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rds: zerocopy Tx support.

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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 a91dbff551 ("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@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sowmini Varadhan
2018-02-15 10:49:36 -08:00
committed by David S. Miller
parent 01883eda72
commit 0cebaccef3
4 changed files with 91 additions and 8 deletions
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1
include/uapi/linux/rds.h
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@@ -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
#define RDS_INFO_FIRST 10000
#define RDS_INFO_COUNTERS 10000