From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Let's add helpers to clear huge page segment(s). They provide the same
functionallity as zero_user_segment and zero_user, but for huge pages.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/mm.h | 7 +++++++
mm/memory.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 43 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c05d7cf..5e156fb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1797,6 +1797,13 @@ extern void dump_page(struct page *page);
extern void clear_huge_page(struct page *page,
unsigned long addr,
unsigned int pages_per_huge_page);
+extern void zero_huge_user_segment(struct page *page,
+ unsigned start, unsigned end);
+static inline void zero_huge_user(struct page *page,
+ unsigned start, unsigned len)
+{
+ zero_huge_user_segment(page, start, start + len);
+}
extern void copy_user_huge_page(struct page *dst, struct page *src,
unsigned long addr, struct vm_area_struct *vma,
unsigned int pages_per_huge_page);
diff --git a/mm/memory.c b/mm/memory.c
index f7a1fba..f02a8be 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4266,6 +4266,42 @@ void clear_huge_page(struct page *page,
}
}
+void zero_huge_user_segment(struct page *page, unsigned start, unsigned end)
+{
+ int i;
+ unsigned start_idx, end_idx;
+ unsigned start_off, end_off;
+
+ BUG_ON(end < start);
+
+ might_sleep();
+
+ if (start == end)
+ return;
+
+ start_idx = start >> PAGE_SHIFT;
+ start_off = start & ~PAGE_MASK;
+ end_idx = (end - 1) >> PAGE_SHIFT;
+ end_off = ((end - 1) & ~PAGE_MASK) + 1;
+
+ /*
+ * if start and end are on the same small page we can call
+ * zero_user_segment() once and save one kmap_atomic().
+ */
+ if (start_idx == end_idx)
+ return zero_user_segment(page + start_idx, start_off, end_off);
+
+ /* zero the first (possibly partial) page */
+ zero_user_segment(page + start_idx, start_off, PAGE_SIZE);
+ for (i = start_idx + 1; i < end_idx; i++) {
+ cond_resched();
+ clear_highpage(page + i);
+ flush_dcache_page(page + i);
+ }
+ /* zero the last (possibly partial) page */
+ zero_user_segment(page + end_idx, 0, end_off);
+}
+
static void copy_user_gigantic_page(struct page *dst, struct page *src,
unsigned long addr,
struct vm_area_struct *vma,
--
1.7.10.4
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