bitkeeper revision 1.1213 (42137438B9PrvSq_PgHTjzbXpJ1YhA)

xmalloc.c:
  Fix xmalloc allocator to not merge across page boundaries.
  Signed-off-by: Keir Fraser <keir@xensource.com>

diff --git a/xen/common/xmalloc.c b/xen/common/xmalloc.c
index 8addc7e4d01780f33070cd7444ad95926ad05737..86ff1b32b49a1c8fd7aea43c503b7052d97f642c 100644 (file)
--- a/xen/common/xmalloc.c
+++ b/xen/common/xmalloc.c
@@ -25,7 +25,7 @@
 #include <xen/ac_timer.h>
 #include <xen/cache.h>
 
-#define BUG_ON(x) do { if (x) BUG(); }while(0)
+#define BUG_ON(x) do { if (x) BUG(); } while(0)
 
 static LIST_HEAD(freelist);
 static spinlock_t freelist_lock = SPIN_LOCK_UNLOCKED;
@@ -48,8 +48,9 @@ static void maybe_split(struct xmalloc_hdr *hdr, size_t size, size_t block)
                extra = (void *)hdr + size;
                extra->size = leftover;
                list_add(&extra->freelist, &freelist);
-       } else
+       } else {
                size = block;
+       }
 
        hdr->size = size;
        /* Debugging aid. */
@@ -62,7 +63,7 @@ static void *xmalloc_new_page(size_t size)
        unsigned long flags;
 
        hdr = (void *)alloc_xenheap_pages(0);
-       if (!hdr)
+       if (hdr == NULL)
                return NULL;
 
        spin_lock_irqsave(&freelist_lock, flags);
@@ -78,7 +79,7 @@ static void *xmalloc_whole_pages(size_t size)
        unsigned int pageorder = get_order(size);
 
        hdr = (void *)alloc_xenheap_pages(pageorder);
-       if (!hdr)
+       if (hdr == NULL)
                return NULL;
 
        hdr->size = (1 << (pageorder + PAGE_SHIFT));
@@ -130,7 +131,7 @@ void xfree(const void *p)
        unsigned long flags;
        struct xmalloc_hdr *i, *tmp, *hdr;
 
-       if (!p)
+       if (p == NULL)
                return;
 
        hdr = (struct xmalloc_hdr *)p - 1;
@@ -150,14 +151,19 @@ void xfree(const void *p)
        /* Merge with other free block, or put in list. */
        spin_lock_irqsave(&freelist_lock, flags);
        list_for_each_entry_safe(i, tmp, &freelist, freelist) {
+               unsigned long _i   = (unsigned long)i;
+               unsigned long _hdr = (unsigned long)hdr;
+               /* Do not merge across page boundaries. */
+               if (((_i ^ _hdr) & PAGE_MASK) != 0)
+                       continue;
                /* We follow this block?  Swallow it. */
-               if ((void *)i + i->size == (void *)hdr) {
+               if ((_i + i->size) == _hdr) {
                        list_del(&i->freelist);
                        i->size += hdr->size;
                        hdr = i;
                }
-               /* It follows us?  Delete it and add it to us. */
-               if ((void *)hdr + hdr->size == (void *)i) {
+               /* We precede this block? Swallow it. */
+               if ((_hdr + hdr->size) == _i) {
                        list_del(&i->freelist);
                        hdr->size += i->size;
                }
@@ -167,7 +173,9 @@ void xfree(const void *p)
        if (hdr->size == PAGE_SIZE) {
                BUG_ON((((unsigned long)hdr) & (PAGE_SIZE-1)) != 0);
                free_xenheap_pages((unsigned long)hdr, 0);
-       } else
+       } else {
                list_add(&hdr->freelist, &freelist);
+       }
+
        spin_unlock_irqrestore(&freelist_lock, flags);
 }