vmw_balloon: refactor change size from vmballoon_work

The required change in the balloon size is currently computed in
vmballoon_work(), vmballoon_inflate() and vmballoon_deflate(). Refactor
it to simplify the next patches.

Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 626abe65eddb3471cdda56ab9dd232b5c047c6c5..0d9f223d463e25e9341adb48ae1914b25421ab8d 100644 (file)
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -633,6 +633,37 @@ static void vmballoon_add_page(struct vmballoon *b, int idx, struct page *p)
                b->page = p;
 }
 
+/**
+ * vmballoon_change - retrieve the required balloon change
+ *
+ * @b: pointer for the balloon.
+ *
+ * Return: the required change for the balloon size. A positive number
+ * indicates inflation, a negative number indicates a deflation.
+ */
+static int64_t vmballoon_change(struct vmballoon *b)
+{
+       int64_t size, target;
+
+       size = b->size;
+       target = b->target;
+
+       /*
+        * We must cast first because of int sizes
+        * Otherwise we might get huge positives instead of negatives
+        */
+
+       if (b->reset_required)
+               return 0;
+
+       /* consider a 2MB slack on deflate, unless the balloon is emptied */
+       if (target < size && size - target < vmballoon_page_size(true) &&
+           target != 0)
+               return 0;
+
+       return target - size;
+}
+
 /*
  * Inflate the balloon towards its target size. Note that we try to limit
  * the rate of allocation to make sure we are not choking the rest of the
@@ -644,8 +675,6 @@ static void vmballoon_inflate(struct vmballoon *b)
        int error = 0;
        bool is_2m_pages;
 
-       pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
-
        /*
         * First try NOSLEEP page allocations to inflate balloon.
         *
@@ -667,11 +696,8 @@ static void vmballoon_inflate(struct vmballoon *b)
         */
        is_2m_pages = b->supported_page_sizes == VMW_BALLOON_NUM_PAGE_SIZES;
 
-       pr_debug("%s - goal: %d",  __func__, b->target - b->size);
-
-       while (!b->reset_required &&
-               b->size + num_pages * vmballoon_page_size(is_2m_pages)
-               < b->target) {
+       while ((int64_t)(num_pages * vmballoon_page_size(is_2m_pages)) <
+              vmballoon_change(b)) {
                struct page *page;
 
                STATS_INC(b->stats.alloc[is_2m_pages]);
@@ -742,8 +768,6 @@ static void vmballoon_deflate(struct vmballoon *b)
 {
        unsigned is_2m_pages;
 
-       pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
-
        /* free pages to reach target */
        for (is_2m_pages = 0; is_2m_pages < b->supported_page_sizes;
                        is_2m_pages++) {
@@ -753,11 +777,9 @@ static void vmballoon_deflate(struct vmballoon *b)
                                &b->page_sizes[is_2m_pages];
 
                list_for_each_entry_safe(page, next, &page_size->pages, lru) {
-                       if (b->reset_required ||
-                               (b->target > 0 &&
-                                       b->size - num_pages
-                                       * vmballoon_page_size(is_2m_pages)
-                               < b->target + vmballoon_page_size(true)))
+                       if ((int64_t)(num_pages *
+                                     vmballoon_page_size(is_2m_pages)) >=
+                                       -vmballoon_change(b))
                                break;
 
                        list_del(&page->lru);
@@ -921,28 +943,35 @@ static void vmballoon_reset(struct vmballoon *b)
                pr_err("failed to send guest ID to the host\n");
 }
 
-/*
- * Balloon work function: reset protocol, if needed, get the new size and
- * adjust balloon as needed. Repeat in 1 sec.
+/**
+ * vmballoon_work - periodic balloon worker for reset, inflation and deflation.
+ *
+ * @work: pointer to the &work_struct which is provided by the workqueue.
+ *
+ * Resets the protocol if needed, gets the new size and adjusts balloon as
+ * needed. Repeat in 1 sec.
  */
 static void vmballoon_work(struct work_struct *work)
 {
        struct delayed_work *dwork = to_delayed_work(work);
        struct vmballoon *b = container_of(dwork, struct vmballoon, dwork);
+       int64_t change = 0;
 
        STATS_INC(b->stats.timer);
 
        if (b->reset_required)
                vmballoon_reset(b);
 
-       if (!b->reset_required && vmballoon_send_get_target(b)) {
-               unsigned long target = b->target;
+       if (vmballoon_send_get_target(b))
+               change = vmballoon_change(b);
+
+       if (change != 0) {
+               pr_debug("%s - size: %u, target %u", __func__,
+                        b->size, b->target);
 
-               /* update target, adjust size */
-               if (b->size < target)
+               if (change > 0)
                        vmballoon_inflate(b);
-               else if (target == 0 ||
-                               b->size > target + vmballoon_page_size(true))
+               else  /* (change < 0) */
                        vmballoon_deflate(b);
        }