[PATCH v2 2/3] use a nocache copy for bvecs and kvecs in copy_from_iter_nocache()

[Brian Boylston <brian.boylston@hpe.com>]

Update copy_from_iter_nocache() to use memcpy_nocache()
for bvecs and kvecs.

Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Brian Boylston <brian.boylston@hpe.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Reported-by: Oliver Moreno <oliver.moreno@hpe.com>
---
 lib/iov_iter.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7e3138c..71e4531 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -342,6 +342,13 @@ static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t
 	kunmap_atomic(from);
 }
 
+static void memcpy_from_page_nocache(char *to, struct page *page, size_t offset, size_t len)
+{
+	char *from = kmap_atomic(page);
+	memcpy_nocache(to, from + offset, len);
+	kunmap_atomic(from);
+}
+
 static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 {
 	char *to = kmap_atomic(page);
@@ -392,9 +399,10 @@ size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 	iterate_and_advance(i, bytes, v,
 		__copy_from_user_nocache((to += v.iov_len) - v.iov_len,
 					 v.iov_base, v.iov_len),
-		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
-				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy_from_page_nocache((to += v.bv_len) - v.bv_len,
+					 v.bv_page, v.bv_offset, v.bv_len),
+		memcpy_nocache((to += v.iov_len) - v.iov_len,
+			       v.iov_base, v.iov_len)
 	)
 
 	return bytes;
-- 
2.8.3