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Howlett" , Lian Wang , Lorenzo Stoakes , Michal Hocko , Muchun Song , Qi Zheng , Roman Gushchin , Shakeel Butt , Vlastimil Babka , Wei Xu , Yuanchu Xie , Yu Zhao , Zi Yan , Sasha Levin Subject: [PATCH 7.3.y 1/2] mm/mglru: use explicit tier range in read_ctrl_pos() Date: Tue, 10 Nov 2026 23:20:16 -0500 Message-ID: <20261111041806.1021595-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107050419-failed-7.3-ca6e32f3f424@kernel.org> References: <20261107050419-failed-7.3-ca6e32f3f424@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kairui Song [ Upstream commit c1d0e799321c817a22eab2abf2485250cffad7b4 ] read_ctrl_pos() encodes the tier range in a single "tier" parameter via "tier % MAX_NR_TIERS" as the start and "min(tier, MAX_NR_TIERS-1)" as the end. This is hard to follow, maintain, or extend. Tier values 0..3 select a single tier, while tier == MAX_NR_TIERS selects the full range. Replace it with explicit (tier_min, tier_max) parameters using a closed [tier_min, tier_max] interval, and add LRU_TIER_MIN and LRU_TIER_MAX for the tier bounds. The call sites now become self-documenting: - get_tier_idx: (LRU_TIER_MIN, LRU_TIER_MIN) for the first tier, (tier, tier) for each subsequent tier - get_type_to_scan: (LRU_TIER_MIN, LRU_TIER_MAX) for the full range No functional change. Link: https://lore.kernel.org/20260906-mglru-flags-cleanup-v6-5-9aacbd77d4ca@tencent.com Signed-off-by: Kairui Song Signed-off-by: Andrew Morton Reviewed-by: Baolin Wang Reviewed-by: Baoquan He Reviewed-by: Barry Song Reviewed-by: Ridong Chen Cc: Axel Rasmussen Cc: Chris Li Cc: David Hildenbrand (Arm) Cc: Johannes Weiner Cc: Kairui Song Cc: Liam R. Howlett Cc: Lian Wang Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Muchun Song Cc: Qi Zheng Cc: Roman Gushchin Cc: Shakeel Butt Cc: Vlastimil Babka Cc: Wei Xu Cc: Yuanchu Xie Cc: Yu Zhao Cc: Zi Yan Stable-dep-of: ca6e32f3f424 ("mm/vmscan: avoid false-positive -Wuninitialized warning, again") Signed-off-by: Sasha Levin --- include/linux/mmzone.h | 2 ++ mm/vmscan.c | 18 ++++++++++-------- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 94f9c3ff54160..da8dd04fb462a 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -492,6 +492,8 @@ enum lruvec_flags { * folio->flags, masked by LRU_REFS_MASK. */ #define MAX_NR_TIERS 4U +#define LRU_TIER_MIN 0U +#define LRU_TIER_MAX (MAX_NR_TIERS - 1) #ifndef __GENERATING_BOUNDS_H diff --git a/mm/vmscan.c b/mm/vmscan.c index 963cdd67039d1..8ec8fdede5dd8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3194,8 +3194,8 @@ struct ctrl_pos { int gain; }; -static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, - struct ctrl_pos *pos) +static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min, + int tier_max, int gain, struct ctrl_pos *pos) { int i; struct lru_gen_folio *lrugen = &lruvec->lrugen; @@ -3204,7 +3204,7 @@ static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, pos->gain = gain; pos->refaulted = pos->total = 0; - for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) { + for (i = tier_min; i <= tier_max; i++) { pos->refaulted += lrugen->avg_refaulted[type][i] + atomic_long_read(&lrugen->refaulted[hist][type][i]); pos->total += lrugen->avg_total[type][i] + @@ -4808,9 +4808,9 @@ static int get_tier_idx(struct lruvec *lruvec, int type) * This value is chosen because any other tier would have at least twice * as many refaults as the first tier. */ - read_ctrl_pos(lruvec, type, 0, 2, &sp); - for (tier = 1; tier < MAX_NR_TIERS; tier++) { - read_ctrl_pos(lruvec, type, tier, 3, &pv); + read_ctrl_pos(lruvec, type, LRU_TIER_MIN, LRU_TIER_MIN, 2, &sp); + for (tier = LRU_TIER_MIN + 1; tier <= LRU_TIER_MAX; tier++) { + read_ctrl_pos(lruvec, type, tier, tier, 3, &pv); if (!positive_ctrl_err(&sp, &pv)) break; } @@ -4831,8 +4831,10 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness) * Compare the sum of all tiers of anon with that of file to determine * which type to scan. */ - read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp); - read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv); + read_ctrl_pos(lruvec, LRU_GEN_ANON, LRU_TIER_MIN, LRU_TIER_MAX, + swappiness, &sp); + read_ctrl_pos(lruvec, LRU_GEN_FILE, LRU_TIER_MIN, LRU_TIER_MAX, + MAX_SWAPPINESS - swappiness, &pv); return positive_ctrl_err(&sp, &pv); } -- 2.53.0