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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/drivers/xen/xenbus/xenbus_probe_backend.c
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@@ -45,9 +45,9 @@
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 #include <linux/mm.h>
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 #include <linux/notifier.h>
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 #include <linux/export.h>
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+#include <linux/semaphore.h>
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 #include <asm/page.h>
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-#include <asm/pgtable.h>
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 #include <asm/xen/hypervisor.h>
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 #include <asm/hypervisor.h>
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 #include <xen/xenbus.h>
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@@ -205,7 +205,6 @@
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 		.uevent		= xenbus_uevent_backend,
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 		.probe		= xenbus_dev_probe,
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 		.remove		= xenbus_dev_remove,
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-		.shutdown	= xenbus_dev_shutdown,
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 		.dev_groups	= xenbus_dev_groups,
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 	},
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 };
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@@ -255,6 +254,41 @@
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 	return NOTIFY_DONE;
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 }
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+static int backend_reclaim_memory(struct device *dev, void *data)
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+{
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+	const struct xenbus_driver *drv;
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+	struct xenbus_device *xdev;
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+
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+	if (!dev->driver)
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+		return 0;
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+	drv = to_xenbus_driver(dev->driver);
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+	if (drv && drv->reclaim_memory) {
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+		xdev = to_xenbus_device(dev);
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+		if (down_trylock(&xdev->reclaim_sem))
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+			return 0;
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+		drv->reclaim_memory(xdev);
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+		up(&xdev->reclaim_sem);
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+	}
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+	return 0;
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+}
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+
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+/*
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+ * Returns 0 always because we are using shrinker to only detect memory
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+ * pressure.
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+ */
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+static unsigned long backend_shrink_memory_count(struct shrinker *shrinker,
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+				struct shrink_control *sc)
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+{
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+	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL,
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+			backend_reclaim_memory);
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+	return 0;
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+}
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+
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+static struct shrinker backend_memory_shrinker = {
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+	.count_objects = backend_shrink_memory_count,
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+	.seeks = DEFAULT_SEEKS,
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+};
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+
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 static int __init xenbus_probe_backend_init(void)
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 {
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 	static struct notifier_block xenstore_notifier = {
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@@ -271,6 +305,9 @@
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 	register_xenstore_notifier(&xenstore_notifier);
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+	if (register_shrinker(&backend_memory_shrinker))
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+		pr_warn("shrinker registration failed\n");
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+
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 	return 0;
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 }
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 subsys_initcall(xenbus_probe_backend_init);