This is a note to let you know that I've just added the patch titled
Multi-gen LRU: avoid race in inc_min_seq()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
multi-gen-lru-avoid-race-in-inc_min_seq.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bb5e7f234eacf34b65be67ebb3613e3b8cf11b87 Mon Sep 17 00:00:00 2001
From: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Date: Tue, 1 Aug 2023 19:56:03 -0700
Subject: Multi-gen LRU: avoid race in inc_min_seq()
From: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
commit bb5e7f234eacf34b65be67ebb3613e3b8cf11b87 upstream.
inc_max_seq() will try to inc_min_seq() if nr_gens == MAX_NR_GENS. This
is because the generations are reused (the last oldest now empty
generation will become the next youngest generation).
inc_min_seq() is retried until successful, dropping the lru_lock
and yielding the CPU on each failure, and retaking the lock before
trying again:
while (!inc_min_seq(lruvec, type, can_swap)) {
spin_unlock_irq(&lruvec->lru_lock);
cond_resched();
spin_lock_irq(&lruvec->lru_lock);
}
However, the initial condition that required incrementing the min_seq
(nr_gens == MAX_NR_GENS) is not retested. This can change by another
call to inc_max_seq() from run_aging() with force_scan=true from the
debugfs interface.
Since the eviction stalls when the nr_gens == MIN_NR_GENS, avoid
unnecessarily incrementing the min_seq by rechecking the number of
generations before each attempt.
This issue was uncovered in previous discussion on the list by Yu Zhao
and Aneesh Kumar [1].
[1] https://lore.kernel.org/linux-mm/CAOUHufbO7CaVm=xjEb1avDhHVvnC8pJmGyKcFf2iY_dpf+zR3w@xxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20230802025606.346758-2-kaleshsingh@xxxxxxxxxx
Fixes: d6c3af7d8a2b ("mm: multi-gen LRU: debugfs interface")
Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> [mediatek]
Tested-by: Charan Teja Kalla <quic_charante@xxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: Brian Geffon <bgeffon@xxxxxxxxxx>
Cc: Jan Alexander Steffens (heftig) <heftig@xxxxxxxxxxxxx>
Cc: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Steven Barrett <steven@xxxxxxxxxxxx>
Cc: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4331,6 +4331,7 @@ static void inc_max_seq(struct lruvec *l
int type, zone;
struct lru_gen_struct *lrugen = &lruvec->lrugen;
+restart:
spin_lock_irq(&lruvec->lru_lock);
VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
@@ -4341,11 +4342,12 @@ static void inc_max_seq(struct lruvec *l
VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
- while (!inc_min_seq(lruvec, type, can_swap)) {
- spin_unlock_irq(&lruvec->lru_lock);
- cond_resched();
- spin_lock_irq(&lruvec->lru_lock);
- }
+ if (inc_min_seq(lruvec, type, can_swap))
+ continue;
+
+ spin_unlock_irq(&lruvec->lru_lock);
+ cond_resched();
+ goto restart;
}
/*
Patches currently in stable-queue which might be from kaleshsingh@xxxxxxxxxx are
queue-6.1/multi-gen-lru-fix-per-zone-reclaim.patch
queue-6.1/multi-gen-lru-avoid-race-in-inc_min_seq.patch
