The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x bb5e7f234eacf34b65be67ebb3613e3b8cf11b87 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023091354-atom-tinderbox-b9be@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: bb5e7f234eac ("Multi-gen LRU: avoid race in inc_min_seq()") 391655fe08d1 ("mm: multi-gen LRU: rename lru_gen_struct to lru_gen_folio") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From bb5e7f234eacf34b65be67ebb3613e3b8cf11b87 Mon Sep 17 00:00:00 2001 From: Kalesh Singh <kaleshsingh@xxxxxxxxxx> Date: Tue, 1 Aug 2023 19:56:03 -0700 Subject: [PATCH] Multi-gen LRU: avoid race in inc_min_seq() 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> diff --git a/mm/vmscan.c b/mm/vmscan.c index 489a4fc7d9b1..6eecd291756c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4439,7 +4439,7 @@ static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan) int prev, next; int type, zone; struct lru_gen_folio *lrugen = &lruvec->lrugen; - +restart: spin_lock_irq(&lruvec->lru_lock); VM_WARN_ON_ONCE(!seq_is_valid(lruvec)); @@ -4450,11 +4450,12 @@ static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan) 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; } /*
