On 2024/8/29 07:37, Vishal Moola wrote:
On Wed, Aug 28, 2024 at 08:36:03PM +0800, Kefeng Wang wrote:
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?
I think option 2 makes sense, and simply use folio_put() on success and
goto isolate_fail_put on failure instead of isolate_fail.
With option 2, it might make sense to have folio_isolate_movable()
expect to be passed a folio with elevated refcount. Then it could be
treated similarly to its sister function folio_isolate_lru() and simply
use folio_get() for its reference.
Yes, that makes sense to me too.
