on 8/15/2023 4:38 PM, Baolin Wang wrote:
>
>
> On 8/5/2023 7:07 PM, Kemeng Shi wrote:
>> We call isolate_freepages_block in strict mode, continuous pages in
>> pageblock will be isolated if isolate_freepages_block successed.
>> Then pfn + isolated will point to start of next pageblock to scan
>> no matter how many pageblocks are isolated in isolate_freepages_block.
>> Use pfn + isolated as start of next pageblock to scan to simplify the
>> iteration.
>
> IIUC, the isolate_freepages_block() can isolate high-order free pages, which means the pfn + isolated can be larger than the block_end_pfn. So in your patch, the 'block_start_pfn' and 'block_end_pfn' can be in different pageblocks, that will break pageblock_pfn_to_page().
>
In for update statement, we always update block_start_pfn to pfn and
update block_end_pfn to pfn + pageblock_nr_pages. So they should point
to the same pageblock. I guess you missed the change to update of
block_end_pfn. :)
>>
>> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
>> ---
>> mm/compaction.c | 14 ++------------
>> 1 file changed, 2 insertions(+), 12 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 684f6e6cd8bc..8d7d38073d30 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -733,21 +733,11 @@ isolate_freepages_range(struct compact_control *cc,
>> block_end_pfn = pageblock_end_pfn(pfn);
>> for (; pfn < end_pfn; pfn += isolated,
>> - block_start_pfn = block_end_pfn,
>> - block_end_pfn += pageblock_nr_pages) {
>> + block_start_pfn = pfn,
>> + block_end_pfn = pfn + pageblock_nr_pages) {
>> /* Protect pfn from changing by isolate_freepages_block */
>> unsigned long isolate_start_pfn = pfn;
>> - /*
>> - * pfn could pass the block_end_pfn if isolated freepage
>> - * is more than pageblock order. In this case, we adjust
>> - * scanning range to right one.
>> - */
>> - if (pfn >= block_end_pfn) {
>> - block_start_pfn = pageblock_start_pfn(pfn);
>> - block_end_pfn = pageblock_end_pfn(pfn);
>> - }
>> -
>> block_end_pfn = min(block_end_pfn, end_pfn);
>> if (!pageblock_pfn_to_page(block_start_pfn,
>
