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* [PATCH 1/4] mm: Support THPs in zero_user_segments
@ 2020-11-24  4:15 Matthew Wilcox (Oracle)
  2020-11-24  4:15 ` [PATCH 2/4] fix mm-filemap-add-helper-for-finding-pages.patch Matthew Wilcox (Oracle)
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Matthew Wilcox (Oracle) @ 2020-11-24  4:15 UTC (permalink / raw)
  To: linux-mm, akpm; +Cc: Matthew Wilcox (Oracle)

We can only kmap() one subpage of a THP at a time, so loop over all
relevant subpages, skipping ones which don't need to be zeroed.  This is
too large to inline when THPs are enabled and we actually need highmem,
so put it in highmem.c.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/highmem.h | 19 ++++++++++---
 mm/highmem.c            | 59 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7d098bd621f6..f20916707ff9 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -193,13 +193,22 @@ static inline void clear_highpage(struct page *page)
 	kunmap_atomic(kaddr);
 }
 
+/*
+ * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
+ * If we pass in a head page, we can zero up to the size of the compound page.
+ */
+#if defined(CONFIG_HIGHMEM) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
+void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
+		unsigned start2, unsigned end2);
+#else /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
 static inline void zero_user_segments(struct page *page,
-	unsigned start1, unsigned end1,
-	unsigned start2, unsigned end2)
+		unsigned start1, unsigned end1,
+		unsigned start2, unsigned end2)
 {
 	void *kaddr = kmap_atomic(page);
+	unsigned int i;
 
-	BUG_ON(end1 > PAGE_SIZE || end2 > PAGE_SIZE);
+	BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 
 	if (end1 > start1)
 		memset(kaddr + start1, 0, end1 - start1);
@@ -208,8 +217,10 @@ static inline void zero_user_segments(struct page *page,
 		memset(kaddr + start2, 0, end2 - start2);
 
 	kunmap_atomic(kaddr);
-	flush_dcache_page(page);
+	for (i = 0; i < compound_nr(page); i++)
+		flush_dcache_page(page + i);
 }
+#endif /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
 
 static inline void zero_user_segment(struct page *page,
 	unsigned start, unsigned end)
diff --git a/mm/highmem.c b/mm/highmem.c
index 54bd233846c9..3e1087f2b735 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -359,6 +359,65 @@ void kunmap_high(struct page *page)
 		wake_up(pkmap_map_wait);
 }
 EXPORT_SYMBOL(kunmap_high);
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
+		unsigned start2, unsigned end2)
+{
+	unsigned int i;
+
+	BUG_ON(end1 > page_size(page) || end2 > page_size(page));
+
+	for (i = 0; i < compound_nr(page); i++) {
+		void *kaddr;
+		unsigned this_end;
+
+		if (end1 == 0 && start2 >= PAGE_SIZE) {
+			start2 -= PAGE_SIZE;
+			end2 -= PAGE_SIZE;
+			continue;
+		}
+
+		if (start1 >= PAGE_SIZE) {
+			start1 -= PAGE_SIZE;
+			end1 -= PAGE_SIZE;
+			if (start2) {
+				start2 -= PAGE_SIZE;
+				end2 -= PAGE_SIZE;
+			}
+			continue;
+		}
+
+		kaddr = kmap_atomic(page + i);
+
+		this_end = min_t(unsigned, end1, PAGE_SIZE);
+		if (end1 > start1)
+			memset(kaddr + start1, 0, this_end - start1);
+		end1 -= this_end;
+		start1 = 0;
+
+		if (start2 >= PAGE_SIZE) {
+			start2 -= PAGE_SIZE;
+			end2 -= PAGE_SIZE;
+		} else {
+			this_end = min_t(unsigned, end2, PAGE_SIZE);
+			if (end2 > start2)
+				memset(kaddr + start2, 0, this_end - start2);
+			end2 -= this_end;
+			start2 = 0;
+		}
+
+		kunmap_atomic(kaddr);
+		flush_dcache_page(page + i);
+
+		if (!end1 && !end2)
+			break;
+	}
+
+	BUG_ON((start1 | start2 | end1 | end2) != 0);
+}
+EXPORT_SYMBOL(zero_user_segments);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif /* CONFIG_HIGHMEM */
 
 #ifdef CONFIG_KMAP_LOCAL
-- 
2.29.2



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2020-11-24  4:15 [PATCH 1/4] mm: Support THPs in zero_user_segments Matthew Wilcox (Oracle)
2020-11-24  4:15 ` [PATCH 2/4] fix mm-filemap-add-helper-for-finding-pages.patch Matthew Wilcox (Oracle)
2020-11-24  4:15 ` [PATCH 3/4] fix mm-add-and-use-find_lock_entries.patch Matthew Wilcox (Oracle)
2020-11-24  4:15 ` [PATCH 4/4] fix mm-filemap-add-mapping_seek_hole_data.patch Matthew Wilcox (Oracle)

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