avoid endless loops in lib/swiotlb.c
[linux-2.6.git] / lib / swiotlb.c
index 4bb5a11..0259228 100644 (file)
@@ -310,7 +310,9 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
        start_dma_addr = virt_to_bus(io_tlb_start) & mask;
 
        offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
-       max_slots = ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+       max_slots = mask + 1
+                   ? ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT
+                   : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
 
        /*
         * For mappings greater than a page, we limit the stride (and
@@ -333,16 +335,18 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
                index = ALIGN(io_tlb_index, stride);
                if (index >= io_tlb_nslabs)
                        index = 0;
-
-               while (is_span_boundary(index, nslots, offset_slots,
-                                       max_slots)) {
-                       index += stride;
-                       if (index >= io_tlb_nslabs)
-                               index = 0;
-               }
                wrap = index;
 
                do {
+                       while (is_span_boundary(index, nslots, offset_slots,
+                                               max_slots)) {
+                               index += stride;
+                               if (index >= io_tlb_nslabs)
+                                       index = 0;
+                               if (index == wrap)
+                                       goto not_found;
+                       }
+
                        /*
                         * If we find a slot that indicates we have 'nslots'
                         * number of contiguous buffers, we allocate the
@@ -367,14 +371,12 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
 
                                goto found;
                        }
-                       do {
-                               index += stride;
-                               if (index >= io_tlb_nslabs)
-                                       index = 0;
-                       } while (is_span_boundary(index, nslots, offset_slots,
-                                                 max_slots));
+                       index += stride;
+                       if (index >= io_tlb_nslabs)
+                               index = 0;
                } while (index != wrap);
 
+  not_found:
                spin_unlock_irqrestore(&io_tlb_lock, flags);
                return NULL;
        }