Re: [PATCH v2 3/7] mm/compaction: correctly return failure with bogus compound_order in strict mode

[Mel Gorman]

On Sat, Aug 26, 2023 at 11:36:13PM +0800, Kemeng Shi wrote:
> In strict mode, we should return 0 if there is any hole in pageblock. If
> we successfully isolated pages at beginning at pageblock and then have a
> bogus compound_order outside pageblock in next page. We will abort search
> loop with blockpfn > end_pfn. Although we will limit blockpfn to end_pfn,
> we will treat it as a successful isolation in strict mode as blockpfn is
> not < end_pfn and return partial isolated pages. Then
> isolate_freepages_range may success unexpectly with hole in isolated
> range.
> 
> Fixes: 9fcd6d2e052ee ("mm, compaction: skip compound pages by order in free scanner")
> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>

Modify the (likely(order <= MAX_ORDER)) block to avoid ever updating
blockpfn past the end of the pageblock. Then remove the second redundant
check.

-- 
Mel Gorman
SUSE Labs