Re: [PATCH v9] mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks

[KOSAKI Motohiro <kosaki.motohiro@gmail.com>]

> +/*
> + * Returns true if MIGRATE_UNMOVABLE pageblock can be successfully
> + * converted to MIGRATE_MOVABLE type, false otherwise.
> + */
> +static bool can_rescue_unmovable_pageblock(struct page *page, bool locked)
> +{
> +	unsigned long pfn, start_pfn, end_pfn;
> +	struct page *start_page, *end_page, *cursor_page;
> +
> +	pfn = page_to_pfn(page);
> +	start_pfn = pfn&  ~(pageblock_nr_pages - 1);
> +	end_pfn = start_pfn + pageblock_nr_pages - 1;
> +
> +	start_page = pfn_to_page(start_pfn);
> +	end_page = pfn_to_page(end_pfn);
> +
> +	for (cursor_page = start_page, pfn = start_pfn; cursor_page<= end_page;
> +		pfn++, cursor_page++) {
> +		struct zone *zone = page_zone(start_page);
> +		unsigned long flags;
> +
> +		if (!pfn_valid_within(pfn))
> +			continue;
> +
> +		/* Do not deal with pageblocks that overlap zones */
> +		if (page_zone(cursor_page) != zone)
> +			return false;
> +
> +		if (!locked)
> +			spin_lock_irqsave(&zone->lock, flags);
> +
> +		if (PageBuddy(cursor_page)) {
> +			int order = page_order(cursor_page);
>
> -/* Returns true if the page is within a block suitable for migration to */
> -static bool suitable_migration_target(struct page *page)
> +			pfn += (1<<  order) - 1;
> +			cursor_page += (1<<  order) - 1;
> +
> +			if (!locked)
> +				spin_unlock_irqrestore(&zone->lock, flags);
> +			continue;
> +		} else if (page_count(cursor_page) == 0 ||
> +			   PageLRU(cursor_page)) {
> +			if (!locked)
> +				spin_unlock_irqrestore(&zone->lock, flags);
> +			continue;
> +		}
> +
> +		if (!locked)
> +			spin_unlock_irqrestore(&zone->lock, flags);
> +
> +		return false;
> +	}
> +
> +	return true;
> +}

Minchan, are you interest this patch? If yes, can you please rewrite it? This one are
not fixed our pointed issue and can_rescue_unmovable_pageblock() still has plenty bugs.
We can't ack it.

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