[rds-devel] [PATCH RFC net-next 6/6] rds: zerocopy Tx support.
Sowmini Varadhan
sowmini.varadhan at oracle.com
Wed Jan 17 04:20:04 PST 2018
If the MSG_ZEROCOPY flag is specified with rds_sendmsg(), and,
if the SO_ZEROCOPY socket option has been set on the PF_RDS socket,
application pages sent down with rds_sendmsg() are pinned.
The pinning uses the accounting infrastructure added by
Commit a91dbff551a6 ("sock: ulimit on MSG_ZEROCOPY pages")
The payload bytes in the message may not be modified for the
duration that the message has been pinned. A multi-threaded
application using this infrastructure may thus need to be notified
about send-completion so that it can free/reuse the buffers
passed to rds_sendmsg(). Notification of send-completion will
identify each message-buffer by a cookie that the application
must specify as ancillary data to rds_sendmsg().
The ancillary data in this case has cmsg_level == SOL_RDS
and cmsg_type == RDS_CMSG_ZCOPY_COOKIE.
Signed-off-by: Sowmini Varadhan <sowmini.varadhan at oracle.com>
---
include/uapi/linux/rds.h | 1 +
net/rds/message.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
net/rds/rds.h | 3 ++-
net/rds/send.c | 27 ++++++++++++++++++++++++---
4 files changed, 70 insertions(+), 5 deletions(-)
diff --git a/include/uapi/linux/rds.h b/include/uapi/linux/rds.h
index e71d449..09b8cc6 100644
--- a/include/uapi/linux/rds.h
+++ b/include/uapi/linux/rds.h
@@ -102,6 +102,7 @@
#define RDS_CMSG_ATOMIC_CSWP 7
#define RDS_CMSG_MASKED_ATOMIC_FADD 8
#define RDS_CMSG_MASKED_ATOMIC_CSWP 9
+#define RDS_CMSG_ZCOPY_COOKIE 10
#define RDS_CMSG_RXPATH_LATENCY 11
#define RDS_INFO_FIRST 10000
diff --git a/net/rds/message.c b/net/rds/message.c
index 25c74b3..111d5a3 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -337,12 +337,14 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
return rm;
}
-int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from)
+int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
+ struct rds_sock *rs, bool zcopy)
{
unsigned long to_copy, nbytes;
unsigned long sg_off;
struct scatterlist *sg;
int ret = 0;
+ int length = iov_iter_count(from);
rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));
@@ -352,6 +354,46 @@ int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from)
sg = rm->data.op_sg;
sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */
+ if (zcopy) {
+ int total_copied = 0;
+ size_t zsize = sizeof(struct rds_znotifier);
+
+ rm->data.op_zcopy = 1;
+ rm->data.op_mmp_znotifier = kzalloc(zsize, GFP_KERNEL);
+ if (!rm->data.op_mmp_znotifier)
+ return -ENOMEM;
+ if (mm_account_pinned_pages(&rm->data.op_mmp_znotifier->z_mmp,
+ length)) {
+ kfree(rm->data.op_mmp_znotifier);
+ rm->data.op_mmp_znotifier = NULL;
+ return -ENOMEM;
+ }
+ while (iov_iter_count(from)) {
+ struct page *pages;
+ size_t start;
+ ssize_t copied;
+
+ copied = iov_iter_get_pages(from, &pages, PAGE_SIZE,
+ 1, &start);
+ if (copied < 0) {
+ /* XXX revert pinning */
+ kfree(rm->data.op_mmp_znotifier);
+ rm->data.op_mmp_znotifier = NULL;
+ return -EFAULT;
+ }
+ total_copied += copied;
+ iov_iter_advance(from, copied);
+ length -= copied;
+ sg_set_page(sg, pages, copied, start);
+ rm->data.op_nents++;
+ sg++;
+ }
+ WARN_ON_ONCE(length != 0);
+ return ret;
+ } /* zcopy */
+
+ rm->data.op_zcopy = 0;
+
while (iov_iter_count(from)) {
if (!sg_page(sg)) {
ret = rds_page_remainder_alloc(sg, iov_iter_count(from),
diff --git a/net/rds/rds.h b/net/rds/rds.h
index de5015a..884d61c 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -781,7 +781,8 @@ void rds_for_each_conn_info(struct socket *sock, unsigned int len,
/* message.c */
struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp);
struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents);
-int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from);
+int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
+ struct rds_sock *rs, bool zcopy);
struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len);
void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
__be16 dport, u64 seq);
diff --git a/net/rds/send.c b/net/rds/send.c
index 5c38ce3..e085730 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -908,6 +908,7 @@ static int rds_rm_size(struct msghdr *msg, int data_len)
case RDS_CMSG_RDMA_DEST:
case RDS_CMSG_RDMA_MAP:
+ case RDS_CMSG_ZCOPY_COOKIE:
cmsg_groups |= 2;
/* these are valid but do no add any size */
break;
@@ -935,6 +936,18 @@ static int rds_rm_size(struct msghdr *msg, int data_len)
return size;
}
+static int rds_cmsg_zcopy(struct rds_sock *rs, struct rds_message *rm,
+ struct cmsghdr *cmsg)
+{
+ unsigned int *cookie;
+
+ if (cmsg->cmsg_len < CMSG_LEN(sizeof(*cookie)))
+ return -EINVAL;
+ cookie = CMSG_DATA(cmsg);
+ rm->data.op_mmp_znotifier->z_cookie = *cookie;
+ return 0;
+}
+
static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
struct msghdr *msg, int *allocated_mr)
{
@@ -977,6 +990,10 @@ static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
ret = rds_cmsg_atomic(rs, rm, cmsg);
break;
+ case RDS_CMSG_ZCOPY_COOKIE:
+ ret = rds_cmsg_zcopy(rs, rm, cmsg);
+ break;
+
default:
return -EINVAL;
}
@@ -1047,10 +1064,12 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
long timeo = sock_sndtimeo(sk, nonblock);
struct rds_conn_path *cpath;
size_t total_payload_len = payload_len, rdma_payload_len = 0;
+ bool zcopy = ((msg->msg_flags & MSG_ZEROCOPY) &&
+ sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY));
/* Mirror Linux UDP mirror of BSD error message compatibility */
/* XXX: Perhaps MSG_MORE someday */
- if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_CMSG_COMPAT)) {
+ if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_CMSG_COMPAT | MSG_ZEROCOPY)) {
ret = -EOPNOTSUPP;
goto out;
}
@@ -1107,12 +1126,14 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
/* Attach data to the rm */
if (payload_len) {
- rm->data.op_sg = rds_message_alloc_sgs(rm, ceil(payload_len, PAGE_SIZE));
+ int num_sgs = ceil(payload_len, PAGE_SIZE);
+
+ rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
if (!rm->data.op_sg) {
ret = -ENOMEM;
goto out;
}
- ret = rds_message_copy_from_user(rm, &msg->msg_iter);
+ ret = rds_message_copy_from_user(rm, &msg->msg_iter, rs, zcopy);
if (ret)
goto out;
}
--
1.7.1
More information about the rds-devel
mailing list