linux-kernel - [PATCH 1/3] iov_iter: Lift memzero

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Date:   Tue,  9 Mar 2021 13:21:35 -0800
From:   ira.weiny@...el.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        David Sterba <dsterba@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] iov_iter: Lift memzero_page() to highmem.h

From: Ira Weiny <ira.weiny@...el.com>

memzero_page() can replace the kmap/memset/kunmap pattern in other
places in the code.  While zero_user() has the same interface it is not
the same call and its use should be limited and some of those calls may
be better converted from zero_user() to memzero_page().[1]  But that is
not addressed in this series.

Lift memzero_page() to highmem.

To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: David Sterba <dsterba@...e.com>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

[1] https://lore.kernel.org/lkml/CAHk-=wijdojzo56FzYqE5TOYw2Vws7ik3LEMGj9SPQaJJ+Z73Q@mail.gmail.com/
---
 include/linux/highmem.h | 7 +++++++
 lib/iov_iter.c          | 8 +-------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 44170f312ae7..832b49b50c7b 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -332,4 +332,11 @@ static inline void memcpy_to_page(struct page *page, size_t offset,
 	kunmap_local(to);
 }
 
+static inline void memzero_page(struct page *page, size_t offset, size_t len)
+{
+	char *addr = kmap_atomic(page);
+	memset(addr + offset, 0, len);
+	kunmap_atomic(addr);
+}
+
 #endif /* _LINUX_HIGHMEM_H */
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index f66c62aa7154..b0b1c8a01fae 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -5,6 +5,7 @@
 #include <linux/fault-inject-usercopy.h>
 #include <linux/uio.h>
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/splice.h>
@@ -464,13 +465,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 }
 EXPORT_SYMBOL(iov_iter_init);
 
-static void memzero_page(struct page *page, size_t offset, size_t len)
-{
-	char *addr = kmap_atomic(page);
-	memset(addr + offset, 0, len);
-	kunmap_atomic(addr);
-}
-
 static inline bool allocated(struct pipe_buffer *buf)
 {
 	return buf->ops == &default_pipe_buf_ops;
-- 
2.28.0.rc0.12.gb6a658bd00c9