[PATCH v2 4/7] mm: Mass constification of folio/page pointers

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Now that page_pgoff() takes const pointers, we can constify the
pointers to a lot of functions.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/ksm.h  |  7 ++++---
 include/linux/rmap.h | 10 +++++-----
 mm/internal.h        |  5 +++--
 mm/ksm.c             |  5 +++--
 mm/memory-failure.c  | 24 +++++++++++++-----------
 mm/page_vma_mapped.c |  5 +++--
 mm/rmap.c            | 11 ++++++-----
 7 files changed, 37 insertions(+), 30 deletions(-)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 11690dacd986..c4a8891f6e7d 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -92,7 +92,7 @@ struct folio *ksm_might_need_to_copy(struct folio *folio,
 
 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
-void collect_procs_ksm(struct folio *folio, struct page *page,
+void collect_procs_ksm(const struct folio *folio, const struct page *page,
 		struct list_head *to_kill, int force_early);
 long ksm_process_profit(struct mm_struct *);
 
@@ -125,8 +125,9 @@ static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
 {
 }
 
-static inline void collect_procs_ksm(struct folio *folio, struct page *page,
-				     struct list_head *to_kill, int force_early)
+static inline void collect_procs_ksm(const struct folio *folio,
+		const struct page *page, struct list_head *to_kill,
+		int force_early)
 {
 }
 
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 78923015a2e8..683a04088f3f 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -171,7 +171,7 @@ static inline void anon_vma_merge(struct vm_area_struct *vma,
 	unlink_anon_vmas(next);
 }
 
-struct anon_vma *folio_get_anon_vma(struct folio *folio);
+struct anon_vma *folio_get_anon_vma(const struct folio *folio);
 
 /* RMAP flags, currently only relevant for some anon rmap operations. */
 typedef int __bitwise rmap_t;
@@ -194,8 +194,8 @@ enum rmap_level {
 	RMAP_LEVEL_PMD,
 };
 
-static inline void __folio_rmap_sanity_checks(struct folio *folio,
-		struct page *page, int nr_pages, enum rmap_level level)
+static inline void __folio_rmap_sanity_checks(const struct folio *folio,
+		const struct page *page, int nr_pages, enum rmap_level level)
 {
 	/* hugetlb folios are handled separately. */
 	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
@@ -771,14 +771,14 @@ struct rmap_walk_control {
 	bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma,
 					unsigned long addr, void *arg);
 	int (*done)(struct folio *folio);
-	struct anon_vma *(*anon_lock)(struct folio *folio,
+	struct anon_vma *(*anon_lock)(const struct folio *folio,
 				      struct rmap_walk_control *rwc);
 	bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
 };
 
 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(struct folio *folio,
+struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
 					  struct rmap_walk_control *rwc);
 
 #else	/* !CONFIG_MMU */
diff --git a/mm/internal.h b/mm/internal.h
index fffa9df41495..71a30e779223 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1072,10 +1072,11 @@ void ClearPageHWPoisonTakenOff(struct page *page);
 bool take_page_off_buddy(struct page *page);
 bool put_page_back_buddy(struct page *page);
 struct task_struct *task_early_kill(struct task_struct *tsk, int force_early);
-void add_to_kill_ksm(struct task_struct *tsk, struct page *p,
+void add_to_kill_ksm(struct task_struct *tsk, const struct page *p,
 		     struct vm_area_struct *vma, struct list_head *to_kill,
 		     unsigned long ksm_addr);
-unsigned long page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
+unsigned long page_mapped_in_vma(const struct page *page,
+		struct vm_area_struct *vma);
 
 #else
 static inline void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
diff --git a/mm/ksm.c b/mm/ksm.c
index 2bbb321f92ac..1fed2e3e01e0 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1052,7 +1052,8 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma,
 	return err;
 }
 
-static inline struct ksm_stable_node *folio_stable_node(struct folio *folio)
+static inline
+struct ksm_stable_node *folio_stable_node(const struct folio *folio)
 {
 	return folio_test_ksm(folio) ? folio_raw_mapping(folio) : NULL;
 }
@@ -3066,7 +3067,7 @@ void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc)
 /*
  * Collect processes when the error hit an ksm page.
  */
-void collect_procs_ksm(struct folio *folio, struct page *page,
+void collect_procs_ksm(const struct folio *folio, const struct page *page,
 		struct list_head *to_kill, int force_early)
 {
 	struct ksm_stable_node *stable_node;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index ea9d883c01c1..7ce7ba8586f5 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -445,7 +445,7 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
  * Schedule a process for later kill.
  * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
  */
-static void __add_to_kill(struct task_struct *tsk, struct page *p,
+static void __add_to_kill(struct task_struct *tsk, const struct page *p,
 			  struct vm_area_struct *vma, struct list_head *to_kill,
 			  unsigned long addr)
 {
@@ -461,7 +461,7 @@ static void __add_to_kill(struct task_struct *tsk, struct page *p,
 	if (is_zone_device_page(p))
 		tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
 	else
-		tk->size_shift = page_shift(compound_head(p));
+		tk->size_shift = folio_shift(page_folio(p));
 
