[RFC PATCH 11/12] mm: rename non_swap_entry() to is_non_present_entry()

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Referring to non-swap swap entries is simply confusing. While we store
non-present entries unrelated to swap itself, in swp_entry_t fields, we can
avoid referring to them as 'non-swap' entries.

Instead, refer to them as non-present entries, as opposed to strictly swap
entries. We achieve this by renaming non_swap_entry() to
is_non_present_entry(), which also adds an 'is_' prefix for consistency
with other similar predicate functions.

Also update comments accordingly.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 arch/s390/mm/gmap_helpers.c |  2 +-
 arch/s390/mm/pgtable.c      |  2 +-
 fs/proc/task_mmu.c          |  2 +-
 include/linux/swapops.h     | 21 ++++++++++++++++-----
 mm/filemap.c                |  2 +-
 mm/hmm.c                    |  2 +-
 mm/madvise.c                |  4 ++--
 mm/memory.c                 |  8 ++++----
 mm/mincore.c                |  2 +-
 mm/userfaultfd.c            |  2 +-
 10 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/arch/s390/mm/gmap_helpers.c b/arch/s390/mm/gmap_helpers.c
index d4c3c36855e2..2c41276a34c5 100644
--- a/arch/s390/mm/gmap_helpers.c
+++ b/arch/s390/mm/gmap_helpers.c
@@ -28,7 +28,7 @@
  */
 static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry)
 {
-	if (!non_swap_entry(entry))
+	if (!is_non_present_entry(entry))
 		dec_mm_counter(mm, MM_SWAPENTS);
 	else if (is_migration_entry(entry))
 		dec_mm_counter(mm, mm_counter(pfn_swap_entry_folio(entry)));
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 0fde20bbc50b..0c795f3c324f 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -685,7 +685,7 @@ void ptep_unshadow_pte(struct mm_struct *mm, unsigned long saddr, pte_t *ptep)
 
 static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry)
 {
-	if (!non_swap_entry(entry))
+	if (!is_non_present_entry(entry))
 		dec_mm_counter(mm, MM_SWAPENTS);
 	else if (is_migration_entry(entry)) {
 		struct folio *folio = pfn_swap_entry_folio(entry);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1c32a0e2b965..28f30e01e504 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1022,7 +1022,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 	} else {
 		swp_entry_t swpent = pte_to_swp_entry(ptent);
 
-		if (!non_swap_entry(swpent)) {
+		if (!is_non_present_entry(swpent)) {
 			int mapcount;
 
 			mss->swap += PAGE_SIZE;
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 8642e590504a..fb463d75fa90 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -645,7 +645,18 @@ static inline int is_pmd_device_private_entry(pmd_t pmd)
 
 #endif /* CONFIG_ZONE_DEVICE && CONFIG_ARCH_ENABLE_THP_MIGRATION */
 
-static inline int non_swap_entry(swp_entry_t entry)
+/**
+ * is_non_present_entry() - Determine if this is a miscellaneous
+ * non-present entry.
+ * @entry: The entry to examine.
+ *
+ * This function determines whether data encoded in non-present leaf page
+ * tables is a migration entry, device private entry, marker entry, etc. -
+ * that is a non-present entry that is not a swap entry.
+ *
+ * Returns: true if is a non-present entry, otherwise false.
+ */
+static inline bool is_non_present_entry(swp_entry_t entry)
 {
 	return swp_type(entry) >= MAX_SWAPFILES;
 }
@@ -661,9 +672,9 @@ static inline int is_pmd_non_present_folio_entry(pmd_t pmd)
  * @entryp: Output pointer to a swap entry that will be populated upon
  * success.
  *
- * Determines if the PTE describes an entry in swap or swap cache (i.e. is a
- * swap entry and not a non-swap entry), if so it sets @entryp to the swap
- * entry.
+ * Determines if the PTE describes an entry in swap or swap cache (i.e. is
+ * a swap entry and not a non-present entry), if so it sets @entryp to the
+ * swap entry.
  *
  * This should only be used if we do not have any prior knowledge of this
  * PTE's state.
@@ -678,7 +689,7 @@ static inline bool get_pte_swap_entry(pte_t pte, swp_entry_t *entryp)
 		return false;
 
