diff mbox series

[V3] mm/swap: take folio refcount after testing the LRU flag

Message ID 1723542743-32179-1-git-send-email-yangge1116@126.com (mailing list archive)
State New
Headers show
Series [V3] mm/swap: take folio refcount after testing the LRU flag | expand

Commit Message

Ge Yang Aug. 13, 2024, 9:52 a.m. UTC 
From: yangge <yangge1116@126.com>

Whoever passes a folio to __folio_batch_add_and_move() must hold
a reference, otherwise something else would already be messed up.
If the folio is referenced, it will not be freed elsewhere, so we
can safely clear the folio's lru flag. As discussed with David
in [1], we should take the reference after testing the LRU flag,
not before.

Link: https://lore.kernel.org/lkml/d41865b4-d6fa-49ba-890a-921eefad27dd@redhat.com/ [1]
Signed-off-by: yangge <yangge1116@126.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
 mm/swap.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

V3:
   Remove sanity check suggested by Yu
V2:
   Add sanity check suggested by David
diff mbox series

Patch

diff --git a/mm/swap.c b/mm/swap.c
index 67a2467..6b83898 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -226,12 +226,10 @@  static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
 {
 	unsigned long flags;
 
-	folio_get(folio);
-
-	if (on_lru && !folio_test_clear_lru(folio)) {
-		folio_put(folio);
+	if (on_lru && !folio_test_clear_lru(folio))
 		return;
-	}
+
+	folio_get(folio);
 
 	if (disable_irq)
 		local_lock_irqsave(&cpu_fbatches.lock_irq, flags);