[RFC PATCH 3/9] mm/rmap: simplify rmap_walk invoke

[Huan Yang <link@vivo.com>]

Currently, the rmap walk is split into two functions: rmap_walk_locked
and rmap_walk, but their implementation functionality is very similar.

This patch simplifies the rmap walk function and moves the locked
parameter to rmap walk control.

No functional change.

Signed-off-by: Huan Yang <link@vivo.com>
---
 include/linux/rmap.h |  3 ++-
 mm/migrate.c         |  6 ++----
 mm/rmap.c            | 43 ++++++++++++++++---------------------------
 3 files changed, 20 insertions(+), 32 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 45904ff413ab..f0d17c971a20 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -996,6 +996,7 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, int flags);
  * arg: passed to rmap_one() and invalid_vma()
  * try_lock: bail out if the rmap lock is contended
  * contended: indicate the rmap traversal bailed out due to lock contention
+ * locked: already locked before invoke rmap_walk
  * rmap_one: executed on each vma where page is mapped
  * done: for checking traversing termination condition
  * anon_lock: for getting anon_lock by optimized way rather than default
@@ -1005,6 +1006,7 @@ struct rmap_walk_control {
 	void *arg;
 	bool try_lock;
 	bool contended;
+	bool locked;
 	/*
 	 * Return false if page table scanning in rmap_walk should be stopped.
 	 * Otherwise, return true.
@@ -1018,7 +1020,6 @@ struct rmap_walk_control {
 };
 
 void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
-void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
 struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
 					  struct rmap_walk_control *rwc);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 8cf0f9c9599d..a5a49af7857a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -355,15 +355,13 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, int flags)
 
 	struct rmap_walk_control rwc = {
 		.rmap_one = remove_migration_pte,
+		.locked = flags & RMP_LOCKED,
 		.arg = &rmap_walk_arg,
 	};
 
 	VM_BUG_ON_FOLIO((flags & RMP_USE_SHARED_ZEROPAGE) && (src != dst), src);
 
-	if (flags & RMP_LOCKED)
-		rmap_walk_locked(dst, &rwc);
-	else
-		rmap_walk(dst, &rwc);
+	rmap_walk(dst, &rwc);
 }
 
 /*
diff --git a/mm/rmap.c b/mm/rmap.c
index a312cae16bb5..bae9f79c7dc9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2253,14 +2253,12 @@ void try_to_unmap(struct folio *folio, enum ttu_flags flags)
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_unmap_one,
 		.arg = (void *)flags,
+		.locked = flags & TTU_RMAP_LOCKED,
 		.done = folio_not_mapped,
 		.anon_lock = folio_lock_anon_vma_read,
 	};
 
-	if (flags & TTU_RMAP_LOCKED)
-		rmap_walk_locked(folio, &rwc);
-	else
-		rmap_walk(folio, &rwc);
+	rmap_walk(folio, &rwc);
 }
 
 /*
@@ -2581,6 +2579,7 @@ void try_to_migrate(struct folio *folio, enum ttu_flags flags)
 		.rmap_one = try_to_migrate_one,
 		.arg = (void *)flags,
 		.done = folio_not_mapped,
+		.locked = flags & TTU_RMAP_LOCKED,
 		.anon_lock = folio_lock_anon_vma_read,
 	};
 
@@ -2607,10 +2606,7 @@ void try_to_migrate(struct folio *folio, enum ttu_flags flags)
 	if (!folio_test_ksm(folio) && folio_test_anon(folio))
 		rwc.invalid_vma = invalid_migration_vma;
 
-	if (flags & TTU_RMAP_LOCKED)
-		rmap_walk_locked(folio, &rwc);
-	else
-		rmap_walk(folio, &rwc);
+	rmap_walk(folio, &rwc);
 }
 
 #ifdef CONFIG_DEVICE_PRIVATE
@@ -2795,17 +2791,16 @@ static struct anon_vma *rmap_walk_anon_lock(const struct folio *folio,
  * rmap method
  * @folio: the folio to be handled
  * @rwc: control variable according to each walk type
- * @locked: caller holds relevant rmap lock
  *
  * Find all the mappings of a folio using the mapping pointer and the vma
  * chains contained in the anon_vma struct it points to.
  */
-static void rmap_walk_anon(struct folio *folio,
-		struct rmap_walk_control *rwc, bool locked)
+static void rmap_walk_anon(struct folio *folio, struct rmap_walk_control *rwc)
 {
 	struct anon_vma *anon_vma;
 	pgoff_t pgoff_start, pgoff_end;
 	struct anon_vma_chain *avc;
+	bool locked = rwc->locked;
 
 	if (locked) {
 		anon_vma = folio_anon_vma(folio);
@@ -2908,14 +2903,14 @@ static void __rmap_walk_file(struct folio *folio, struct address_space *mapping,
  * rmap_walk_file - do something to file page using the object-based rmap method
  * @folio: the folio to be handled
  * @rwc: control variable according to each walk type
- * @locked: caller holds relevant rmap lock
  *
  * Find all the mappings of a folio using the mapping pointer and the vma chains
  * contained in the address_space struct it points to.
  */
-static void rmap_walk_file(struct folio *folio,
-		struct rmap_walk_control *rwc, bool locked)
+static void rmap_walk_file(struct folio *folio, struct rmap_walk_control *rwc)
 {
+	bool locked = rwc->locked;
+
 	/*
 	 * The folio lock not only makes sure that folio->mapping cannot
 	 * suddenly be NULLified by truncation, it makes sure that the structure
@@ -2933,23 +2928,17 @@ static void rmap_walk_file(struct folio *folio,
 
 void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
 {
+	/* no ksm support for now if locked */
+	VM_BUG_ON_FOLIO(rwc->locked && folio_test_ksm(folio), folio);
+	/* if already locked, why try lock again? */
+	VM_BUG_ON(rwc->locked && rwc->try_lock);
+
 	if (unlikely(folio_test_ksm(folio)))
 		rmap_walk_ksm(folio, rwc);
 	else if (folio_test_anon(folio))
-		rmap_walk_anon(folio, rwc, false);
-	else
-		rmap_walk_file(folio, rwc, false);
-}
-
-/* Like rmap_walk, but caller holds relevant rmap lock */
-void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
-{
-	/* no ksm support for now */
-	VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
-	if (folio_test_anon(folio))
-		rmap_walk_anon(folio, rwc, true);
+		rmap_walk_anon(folio, rwc);
 	else
-		rmap_walk_file(folio, rwc, true);
+		rmap_walk_file(folio, rwc);
 }
 
 #ifdef CONFIG_HUGETLB_PAGE
-- 
2.34.1