[Xen-devel] [PATCH v2 2/2] make domain_adjust_tot_pages() __must_check

["Jan Beulich" <JBeulich@xxxxxxxx>]

Even if unlikely, donate_page() should not ignore the possible need to
obtain a domain reference. To make people look more closely when they
add new uses of domain_adjust_tot_pages(), force its return value to be
checked. This in turn requires a benign change to assign_pages().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4009,7 +4009,8 @@ int donate_page(
     {
         if ( d->tot_pages >= d->max_pages )
             goto fail;
-        domain_adjust_tot_pages(d, 1);
+        if ( unlikely(domain_adjust_tot_pages(d, 1) == 1) )
+            get_knownalive_domain(d);
     }
 
     page->count_info = PGC_allocated | 1;
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2273,10 +2273,8 @@ int assign_pages(
             goto out;
         }
 
-        if ( unlikely(d->tot_pages == 0) )
+        if ( unlikely(domain_adjust_tot_pages(d, 1 << order) == (1 << order)) )
             get_knownalive_domain(d);
-
-        domain_adjust_tot_pages(d, 1 << order);
     }
 
     for ( i = 0; i < (1 << order); i++ )
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -190,7 +190,8 @@ int destroy_xen_mappings(unsigned long v
  */
 int populate_pt_range(unsigned long virt, unsigned long nr_mfns);
 /* Claim handling */
-unsigned long domain_adjust_tot_pages(struct domain *d, long pages);
+unsigned long __must_check domain_adjust_tot_pages(struct domain *d,
+    long pages);
 int domain_set_outstanding_pages(struct domain *d, unsigned long pages);
 void get_outstanding_claims(uint64_t *free_pages, uint64_t *outstanding_pages);
 





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