The patch titled
Subject: hv_balloon: don't check for memhp_auto_online manually
has been added to the -mm tree. Its filename is
hv_balloon-dont-check-for-memhp_auto_online-manually.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/hv_balloon-dont-check-for-memhp_auto_online-manually.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/hv_balloon-dont-check-for-memhp_auto_online-manually.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-hyperv@xxxxxxxxxxxxxxx, David Hildenbrand <david@xxxxxxxxxx>, "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, Wei Liu <wei.liu@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxxxx>, Oscar Salvador <osalvador@xxxxxxx>, "Rafael J. Wysocki" <rafael@xxxxxxxxxx>, Baoquan He <bhe@xxxxxxxxxx>, Wei Yang <richard.weiyang@xxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Subject: [PATCH v2 5/8] hv_balloon: don't check for memhp_auto_online manually
Date: Tue, 17 Mar 2020 11:49:39 +0100
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.
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: linux-hyperv@xxxxxxxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
drivers/hv/hv_balloon.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index a02ce43d778d..af5e09f08130 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -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);
- }
+ 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);
}
}
@@ -1707,6 +1701,7 @@ static int balloon_probe(struct hv_device *dev,
#ifdef CONFIG_MEMORY_HOTPLUG
set_online_page_callback(&hv_online_page);
register_memory_notifier(&hv_memory_nb);
+ init_completion(&dm_device.ol_waitevent);
#endif
hv_set_drvdata(dev, &dm_device);
--
2.24.1
Patches currently in -mm which might be from david@xxxxxxxxxx are
drivers-base-memoryc-cache-memory-blocks-in-xarray-to-accelerate-lookup-fix.patch
virtio-balloon-switch-back-to-oom-handler-for-virtio_balloon_f_deflate_on_oom.patch
drivers-base-memoryc-indicate-all-memory-blocks-as-removable.patch
drivers-base-memoryc-drop-section_count.patch
drivers-base-memoryc-drop-pages_correctly_probed.patch
mm-page_extc-drop-pfn_present-check-when-onlining.patch
mm-memory_hotplug-simplify-calculation-of-number-of-pages-in-__remove_pages.patch
mm-memory_hotplug-cleanup-__add_pages.patch
drivers-base-memory-rename-mmop_online_keep-to-mmop_online.patch
drivers-base-memory-map-mmop_offline-to-0.patch
drivers-base-memory-store-mapping-between-mmop_-and-string-in-an-array.patch
powernv-memtrace-always-online-added-memory-blocks.patch
hv_balloon-dont-check-for-memhp_auto_online-manually.patch
mm-memory_hotplug-unexport-memhp_auto_online.patch
mm-memory_hotplug-convert-memhp_auto_online-to-store-an-online_type.patch
mm-memory_hotplug-allow-to-specify-a-default-online_type.patch
