When using direct data placement the NIC writes some of the payload
directly to the destination buffer, and constructs the SKB such that it
points to this data. As a result, the skb_copy datagram_iter call will
attempt to copy data when it is not necessary.
Introduce new procedures for copy to iter/pages in case that the
source of the copy operation might be identical to the destination,
in such cases the copy is skipped only for bio_vec, later commits
uses those functions to introduce new skb copy(+hash) functions.
Signed-off-by: Boris Pismenny <bor...@mellanox.com>
Signed-off-by: Ben Ben-Ishay <benis...@mellanox.com>
Signed-off-by: Or Gerlitz <ogerl...@mellanox.com>
Signed-off-by: Yoray Zack <yor...@mellanox.com>
---
include/linux/uio.h | 12 ++++++++++++
lib/iov_iter.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 59 insertions(+)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 72d88566694e..3c42125a7f24 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -123,6 +123,7 @@ size_t copy_page_from_iter(struct page *page, size_t
offset, size_t bytes,
struct iov_iter *i);
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
+size_t _ddp_copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i);
size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
@@ -137,6 +138,15 @@ size_t copy_to_iter(const void *addr, size_t bytes, struct
iov_iter *i)
return _copy_to_iter(addr, bytes, i);
}
+static __always_inline __must_check
+size_t ddp_copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (unlikely(!check_copy_size(addr, bytes, true)))
+ return 0;
+ else
+ return _ddp_copy_to_iter(addr, bytes, i);
+}
+
static __always_inline __must_check
size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
@@ -265,6 +275,8 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes,
__wsum *csum, struct io
bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
struct iov_iter *i);
size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
struct iov_iter *i);
+size_t ddp_hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
+ struct iov_iter *i);
struct iovec *iovec_from_user(const struct iovec __user *uvector,
unsigned long nr_segs, unsigned long fast_segs,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index a21e6a5792c5..b8af1d3bbec0 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -473,6 +473,16 @@ static void memcpy_from_page(char *to, struct page *page,
size_t offset, size_t
kunmap_atomic(from);
}
+static void ddp_memcpy_to_page(struct page *page, size_t offset, const char
*from, size_t len)
+{
+ char *to = kmap_atomic(page);
+
+ if (to + offset != from)
+ memcpy(to + offset, from, len);
+
+ kunmap_atomic(to);
+}
+
static void memcpy_to_page(struct page *page, size_t offset, const char *from,
size_t len)
{
char *to = kmap_atomic(page);
@@ -625,6 +635,24 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr,
size_t bytes,
return bytes;
}
+size_t _ddp_copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+ const char *from = addr;
+ if (unlikely(iov_iter_is_pipe(i)))
+ return copy_pipe_to_iter(addr, bytes, i);
+ if (iter_is_iovec(i))
+ might_fault();
+ iterate_and_advance(i, bytes, v,
+ copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
+ ddp_memcpy_to_page(v.bv_page, v.bv_offset,
+ (from += v.bv_len) - v.bv_len, v.bv_len),
+ memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
+ )
+
+ return bytes;
+}
+EXPORT_SYMBOL(_ddp_copy_to_iter);
+
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
const char *from = addr;
@@ -1566,6 +1594,25 @@ size_t csum_and_copy_to_iter(const void *addr, size_t
bytes, void *csump,
}
EXPORT_SYMBOL(csum_and_copy_to_iter);
+size_t ddp_hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
+ struct iov_iter *i)
+{
+#ifdef CONFIG_CRYPTO_HASH
+ struct ahash_request *hash = hashp;
+ struct scatterlist sg;
+ size_t copied;
+
+ copied = ddp_copy_to_iter(addr, bytes, i);
+ sg_init_one(&sg, addr, copied);
+ ahash_request_set_crypt(hash, &sg, NULL, copied);
+ crypto_ahash_update(hash);
+ return copied;
+#else
+ return 0;
+#endif
+}
+EXPORT_SYMBOL(ddp_hash_and_copy_to_iter);
+
size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
struct iov_iter *i)
{
--
2.24.1
