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Message-ID: <0215a42b-99cd-612a-95f7-56f8251d99ef@google.com>
Date: Sun, 31 Aug 2025 02:11:33 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Will Deacon <will@...nel.org>, David Hildenbrand <david@...hat.com>,
Shivank Garg <shivankg@....com>, Matthew Wilcox <willy@...radead.org>,
Christoph Hellwig <hch@...radead.org>, Keir Fraser <keirf@...gle.com>,
Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
Frederick Mayle <fmayle@...gle.com>, Peter Xu <peterx@...hat.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
Johannes Weiner <hannes@...xchg.org>, Vlastimil Babka <vbabka@...e.cz>,
Alexander Krabler <Alexander.Krabler@...a.com>,
Ge Yang <yangge1116@....com>, Li Zhe <lizhe.67@...edance.com>,
Chris Li <chrisl@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>,
Konstantin Khlebnikov <koct9i@...il.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH 4/7] mm: Revert "mm/gup: clear the LRU flag of a page before
adding to LRU batch"
This reverts commit 33dfe9204f29b415bbc0abb1a50642d1ba94f5e9:
now that collect_longterm_unpinnable_folios() is checking ref_count
instead of lru, and mlock/munlock do not participate in the revised
LRU flag clearing, those changes are misleading, and enlarge the
window during which mlock/munlock may miss an mlock_count update.
It is possible (I'd hesitate to claim probable) that the greater
likelihood of missed mlock_count updates would explain the "Realtime
threads delayed due to kcompactd0" observed on 6.12 in the Link below.
If that is the case, this reversion will help; but a complete solution
needs also a further patch, beyond the scope of this series.
Included some 80-column cleanup around folio_batch_add_and_move().
The role of folio_test_clear_lru() (before taking per-memcg lru_lock)
is questionable since 6.13 removed mem_cgroup_move_account() etc; but
perhaps there are still some races which need it - not examined here.
Link: https://lore.kernel.org/linux-mm/DU0PR01MB10385345F7153F334100981888259A@DU0PR01MB10385.eurprd01.prod.exchangelabs.com/
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
---
mm/swap.c | 50 ++++++++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 24 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 3632dd061beb..6ae2d5680574 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -164,6 +164,10 @@ static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
for (i = 0; i < folio_batch_count(fbatch); i++) {
struct folio *folio = fbatch->folios[i];
+ /* block memcg migration while the folio moves between lru */
+ if (move_fn != lru_add && !folio_test_clear_lru(folio))
+ continue;
+
folio_lruvec_relock_irqsave(folio, &lruvec, &flags);
move_fn(lruvec, folio);
@@ -176,14 +180,10 @@ static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
}
static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
- struct folio *folio, move_fn_t move_fn,
- bool on_lru, bool disable_irq)
+ struct folio *folio, move_fn_t move_fn, bool disable_irq)
{
unsigned long flags;
- if (on_lru && !folio_test_clear_lru(folio))
- return;
-
folio_get(folio);
if (disable_irq)
@@ -191,8 +191,8 @@ static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
else
local_lock(&cpu_fbatches.lock);
- if (!folio_batch_add(this_cpu_ptr(fbatch), folio) || folio_test_large(folio) ||
- lru_cache_disabled())
+ if (!folio_batch_add(this_cpu_ptr(fbatch), folio) ||
+ folio_test_large(folio) || lru_cache_disabled())
folio_batch_move_lru(this_cpu_ptr(fbatch), move_fn);
if (disable_irq)
@@ -201,13 +201,13 @@ static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
local_unlock(&cpu_fbatches.lock);
}
-#define folio_batch_add_and_move(folio, op, on_lru) \
- __folio_batch_add_and_move( \
- &cpu_fbatches.op, \
- folio, \
- op, \
- on_lru, \
- offsetof(struct cpu_fbatches, op) >= offsetof(struct cpu_fbatches, lock_irq) \
+#define folio_batch_add_and_move(folio, op) \
+ __folio_batch_add_and_move( \
+ &cpu_fbatches.op, \
+ folio, \
+ op, \
+ offsetof(struct cpu_fbatches, op) >= \
+ offsetof(struct cpu_fbatches, lock_irq) \
)
static void lru_move_tail(struct lruvec *lruvec, struct folio *folio)
@@ -231,10 +231,10 @@ static void lru_move_tail(struct lruvec *lruvec, struct folio *folio)
void folio_rotate_reclaimable(struct folio *folio)
{
if (folio_test_locked(folio) || folio_test_dirty(folio) ||
- folio_test_unevictable(folio))
+ folio_test_unevictable(folio) || !folio_test_lru(folio))
return;
- folio_batch_add_and_move(folio, lru_move_tail, true);
+ folio_batch_add_and_move(folio, lru_move_tail);
}
void lru_note_cost_unlock_irq(struct lruvec *lruvec, bool file,
@@ -328,10 +328,11 @@ static void folio_activate_drain(int cpu)
void folio_activate(struct folio *folio)
{
- if (folio_test_active(folio) || folio_test_unevictable(folio))
+ if (folio_test_active(folio) || folio_test_unevictable(folio) ||
+ !folio_test_lru(folio))
return;
- folio_batch_add_and_move(folio, lru_activate, true);
+ folio_batch_add_and_move(folio, lru_activate);
}
#else
@@ -507,7 +508,7 @@ void folio_add_lru(struct folio *folio)
lru_gen_in_fault() && !(current->flags & PF_MEMALLOC))
folio_set_active(folio);
- folio_batch_add_and_move(folio, lru_add, false);
+ folio_batch_add_and_move(folio, lru_add);
}
EXPORT_SYMBOL(folio_add_lru);
@@ -685,13 +686,13 @@ void lru_add_drain_cpu(int cpu)
void deactivate_file_folio(struct folio *folio)
{
/* Deactivating an unevictable folio will not accelerate reclaim */
- if (folio_test_unevictable(folio))
+ if (folio_test_unevictable(folio) || !folio_test_lru(folio))
return;
if (lru_gen_enabled() && lru_gen_clear_refs(folio))
return;
- folio_batch_add_and_move(folio, lru_deactivate_file, true);
+ folio_batch_add_and_move(folio, lru_deactivate_file);
}
/*
@@ -704,13 +705,13 @@ void deactivate_file_folio(struct folio *folio)
*/
void folio_deactivate(struct folio *folio)
{
- if (folio_test_unevictable(folio))
+ if (folio_test_unevictable(folio) || !folio_test_lru(folio))
return;
if (lru_gen_enabled() ? lru_gen_clear_refs(folio) : !folio_test_active(folio))
return;
- folio_batch_add_and_move(folio, lru_deactivate, true);
+ folio_batch_add_and_move(folio, lru_deactivate);
}
/**
@@ -723,10 +724,11 @@ void folio_deactivate(struct folio *folio)
void folio_mark_lazyfree(struct folio *folio)
{
if (!folio_test_anon(folio) || !folio_test_swapbacked(folio) ||
+ !folio_test_lru(folio) ||
folio_test_swapcache(folio) || folio_test_unevictable(folio))
return;
- folio_batch_add_and_move(folio, lru_lazyfree, true);
+ folio_batch_add_and_move(folio, lru_lazyfree);
}
void lru_add_drain(void)
--
2.51.0
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