 	/*
 	 * Send SIGKILL if "tk->addr == -EFAULT". Also, as
@@ -486,7 +486,7 @@ static void __add_to_kill(struct task_struct *tsk, struct page *p,
 	list_add_tail(&tk->nd, to_kill);
 }
 
-static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
+static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
 		struct vm_area_struct *vma, struct list_head *to_kill,
 		unsigned long addr)
 {
@@ -509,7 +509,7 @@ static bool task_in_to_kill_list(struct list_head *to_kill,
 	return false;
 }
 
-void add_to_kill_ksm(struct task_struct *tsk, struct page *p,
+void add_to_kill_ksm(struct task_struct *tsk, const struct page *p,
 		     struct vm_area_struct *vma, struct list_head *to_kill,
 		     unsigned long addr)
 {
@@ -606,8 +606,9 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
 /*
  * Collect processes when the error hit an anonymous page.
  */
-static void collect_procs_anon(struct folio *folio, struct page *page,
-		struct list_head *to_kill, int force_early)
+static void collect_procs_anon(const struct folio *folio,
+		const struct page *page, struct list_head *to_kill,
+		int force_early)
 {
 	struct task_struct *tsk;
 	struct anon_vma *av;
@@ -643,8 +644,9 @@ static void collect_procs_anon(struct folio *folio, struct page *page,
 /*
  * Collect processes when the error hit a file mapped page.
  */
-static void collect_procs_file(struct folio *folio, struct page *page,
-		struct list_head *to_kill, int force_early)
+static void collect_procs_file(const struct folio *folio,
+		const struct page *page, struct list_head *to_kill,
+		int force_early)
 {
 	struct vm_area_struct *vma;
 	struct task_struct *tsk;
@@ -680,7 +682,7 @@ static void collect_procs_file(struct folio *folio, struct page *page,
 }
 
 #ifdef CONFIG_FS_DAX
-static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p,
+static void add_to_kill_fsdax(struct task_struct *tsk, const struct page *p,
 			      struct vm_area_struct *vma,
 			      struct list_head *to_kill, pgoff_t pgoff)
 {
@@ -691,7 +693,7 @@ static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p,
 /*
  * Collect processes when the error hit a fsdax page.
  */
-static void collect_procs_fsdax(struct page *page,
+static void collect_procs_fsdax(const struct page *page,
 		struct address_space *mapping, pgoff_t pgoff,
 		struct list_head *to_kill, bool pre_remove)
 {
@@ -725,7 +727,7 @@ static void collect_procs_fsdax(struct page *page,
 /*
  * Collect the processes who have the corrupted page mapped to kill.
  */
-static void collect_procs(struct folio *folio, struct page *page,
+static void collect_procs(const struct folio *folio, const struct page *page,
 		struct list_head *tokill, int force_early)
 {
 	if (!folio->mapping)
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index ade3c6833587..82e20dbbedb7 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -325,9 +325,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
  * outside the VMA or not present, returns -EFAULT.
  * Only valid for normal file or anonymous VMAs.
  */
-unsigned long page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
+unsigned long page_mapped_in_vma(const struct page *page,
+		struct vm_area_struct *vma)
 {
-	struct folio *folio = page_folio(page);
+	const struct folio *folio = page_folio(page);
 	struct page_vma_mapped_walk pvmw = {
 		.pfn = page_to_pfn(page),
 		.nr_pages = 1,
diff --git a/mm/rmap.c b/mm/rmap.c
index a7b4f9ba9a14..2c561b1e52cc 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -497,7 +497,7 @@ void __init anon_vma_init(void)
  * concurrently without folio lock protection). See folio_lock_anon_vma_read()
  * which has already covered that, and comment above remap_pages().
  */
-struct anon_vma *folio_get_anon_vma(struct folio *folio)
+struct anon_vma *folio_get_anon_vma(const struct folio *folio)
 {
 	struct anon_vma *anon_vma = NULL;
 	unsigned long anon_mapping;
@@ -541,7 +541,7 @@ struct anon_vma *folio_get_anon_vma(struct folio *folio)
  * reference like with folio_get_anon_vma() and then block on the mutex
  * on !rwc->try_lock case.
  */
-struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
+struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
 					  struct rmap_walk_control *rwc)
 {
 	struct anon_vma *anon_vma = NULL;
@@ -1275,8 +1275,9 @@ static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
  * @vma:	the vm area in which the mapping is added
  * @address:	the user virtual address mapped
  */
-static void __page_check_anon_rmap(struct folio *folio, struct page *page,
-	struct vm_area_struct *vma, unsigned long address)
+static void __page_check_anon_rmap(const struct folio *folio,
+		const struct page *page, struct vm_area_struct *vma,
+		unsigned long address)
 {
 	/*
 	 * The page's anon-rmap details (mapping and index) are guaranteed to
@@ -2573,7 +2574,7 @@ void __put_anon_vma(struct anon_vma *anon_vma)
 		anon_vma_free(root);
 }
 
-static struct anon_vma *rmap_walk_anon_lock(struct folio *folio,
+static struct anon_vma *rmap_walk_anon_lock(const struct folio *folio,
 					    struct rmap_walk_control *rwc)
 {
 	struct anon_vma *anon_vma;
-- 
2.43.0