For buddy system initialization, the holes between banks adjacent will be released to buddy allocator?

[Li Haifeng]

2012/8/27 Russell King - ARM Linux <linux at arm.linux.org.uk>:
> On Mon, Aug 27, 2012 at 10:42:40AM +0800, Li Haifeng wrote:
>> Just now, I tested it on my ARM development board.
>>
>> The holes between banks does be released to buddy allocator. And the
>> buddy system will allocate holes for thread, which will cause fault.
>> Is it right?
>
> Could you rephrase your question please?

The code below is to release free memory to buddy allocator, according
to node_bootmem_map.

The lines 180~181 get the low memory's range, and the range includes holes.
But while releasing the memory to buddy allocator, the code doesn't
prevent the holes from releasing to the buddy allocator. So, if the
holes are allocated to thread, fault will happen.

IMO, it is a bug. Is it right?

172 static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
173 {
174         struct page *page;
175         unsigned long start, end, pages, count = 0;
176
177         if (!bdata->node_bootmem_map)
178                 return 0;
179
180         start = bdata->node_min_pfn;
181         end = bdata->node_low_pfn;
182
183         bdebug("nid=%td start=%lx end=%lx\n",
184                 bdata - bootmem_node_data, start, end);
185
186         while (start < end) {
187                 unsigned long *map, idx, vec;
188
189                 map = bdata->node_bootmem_map;
190                 idx = start - bdata->node_min_pfn;
191                 vec = ~map[idx / BITS_PER_LONG];
192                 /*
193                  * If we have a properly aligned and fully unreserved
194                  * BITS_PER_LONG block of pages in front of us, free
195                  * it in one go.
196                  */
197                 if (IS_ALIGNED(start, BITS_PER_LONG) && vec == ~0UL) {
198                         int order = ilog2(BITS_PER_LONG);
199
200                         __free_pages_bootmem(pfn_to_page(start), order);
201                         count += BITS_PER_LONG;
202                         start += BITS_PER_LONG;
203                 } else {
204                         unsigned long off = 0;
205
206                         while (vec && off < BITS_PER_LONG) {
207                                 if (vec & 1) {
208                                         page = pfn_to_page(start + off);
209                                         __free_pages_bootmem(page, 0);
210                                         count++;
211                                 }
212                                 vec >>= 1;
213                                 off++;
214                         }
215                         start = ALIGN(start + 1, BITS_PER_LONG);
216                 }
217         }
218
219         page = virt_to_page(bdata->node_bootmem_map);
220         pages = bdata->node_low_pfn - bdata->node_min_pfn;
221         pages = bootmem_bootmap_pages(pages);
222         count += pages;
223         while (pages--)
224                 __free_pages_bootmem(page++, 0);
225
226         bdebug("nid=%td released=%lx\n", bdata - bootmem_node_data, count);
227
228         return count;
229 }