On 2/14/2018 2:28 AM, Sowmini Varadhan wrote:
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.varad...@oracle.com>
---
v2:
- remove unused data_len argument to rds_rm_size;
- unmap as necessary if we fail in the middle of zerocopy setup
include/uapi/linux/rds.h | 1 +
net/rds/message.c | 51 +++++++++++++++++++++++++++++++++++++++++++++-
net/rds/rds.h | 3 +-
net/rds/send.c | 44 ++++++++++++++++++++++++++++++++++-----
4 files changed, 91 insertions(+), 8 deletions(-)
diff --git a/include/uapi/linux/rds.h b/include/uapi/linux/rds.h
index e71d449..12e3bca 100644
--- a/include/uapi/linux/rds.h
+++ b/include/uapi/linux/rds.h
@@ -103,6 +103,7 @@
#define RDS_CMSG_MASKED_ATOMIC_FADD 8
#define RDS_CMSG_MASKED_ATOMIC_CSWP 9
#define RDS_CMSG_RXPATH_LATENCY 11
+#define RDS_CMSG_ZCOPY_COOKIE 12
s/RDS_CMSG_ZCOPY_COOKIE/RDS_CMSG_ZMSGCOPY_COOKIE
#define RDS_INFO_FIRST 10000
#define RDS_INFO_COUNTERS 10000
diff --git a/net/rds/message.c b/net/rds/message.c
index d874b74..e499566 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -341,12 +341,14 @@ 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,
+ 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));
@@ -356,6 +358,53 @@ 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;
+ struct sk_buff *skb;
+
+ skb = alloc_skb(SO_EE_ORIGIN_MAX_ZCOOKIES * sizeof(u32),
+ GFP_KERNEL);
This can sleep so you might want to check if you want to use ATOMIC
version here.
+ if (!skb)
+ return -ENOMEM;
+ rm->data.op_mmp_znotifier = RDS_ZCOPY_SKB(skb);
+ memset(rm->data.op_mmp_znotifier, 0,
+ sizeof(*rm->data.op_mmp_znotifier));
+ if (mm_account_pinned_pages(&rm->data.op_mmp_znotifier->z_mmp,
+ length)) {
+ consume_skb(skb);
+ rm->data.op_mmp_znotifier = NULL;
+ return -ENOMEM;
+ }
NOMEM new application visible change but probably the right one for this
particular case. Just need to make sure application can handle this
error.
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 6e8fc4c..dfdc9b3 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -784,7 +784,8 @@ 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,
+ 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 5ac0925..80171cf 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
[...]
@@ -1087,8 +1112,15 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg,
size_t payload_len)
goto out;
}
+ if (zcopy) {
+ if (rs->rs_transport->t_type != RDS_TRANS_TCP) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
+ num_sgs = iov_iter_npages(&msg->msg_iter, INT_MAX);
+ }
Instead of this transport check, lets move this under transport function
which then can be populated by TCP transport.
Rest of the changes looks good.
Regards,
Santosh
