On 2024/8/28 18:04, Baolin Wang wrote:
Hi Kefeng,
On 2024/8/26 12:01, Kefeng Wang wrote:
The tail page will always fail to isolate for non-lru-movable and
LRU page in isolate_migratepages_block(), so move PageTail check
ahead, then convert to use folio_isolate_movable() helper and more
folios.
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
mm/compaction.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index a2b16b08cbbf..aa2e8bb9fa58 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1074,39 +1074,41 @@ isolate_migratepages_block(struct
compact_control *cc, unsigned long low_pfn,
}
}
+ if (PageTail(page))
+ goto isolate_fail;
+
+ folio = page_folio(page);
I wonder if this is stable. Before page_folio(), it does not hold a
reference on the page, so seems we should re-check the folio still
contains this page after gaining a reference on the folio?
Oh, you are right, so two way to avoid this,
1) re-check 'page_folio(page) == folio', but this need change a little
more.
2) directly use folio_get_nontail_page(page) here, and folio_put in the
following path, this will try to get for any pages, but it should be
accepted ?
I'd prefer 2) but any other suggestion?
Thanks.
/*
* Check may be lockless but that's ok as we recheck later.
- * It's possible to migrate LRU and non-lru movable pages.
- * Skip any other type of page
+ * It's possible to migrate LRU and non-lru movable folioss.
+ * Skip any other type of folios.
*/
- if (!PageLRU(page)) {
+ if (!folio_test_lru(folio)) {
/*
- * __PageMovable can return false positive so we need
- * to verify it under page_lock.
+ * __folio_test_movable can return false positive so
+ * we need to verify it under page_lock.
*/
- if (unlikely(__PageMovable(page)) &&
- !PageIsolated(page)) {
+ if (unlikely(__folio_test_movable(folio)) &&
+ !folio_test_isolated(folio)) {
if (locked) {
unlock_page_lruvec_irqrestore(locked, flags);
locked = NULL;
}
- if (isolate_movable_page(page, mode)) {
- folio = page_folio(page);
+ if (folio_isolate_movable(folio, mode))
goto isolate_success;
- }
}
goto isolate_fail;
}
/*
- * Be careful not to clear PageLRU until after we're
- * sure the page is not being freed elsewhere -- the
- * page release code relies on it.
+ * Be careful not to clear lru flag until after we're
+ * sure the folio is not being freed elsewhere -- the
+ * folio release code relies on it.
*/
- folio = folio_get_nontail_page(page);
- if (unlikely(!folio))
+ if (unlikely(folio_try_get(folio)))
goto isolate_fail;
/*
