[PATCH v4 3/9] mm: move anon-exclusive batch helper to rmap.h

[Dev Jain <dev.jain@arm.com>]

In preparation for optimizing large folio unmapping, we need to reuse
the page_anon_exclusive_batch helper in rmap.c and rmap.h and obey the
existing use in mprotect.c .

Therefore, move it from mprotect.c to rmap.h.

While at it, change return type, start_idx and max_len to unsigned long
type for future proofing against THP support at >= PUD level. Also
make the helper return the anon-exclusivity state via a pointer parameter.

Shorten 'expected_anon_exclusive' to exclusive for brevity.

Reviewed-by: Barry Song <baohua@kernel.org>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
 include/linux/rmap.h | 18 ++++++++++++++++++
 mm/mprotect.c        | 25 ++++---------------------
 2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 74cca0e3c7264..43d6bbecd2fab 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -106,6 +106,24 @@ enum ttu_flags {
 
 #ifdef CONFIG_MMU
 
+/*
+ * Get max length of consecutive PTEs pointing to PageAnonExclusive() pages or
+ * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce
+ * that the PTEs point to consecutive pages of the same anon large folio.
+ */
+static __always_inline unsigned long page_anon_exclusive_batch(unsigned long start_idx,
+		unsigned long max_len, struct page *first_page, bool *exclusive)
+{
+	unsigned long idx;
+
+	*exclusive = PageAnonExclusive(first_page + start_idx);
+	for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) {
+		if (*exclusive != PageAnonExclusive(first_page + idx))
+			break;
+	}
+	return idx - start_idx;
+}
+
 void anon_vma_init(void);	/* create anon_vma_cachep */
 
 #ifdef CONFIG_MM_ID
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ef4e7188e24da..0048a2406ed34 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -30,6 +30,7 @@
 #include <linux/mm_inline.h>
 #include <linux/pgtable.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/rmap.h>
 #include <uapi/linux/mman.h>
 #include <asm/cacheflush.h>
 #include <asm/mmu_context.h>
@@ -138,23 +139,6 @@ static __always_inline void prot_commit_flush_ptes(struct vm_area_struct *vma,
 		tlb_flush_pte_range(tlb, addr, nr_ptes * PAGE_SIZE);
 }
 
-/*
- * Get max length of consecutive ptes pointing to PageAnonExclusive() pages or
- * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce
- * that the ptes point to consecutive pages of the same anon large folio.
- */
-static __always_inline int page_anon_exclusive_batch(int start_idx, int max_len,
-		struct page *first_page, bool expected_anon_exclusive)
-{
-	int idx;
-
-	for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) {
-		if (expected_anon_exclusive != PageAnonExclusive(first_page + idx))
-			break;
-	}
-	return idx - start_idx;
-}
-
 /*
  * This function is a result of trying our very best to retain the
  * "avoid the write-fault handler" optimization. In can_change_pte_writable(),
@@ -173,16 +157,15 @@ static __always_inline void commit_anon_folio_batch(struct vm_area_struct *vma,
 		struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep,
 		pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb)
 {
-	bool expected_anon_exclusive;
+	bool exclusive;
 	int batch_idx = 0;
 	int len;
 
 	while (nr_ptes) {
-		expected_anon_exclusive = PageAnonExclusive(first_page + batch_idx);
 		len = page_anon_exclusive_batch(batch_idx, nr_ptes,
-					first_page, expected_anon_exclusive);
+					first_page, &exclusive);
 		prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, len,
-				       batch_idx, expected_anon_exclusive, tlb);
+				       batch_idx, exclusive, tlb);
 		batch_idx += len;
 		nr_ptes -= len;
 	}
-- 
2.43.0