The quilt patch titled
Subject: mm: lock PGDAT_RECLAIM_LOCKED with acquire memory ordering
has been removed from the -mm tree. Its filename was
mm-lock-pgdat_reclaim_locked-with-acquire-memory-ordering.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Subject: mm: lock PGDAT_RECLAIM_LOCKED with acquire memory ordering
Date: Wed, 12 Mar 2025 10:10:14 -0400
The PGDAT_RECLAIM_LOCKED bit is used to provide mutual exclusion of node
reclaim for struct pglist_data using a single bit.
Use test_and_set_bit_lock rather than test_and_set_bit to test-and-set
PGDAT_RECLAIM_LOCKED with an acquire memory ordering semantic.
This changes the "lock" acquisition from a full barrier to an acquire
memory ordering, which is weaker. The acquire semi-permeable barrier
paired with the release on unlock is sufficient for this mutual exclusion
use-case.
No behavior change intended other than to reduce overhead by using the
appropriate barrier.
Link: https://lkml.kernel.org/r/20250312141014.129725-2-mathieu.desnoyers@xxxxxxxxxxxx
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Parri <parri.andrea@xxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Jade Alglave <j.alglave@xxxxxxxxx>
Cc: Luc Maranget <luc.maranget@xxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmscan.c~mm-lock-pgdat_reclaim_locked-with-acquire-memory-ordering
+++ a/mm/vmscan.c
@@ -7577,7 +7577,7 @@ int node_reclaim(struct pglist_data *pgd
if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
return NODE_RECLAIM_NOSCAN;
- if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
+ if (test_and_set_bit_lock(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
return NODE_RECLAIM_NOSCAN;
ret = __node_reclaim(pgdat, gfp_mask, order);
_
Patches currently in -mm which might be from mathieu.desnoyers@xxxxxxxxxxxx are
