[PATCH mm-unstable v1 4/5] mm/mglru: improve struct lru_gen_mm_walk

[Kinsey Ho]

Rename max_seq to seq in struct lru_gen_mm_walk to keep consistent with
struct lru_gen_mm_state. Note that seq is not always up to date with
max_seq from lru_gen_folio.

No functional changes.

Signed-off-by: Kinsey Ho <kinseyho@xxxxxxxxxx>
---
 include/linux/mmzone.h |  6 ++---
 mm/vmscan.c            | 50 ++++++++++++++++++++++--------------------
 2 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 22fd46c77840..e51c75270e82 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -468,7 +468,7 @@ enum {
 #define NR_BLOOM_FILTERS	2
 
 struct lru_gen_mm_state {
-	/* set to max_seq after each iteration */
+	/* synced with max_seq after each iteration */
 	unsigned long seq;
 	/* where the current iteration continues after */
 	struct list_head *head;
@@ -483,8 +483,8 @@ struct lru_gen_mm_state {
 struct lru_gen_mm_walk {
 	/* the lruvec under reclaim */
 	struct lruvec *lruvec;
-	/* unstable max_seq from lru_gen_folio */
-	unsigned long max_seq;
+	/* max_seq from lru_gen_folio: can be out of date */
+	unsigned long seq;
 	/* the next address within an mm to scan */
 	unsigned long next_addr;
 	/* to batch promoted pages */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8c77c332a67a..f1019afa7813 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2906,7 +2906,7 @@ static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last)
 
 	lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
 
-	hist = lru_hist_from_seq(walk->max_seq);
+	hist = lru_hist_from_seq(walk->seq);
 
 	for (i = 0; i < NR_MM_STATS; i++) {
 		WRITE_ONCE(mm_state->stats[hist][i],
@@ -2915,7 +2915,7 @@ static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last)
 	}
 
 	if (NR_HIST_GENS > 1 && last) {
-		hist = lru_hist_from_seq(walk->max_seq + 1);
+		hist = lru_hist_from_seq(walk->seq + 1);
 
 		for (i = 0; i < NR_MM_STATS; i++)
 			WRITE_ONCE(mm_state->stats[hist][i], 0);
@@ -2944,9 +2944,9 @@ static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **ite
 	 */
 	spin_lock(&mm_list->lock);
 
-	VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq);
+	VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->seq);
 
-	if (walk->max_seq <= mm_state->seq)
+	if (walk->seq <= mm_state->seq)
 		goto done;
 
 	if (!mm_state->head)
@@ -2976,7 +2976,7 @@ static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **ite
 	spin_unlock(&mm_list->lock);
 
 	if (mm && first)
-		reset_bloom_filter(mm_state, walk->max_seq + 1);
+		reset_bloom_filter(mm_state, walk->seq + 1);
 
 	if (*iter)
 		mmput_async(*iter);
@@ -2986,7 +2986,7 @@ static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **ite
 	return last;
 }
 
-static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
+static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long seq)
 {
 	bool success = false;
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
@@ -2995,9 +2995,9 @@ static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
 
 	spin_lock(&mm_list->lock);
 
-	VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq);
+	VM_WARN_ON_ONCE(mm_state->seq + 1 < seq);
 
-	if (max_seq > mm_state->seq) {
+	if (seq > mm_state->seq) {
 		mm_state->head = NULL;
 		mm_state->tail = NULL;
 		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
@@ -3348,7 +3348,8 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
 	struct lru_gen_mm_walk *walk = args->private;
 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
-	int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
+	DEFINE_MAX_SEQ(walk->lruvec);
+	int old_gen, new_gen = lru_gen_from_seq(max_seq);
 
 	pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl);
 	if (!pte)
@@ -3415,7 +3416,8 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
 	struct lru_gen_mm_walk *walk = args->private;
 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
-	int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
+	DEFINE_MAX_SEQ(walk->lruvec);
+	int old_gen, new_gen = lru_gen_from_seq(max_seq);
 
 	VM_WARN_ON_ONCE(pud_leaf(*pud));
 
@@ -3546,7 +3548,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
 		}
 
-		if (!walk->force_scan && !test_bloom_filter(mm_state, walk->max_seq, pmd + i))
+		if (!walk->force_scan && !test_bloom_filter(mm_state, walk->seq, pmd + i))
 			continue;
 
 		walk->mm_stats[MM_NONLEAF_FOUND]++;
@@ -3557,7 +3559,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 		walk->mm_stats[MM_NONLEAF_ADDED]++;
 
 		/* carry over to the next generation */
-		update_bloom_filter(mm_state, walk->max_seq + 1, pmd + i);
+		update_bloom_filter(mm_state, walk->seq + 1, pmd + i);
 	}
 
 	walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first);
@@ -3628,7 +3630,7 @@ static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
 		err = -EBUSY;
 
 		/* another thread might have called inc_max_seq() */
-		if (walk->max_seq != max_seq)
+		if (walk->seq != max_seq)
 			break;
 
 		/* folio_update_gen() requires stable folio_memcg() */
@@ -3765,7 +3767,7 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
 	return success;
 }
 
-static bool inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
+static bool inc_max_seq(struct lruvec *lruvec, unsigned long seq,
 			bool can_swap, bool force_scan)
 {
 	bool success;
@@ -3773,14 +3775,14 @@ static bool inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	int type, zone;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 restart:
-	if (max_seq < READ_ONCE(lrugen->max_seq))
+	if (seq < READ_ONCE(lrugen->max_seq))
 		return false;
 
 	spin_lock_irq(&lruvec->lru_lock);
 
 	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
 
-	success = max_seq == lrugen->max_seq;
+	success = seq == lrugen->max_seq;
 	if (!success)
 		goto unlock;
 
@@ -3833,7 +3835,7 @@ static bool inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	return success;
 }
 
-static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
+static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long seq,
 			       bool can_swap, bool force_scan)
 {
 	bool success;
@@ -3842,13 +3844,13 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
 
-	VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq));
+	VM_WARN_ON_ONCE(seq > READ_ONCE(lrugen->max_seq));
 
 	if (!mm_state)
-		return inc_max_seq(lruvec, max_seq, can_swap, force_scan);
+		return inc_max_seq(lruvec, seq, can_swap, force_scan);
 
 	/* see the comment in iterate_mm_list() */
-	if (max_seq <= READ_ONCE(mm_state->seq))
+	if (seq <= READ_ONCE(mm_state->seq))
 		return false;
 
 	/*
@@ -3858,18 +3860,18 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	 * is less efficient, but it avoids bursty page faults.
 	 */
 	if (!should_walk_mmu()) {
-		success = iterate_mm_list_nowalk(lruvec, max_seq);
+		success = iterate_mm_list_nowalk(lruvec, seq);
 		goto done;
 	}
 
 	walk = set_mm_walk(NULL, true);
 	if (!walk) {
-		success = iterate_mm_list_nowalk(lruvec, max_seq);
+		success = iterate_mm_list_nowalk(lruvec, seq);
 		goto done;
 	}
 
 	walk->lruvec = lruvec;
-	walk->max_seq = max_seq;
+	walk->seq = seq;
 	walk->can_swap = can_swap;
 	walk->force_scan = force_scan;
 
@@ -3880,7 +3882,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	} while (mm);
 done:
 	if (success) {
-		success = inc_max_seq(lruvec, max_seq, can_swap, force_scan);
+		success = inc_max_seq(lruvec, seq, can_swap, force_scan);
 		WARN_ON_ONCE(!success);
 	}
 
-- 
2.43.0.687.g38aa6559b0-goog