[RFC PATCH 2/2] mm: add zero_user_folio_segments()

[Yin Fengwei <fengwei.yin@intel.com>]

zero_user_folio_segments() has same function as zero_user_segments().
but take folio as parameter. Update folio_zero_segments(),
folio_zero_segment() and folio_zero_range() to use it.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
---
 include/linux/highmem.h | 26 +++++++++++++++++---
 mm/highmem.c            | 53 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index b06254e76d99..0039116e416a 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -266,6 +266,8 @@ static inline void tag_clear_highpage(struct page *page)
 #ifdef CONFIG_HIGHMEM
 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 		unsigned start2, unsigned end2);
+void zero_user_folio_segments(struct folio *folio, unsigned start1,
+		unsigned end1, unsigned start2, unsigned end2);
 #else
 static inline void zero_user_segments(struct page *page,
 		unsigned start1, unsigned end1,
@@ -286,6 +288,24 @@ static inline void zero_user_segments(struct page *page,
 	for (i = 0; i < compound_nr(page); i++)
 		flush_dcache_page(page + i);
 }
+
+static inline void zero_user_folio_segments(struct folio *folio,
+		unsigned start1, unsigned end1,
+		unsigned start2, unsigned end2)
+{
+	void *kaddr = kmap_local_page(&folio->page);
+
+	BUG_ON(end1 > folio_size(folio) || end2 > folio_size(folio));
+
+	if (end1 > start1)
+		memset(kaddr + start1, 0, end1 - start1);
+
+	if (end2 > start2)
+		memset(kaddr + start2, 0, end2 - start2);
+
+	kunmap_local(kaddr);
+	flush_dcache_folio(folio);
+}
 #endif
 
 static inline void zero_user_segment(struct page *page,
@@ -454,7 +474,7 @@ static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
 static inline void folio_zero_segments(struct folio *folio,
 		size_t start1, size_t xend1, size_t start2, size_t xend2)
 {
-	zero_user_segments(&folio->page, start1, xend1, start2, xend2);
+	zero_user_folio_segments(folio, start1, xend1, start2, xend2);
 }
 
 /**
@@ -466,7 +486,7 @@ static inline void folio_zero_segments(struct folio *folio,
 static inline void folio_zero_segment(struct folio *folio,
 		size_t start, size_t xend)
 {
-	zero_user_segments(&folio->page, start, xend, 0, 0);
+	zero_user_folio_segments(folio, start, xend, 0, 0);
 }
 
 /**
@@ -478,7 +498,7 @@ static inline void folio_zero_segment(struct folio *folio,
 static inline void folio_zero_range(struct folio *folio,
 		size_t start, size_t length)
 {
-	zero_user_segments(&folio->page, start, start + length, 0, 0);
+	zero_user_folio_segments(folio, start, start + length, 0, 0);
 }
 
 #endif /* _LINUX_HIGHMEM_H */
diff --git a/mm/highmem.c b/mm/highmem.c
index db251e77f98f..e234b249208f 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -443,6 +443,59 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 	BUG_ON((start1 | start2 | end1 | end2) != 0);
 }
 EXPORT_SYMBOL(zero_user_segments);
+
+static inline void zero_user_folio_segment(struct folio *folio,
+		unsigned start1, unsigned end1,
+		unsigned start2, unsigned end2)
+{
+	void *kaddr;
+	unsigned s;
+
+	BUG_ON(end1 > folio_size(folio) || end2 > folio_size(folio));
+
+	if (start1 > start2) {
+		swap(start1, start2);
+		swap(end1, end2);
+	}
+
+	if (start1 >= end1)
+		start1 = end1 = 0;
+
+	if (start2 >= end2)
+		start2 = end2 = 0;
+
+	start2 = max_t(unsigned, end1, start2);
+	s = start1;
+	while((start1 < end1) || (start2 < end2)) {
+		kaddr = kmap_local_folio(folio,
+				offset_in_folio(folio, PAGE_ALIGN_DOWN(s)));
+
+		if ((end2 > start2) && (end1 >= start1)) {
+			unsigned this_end = min_t(unsigned, end2,
+					PAGE_ALIGN_DOWN(start2) + PAGE_SIZE);
+
+			memset(kaddr + offset_in_page(start2), 0,
+						this_end - start2);
+
+			start2 = this_end;
+		}
+
+		if (end1 > start1) {
+			unsigned this_end = min_t(unsigned, end1,
+					PAGE_ALIGN_DOWN(start1) + PAGE_SIZE);
+
+			memset(kaddr + offset_in_page(start1), 0,
+							this_end - start1);
+			s = start1 = this_end;
+		} else {
+			s = start2;
+		}
+		kunmap_local(kaddr);
+	}
+
+	flush_dcache_folio(folio);
+}
+EXPORT_SYMBOL(zero_user_folio_segments);
 #endif /* CONFIG_HIGHMEM */
 
 #ifdef CONFIG_KMAP_LOCAL
-- 
2.30.2