[PATCH 1/1] xen/mm: normalize page count types to unsigned long

[Bernhard Kaindl <bernhard.kaindl@xxxxxxxxxx>]

The current use of long for total_avail_pages and outstanding_claims
creates an unnecessary mix of signed and unsigned types during page
allocation calculations. This necessitates awkward constructs
like '+ 0UL' to satisfy type matching in macros such as min().

Address this by normalizing `total_avail_pages` and `outstanding_claims`
from `long` to `unsigned long`.

As a direct consequence of making `total_avail_pages` unsigned, the
post-decrement assertions checking for `>= 0` are no longer logically
sound. Adjust those assertions to pre-decrement checks.

No functional change intended.

Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Bernhard Kaindl <bernhard.kaindl@xxxxxxxxxx>
---
 xen/common/page_alloc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index b1edef87124f..541a2171c4c5 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -484,10 +484,11 @@ static heap_by_zone_and_order_t *_heap[MAX_NUMNODES];
 static unsigned long node_need_scrub[MAX_NUMNODES];
 
 static unsigned long *avail[MAX_NUMNODES];
-static long total_avail_pages;
+static unsigned long total_avail_pages;
 
 static DEFINE_SPINLOCK(heap_lock);
-static long outstanding_claims; /* total outstanding claims by all domains */
+/* total outstanding claims by all domains */
+static unsigned long outstanding_claims;
 
 static unsigned long avail_heap_pages(
     unsigned int zone_lo, unsigned int zone_hi, unsigned int node)
@@ -1047,8 +1048,8 @@ static struct page_info *alloc_heap_pages(
 
     ASSERT(avail[node][zone] >= request);
     avail[node][zone] -= request;
+    ASSERT(total_avail_pages >= request);
     total_avail_pages -= request;
-    ASSERT(total_avail_pages >= 0);
 
     if ( d && d->outstanding_pages && !(memflags & MEMF_no_refcount) )
     {
@@ -1240,8 +1241,8 @@ static int reserve_offlined_page(struct page_info *head)
             continue;
 
         avail[node][zone]--;
+        ASSERT(total_avail_pages > 0);
         total_avail_pages--;
-        ASSERT(total_avail_pages >= 0);
 
         page_list_add_tail(cur_head,
                            test_bit(_PGC_broken, &cur_head->count_info) ?
-- 
2.39.5