[Xen-devel] [PATCH v2 06/18] mini-os: let memory allocation fail if no free page available

[Juergen Gross <jgross@xxxxxxxx>]

Instead of panicing when no page can be allocated try to fail the
memory allocation by returning NULL instead.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
V2: fixed minor style issue
---
 mm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm.c b/mm.c
index 263a356..8cf3210 100644
--- a/mm.c
+++ b/mm.c
@@ -335,6 +335,13 @@ void *sbrk(ptrdiff_t increment)
     
     if (new_brk > heap_mapped) {
         unsigned long n = (new_brk - heap_mapped + PAGE_SIZE - 1) / PAGE_SIZE;
+
+        if ( n > nr_free_pages )
+        {
+            printk("Memory exhausted: want %ld pages, but only %ld are left\n",
+                   n, nr_free_pages);
+            return NULL;
+        }
         do_map_zero(heap_mapped, n);
         heap_mapped += n * PAGE_SIZE;
     }
-- 
2.6.6


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