linux-kernel - [PATCH v2 13/25] fs: Add zero_user

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Date:   Tue, 11 Feb 2020 20:18:33 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 13/25] fs: Add zero_user_large

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

We can't kmap() a THP, so add a wrapper around zero_user() for large
pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/highmem.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ea5cdbd8c2c3..4465b8784353 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -245,6 +245,28 @@ static inline void zero_user(struct page *page,
 	zero_user_segments(page, start, start + size, 0, 0);
 }
 
+static inline void zero_user_large(struct page *page,
+		unsigned start, unsigned size)
+{
+	unsigned int i;
+
+	for (i = 0; i < thp_order(page); i++) {
+		if (start > PAGE_SIZE) {
+			start -= PAGE_SIZE;
+		} else {
+			unsigned this_size = size;
+
+			if (size > (PAGE_SIZE - start))
+				this_size = PAGE_SIZE - start;
+			zero_user(page + i, start, this_size);
+			start = 0;
+			size -= this_size;
+			if (!size)
+				break;
+		}
+	}
+}
+
 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
 
 static inline void copy_user_highpage(struct page *to, struct page *from,
-- 
2.25.0