Drivers: hv: hv_balloon: refuse to balloon below the floor

When host asks us to balloon up we need to be sure we're not committing suicide
by overballooning. Use already existent 'floor' metric as our lowest possible
value for free ram.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 53932b3e197396900aed3eb9999ee1e4e865f7ce..c5bb87244dd72876d1ecf4be98196ef597dfc36d 100644 (file)
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1138,6 +1138,8 @@ static void balloon_up(struct work_struct *dummy)
        bool alloc_error;
        bool done = false;
        int i;
+       struct sysinfo val;
+       unsigned long floor;
 
        /* The host balloons pages in 2M granularity. */
        WARN_ON_ONCE(num_pages % PAGES_IN_2M != 0);
@@ -1148,6 +1150,15 @@ static void balloon_up(struct work_struct *dummy)
         */
        alloc_unit = 512;
 
+       si_meminfo(&val);
+       floor = compute_balloon_floor();
+
+       /* Refuse to balloon below the floor, keep the 2M granularity. */
+       if (val.freeram - num_pages < floor) {
+               num_pages = val.freeram > floor ? (val.freeram - floor) : 0;
+               num_pages -= num_pages % PAGES_IN_2M;
+       }
+
        while (!done) {
                bl_resp = (struct dm_balloon_response *)send_buffer;
                memset(send_buffer, 0, PAGE_SIZE);