 	*entryp = pte_to_swp_entry(pte);
-	if (non_swap_entry(*entryp))
+	if (is_non_present_entry(*entryp))
 		return false;
 
 	return true;
diff --git a/mm/filemap.c b/mm/filemap.c
index 893ba49808b7..1440e176e124 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -4553,7 +4553,7 @@ static void filemap_cachestat(struct address_space *mapping,
 				swp_entry_t swp = radix_to_swp_entry(folio);
 
 				/* swapin error results in poisoned entry */
-				if (non_swap_entry(swp))
+				if (is_non_present_entry(swp))
 					goto resched;
 
 				/*
diff --git a/mm/hmm.c b/mm/hmm.c
index a56081d67ad6..66e18b28a21d 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -274,7 +274,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 		if (!required_fault)
 			goto out;
 
-		if (!non_swap_entry(entry))
+		if (!is_non_present_entry(entry))
 			goto fault;
 
 		if (is_device_private_entry(entry))
diff --git a/mm/madvise.c b/mm/madvise.c
index 578036ef6675..a259dae2b899 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -248,7 +248,7 @@ static void shmem_swapin_range(struct vm_area_struct *vma,
 			continue;
 		entry = radix_to_swp_entry(folio);
 		/* There might be swapin error entries in shmem mapping. */
-		if (non_swap_entry(entry))
+		if (is_non_present_entry(entry))
 			continue;
 
 		addr = vma->vm_start +
@@ -690,7 +690,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 			swp_entry_t entry;
 
 			entry = pte_to_swp_entry(ptent);
-			if (!non_swap_entry(entry)) {
+			if (!is_non_present_entry(entry)) {
 				max_nr = (end - addr) / PAGE_SIZE;
 				nr = swap_pte_batch(pte, max_nr, ptent);
 				nr_swap -= nr;
diff --git a/mm/memory.c b/mm/memory.c
index cc163060933f..8968ba0b076f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -847,7 +847,7 @@ struct page *vm_normal_page_pud(struct vm_area_struct *vma,
  * @ptep: pte pointer into the locked page table mapping the folio page
  * @orig_pte: pte value at @ptep
  *
- * Restore a device-exclusive non-swap entry to an ordinary present pte.
+ * Restore a device-exclusive non-present entry to an ordinary present pte.
  *
  * The folio and the page table must be locked, and MMU notifiers must have
  * been called to invalidate any (exclusive) device mappings.
@@ -931,7 +931,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 	struct page *page;
 	swp_entry_t entry = pte_to_swp_entry(orig_pte);
 
-	if (likely(!non_swap_entry(entry))) {
+	if (likely(!is_non_present_entry(entry))) {
 		if (swap_duplicate(entry) < 0)
 			return -EIO;
 
@@ -1739,7 +1739,7 @@ static inline int zap_nonpresent_ptes(struct mmu_gather *tlb,
 		rss[mm_counter(folio)]--;
 		folio_remove_rmap_pte(folio, page, vma);
 		folio_put(folio);
-	} else if (!non_swap_entry(entry)) {
+	} else if (!is_non_present_entry(entry)) {
 		/* Genuine swap entries, hence a private anon pages */
 		if (!should_zap_cows(details))
 			return 1;
@@ -4646,7 +4646,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		goto out;
 
 	entry = pte_to_swp_entry(vmf->orig_pte);
-	if (unlikely(non_swap_entry(entry))) {
+	if (unlikely(is_non_present_entry(entry))) {
 		if (is_migration_entry(entry)) {
 			migration_entry_wait(vma->vm_mm, vmf->pmd,
 					     vmf->address);
diff --git a/mm/mincore.c b/mm/mincore.c
index 8ec4719370e1..61531a7cd8b0 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -63,7 +63,7 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)
 	 * absent. Page table may contain migration or hwpoison
 	 * entries which are always uptodate.
 	 */
-	if (non_swap_entry(entry))
+	if (is_non_present_entry(entry))
 		return !shmem;
 
 	/*
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 00122f42718c..04fab82a1119 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1427,7 +1427,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd
 		struct folio *folio = NULL;
 
 		entry = pte_to_swp_entry(orig_src_pte);
-		if (non_swap_entry(entry)) {
+		if (is_non_present_entry(entry)) {
 			if (is_migration_entry(entry)) {
 				pte_unmap(src_pte);
 				pte_unmap(dst_pte);
-- 
2.51.0