RE: [PATCH 1/2] Drivers: hv: hv_balloon: report offline pages as being used

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Thursday, February 19, 2015 8:27 AM
> To: KY Srinivasan; devel@xxxxxxxxxxxxxxxxxxxxxx
> Cc: Haiyang Zhang; linux-kernel@xxxxxxxxxxxxxxx; Dexuan Cui
> Subject: [PATCH 1/2] Drivers: hv: hv_balloon: report offline pages as being
> used
> 
> When hot-added memory pages are not brought online or when some
> memory blocks
> are sent offline the subsequent ballooning process kills the guest with OOM
> killer. This happens as we don't report these pages as neither used nor free
> and apparently host algorythm considers them as being unused. Keep track
> of
> all online/offline operations and report all currently offline pages as being
> used so host won't try to balloon them out.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
>  drivers/hv/hv_balloon.c | 33 ++++++++++++++++++++++++---------
>  1 file changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index a095b70..e4b4454 100644
> --- a/drivers/hv/hv_balloon.c
> +++ b/drivers/hv/hv_balloon.c
> @@ -503,6 +503,8 @@ struct hv_dynmem_device {
>  	 * Number of pages we have currently ballooned out.
>  	 */
>  	unsigned int num_pages_ballooned;
> +	unsigned int num_pages_onlined;
> +	unsigned int num_pages_added;
> 
>  	/*
>  	 * State to manage the ballooning (up) operation.
> @@ -556,12 +558,15 @@ static void post_status(struct hv_dynmem_device
> *dm);
>  static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
>  			      void *v)
>  {
> +	struct memory_notify *mem = (struct memory_notify *)v;
> +
>  	switch (val) {
>  	case MEM_GOING_ONLINE:
>  		mutex_lock(&dm_device.ha_region_mutex);
>  		break;
> 
>  	case MEM_ONLINE:
> +		dm_device.num_pages_onlined += mem->nr_pages;
>  	case MEM_CANCEL_ONLINE:

Why are we not adjusting num_pages_onlined when we cancel the online
Operation.

K. Y
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