hv_balloon: don't check for memhp_auto_online manually (bc58ebd5) · Commits · 戴 / test

We get the MEM_ONLINE notifier call if memory is added right from the kernel via add_memory() or later from user space. Let's get rid of the "ha_waiting" flag - the wait event has an inbuilt mechanism (->done) for that. Initialize the wait event only once and reinitialize before adding memory. Unconditionally call complete() and wait_for_completion_timeout(). If there are no waiters, complete() will only increment ->done - which will be reset by reinit_completion(). If complete() has already been called, wait_for_completion_timeout() will not wait. There is still the chance for a small race between concurrent reinit_completion() and complete(). If complete() wins, we would not wait - which is tolerable (and the race exists in current code as well). Note: We only wait for "some" memory to get onlined, which seems to be good enough for now. [akpm@linux-foundation.org: register_memory_notifier() after init_completion(), per David] Signed-off-by:

David Hildenbrand <david@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Reviewed-by:

Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by:

Baoquan He <bhe@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Eduardo Habkost <ehabkost@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Yumei Huang <yuhuang@redhat.com> Link: http://lkml.kernel.org/r/20200317104942.11178-6-david@redhat.com Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/hv/hv_balloon.c

+10 −15

Original line number	Diff line number	Diff line
		@@ -533,7 +533,6 @@ struct hv_dynmem_device {
		* State to synchronize hot-add.
		*/
		struct completion ol_waitevent;
		bool ha_waiting;
		/*
		* This thread handles hot-add
		* requests from the host as well as notifying
		@@ -634,10 +633,7 @@ static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
		switch (val) {
		case MEM_ONLINE:
		case MEM_CANCEL_ONLINE:
		if (dm_device.ha_waiting) {
		dm_device.ha_waiting = false;
		complete(&dm_device.ol_waitevent);
		}
		break;

		case MEM_OFFLINE:
		@@ -726,8 +722,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
		has->covered_end_pfn += processed_pfn;
		spin_unlock_irqrestore(&dm_device.ha_lock, flags);

		init_completion(&dm_device.ol_waitevent);
		dm_device.ha_waiting = !memhp_auto_online;
		reinit_completion(&dm_device.ol_waitevent);

		nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
		ret = add_memory(nid, PFN_PHYS((start_pfn)),
		@@ -753,15 +748,14 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
		}

		/*
		* Wait for the memory block to be onlined when memory onlining
		* is done outside of kernel (memhp_auto_online). Since the hot
		* add has succeeded, it is ok to proceed even if the pages in
		* the hot added region have not been "onlined" within the
		* allowed time.
		* Wait for memory to get onlined. If the kernel onlined the
		* memory when adding it, this will return directly. Otherwise,
		* it will wait for user space to online the memory. This helps
		* to avoid adding memory faster than it is getting onlined. As
		* adding succeeded, it is ok to proceed even if the memory was
		* not onlined in time.
		*/
		if (dm_device.ha_waiting)
		wait_for_completion_timeout(&dm_device.ol_waitevent,
		5*HZ);
		wait_for_completion_timeout(&dm_device.ol_waitevent, 5 * HZ);
		post_status(&dm_device);
		}
		}
		@@ -1706,6 +1700,7 @@ static int balloon_probe(struct hv_device *dev,

		#ifdef CONFIG_MEMORY_HOTPLUG
		set_online_page_callback(&hv_online_page);
		init_completion(&dm_device.ol_waitevent);
		register_memory_notifier(&hv_memory_nb);
		#endif

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