On 5/25/23 14:53, Baolin Wang wrote: > In fast_isolate_around(), it assumes the pageblock is fully scanned if > cc->nr_freepages < cc->nr_migratepages after trying to isolate some free > pages, and will set skip flag to avoid scanning in future. However this > can miss setting the skip flag for a fully scanned pageblock (returned > 'start_pfn' is equal to 'end_pfn') in the case where cc->nr_freepages > is larger than cc->nr_migratepages. > > So using the returned 'start_pfn' from isolate_freepages_block() and > 'end_pfn' to decide if a pageblock is fully scanned makes more sense. > It can also cover the case where cc->nr_freepages < cc->nr_migratepages, > which means the 'start_pfn' is usually equal to 'end_pfn' except some > uncommon fatal error occurs after non-strict mode isolation. > > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > mm/compaction.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 3737c6591bfb..1e5183f39ca9 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1411,7 +1411,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn) > isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); > > /* Skip this pageblock in the future as it's full or nearly full */ > - if (cc->nr_freepages < cc->nr_migratepages) > + if (start_pfn == end_pfn) > set_pageblock_skip(page); > > return;
