* Rotate any leftover pages to the head of the freelist */
+	if (&next->lru != list && !list_is_first(&next->lru, list))
+		list_rotate_to_front(&next->lru, list);
+
+	spin_unlock_irq(&zone->lock);
+
+	return err;
+}
+
+static int
+page_reporting_process_zone(struct page_reporting_dev_info *prdev,
+			    struct scatterlist *sgl, struct zone *zone)
+{
+	unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY;
+	unsigned long watermark;
+	int err = 0;
+
+	/* Generate minimum watermark to be able to guarantee progress */
+	watermark = low_wmark_pages(zone) +
+		    (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER);
+
+	/*
+	 * Cancel request if insufficient free memory or if we failed
+	 * to allocate page reporting statistics for the zone.
+	 */
+	if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
+		return err;
+
+	/* Process each free list starting from lowest order/mt */
+	for (order = PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) {
+		for (mt = 0; mt < MIGRATE_TYPES; mt++) {
+			/* We do not pull pages from the isolate free list */
+			if (is_migrate_isolate(mt))
+				continue;
+
+			err = page_reporting_cycle(prdev, zone, order, mt,
+						   sgl, &offset);
+			if (err)
+				return err;
+		}
+	}
+
+	/* report the leftover pages before going idle */
+	leftover = PAGE_REPORTING_CAPACITY - offset;
+	if (leftover) {
+		sgl = &sgl[offset];
+		err = prdev->report(prdev, sgl, leftover);
+
+		/* flush any remaining pages out from the last report */
+		spin_lock_irq(&zone->lock);
+		page_reporting_drain(prdev, sgl, leftover, !err);
+		spin_unlock_irq(&zone->lock);
+	}
+
+	return err;
+}
+
+static void page_reporting_process(struct work_struct *work)
+{
+	struct delayed_work *d_work = to_delayed_work(work);
+	struct page_reporting_dev_info *prdev =
+		container_of(d_work, struct page_reporting_dev_info, work);
+	int err = 0, state = PAGE_REPORTING_ACTIVE;
+	struct scatterlist *sgl;
+	struct zone *zone;
+
+	/*
+	 * Change the state to "Active" so that we can track if there is
+	 * anyone requests page reporting after we complete our pass. If
+	 * the state is not altered by the end of the pass we will switch
+	 * to idle and quit scheduling reporting runs.
+	 */
+	atomic_set(&prdev->state, state);
+
+	/* allocate scatterlist to store pages being reported on */
+	sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, sizeof(*sgl), GFP_KERNEL);
+	if (!sgl)
+		goto err_out;
+
+	sg_init_table(sgl, PAGE_REPORTING_CAPACITY);
+
+	for_each_zone(zone) {
+		err = page_reporting_process_zone(prdev, sgl, zone);
+		if (err)
+			break;
+	}
+
+	kfree(sgl);
+err_out:
+	/*
+	 * If the state has reverted back to requested then there may be
+	 * additional pages to be processed. We will defer for 2s to allow
+	 * more pages to accumulate.
+	 */
+	state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE);
+	if (state == PAGE_REPORTING_REQUESTED)
+		schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
+}
+
+static DEFINE_MUTEX(page_reporting_mutex);
+DEFINE_STATIC_KEY_FALSE(page_reporting_enabled);
+
+int page_reporting_register(struct page_reporting_dev_info *prdev)
+{
+	int err = 0;
+
+	mutex_lock(&page_reporting_mutex);
+
+	/* nothing to do if already in use */
+	if (rcu_access_pointer(pr_dev_info)) {
+		err = -EBUSY;
+		goto err_out;
+	}
+
+	/* initialize state and work structures */
+	atomic_set(&prdev->state, PAGE_REPORTING_IDLE);
+	INIT_DELAYED_WORK(&prdev->work, &page_reporting_process);
+
+	/* Begin initial flush of zones */
+	__page_reporting_request(prdev);
+
+	/* Assign device to allow notifications */
+	rcu_assign_pointer(pr_dev_info, prdev);
+
+	/* enable page reporting notification */
+	if (!static_key_enabled(&page_reporting_enabled)) {
+		static_branch_enable(&page_reporting_enabled);
+		pr_info("Free page reporting enabled\n");
+	}
+err_out:
+	mutex_unlock(&page_reporting_mutex);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(page_reporting_register);
+
+void page_reporting_unregister(struct page_reporting_dev_info *prdev)
+{
+	mutex_lock(&page_reporting_mutex);
+
+	if (rcu_access_pointer(pr_dev_info) == prdev) {
+		/* Disable page reporting notification */
+		RCU_INIT_POINTER(pr_dev_info, NULL);
+		synchronize_rcu();
+
+		/* Flush any existing work, and lock it out */
+		cancel_delayed_work_sync(&prdev->work);
+	}
+
+	mutex_unlock(&page_reporting_mutex);
+}
+EXPORT_SYMBOL_GPL(page_reporting_unregister);