[PATCH net-next v2 15/17] iscsi: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage

[David Howells]

Use sendmsg() with MSG_SPLICE_PAGES rather than sendpage. This allows
multiple pages and multipage folios to be passed through.

TODO: iscsit_fe_sendpage_sg() should perhaps set up a bio_vec array for the
entire set of pages it's going to transfer plus two for the header and
trailer and page fragments to hold the header and trailer - and then call
sendmsg once for the entire message.

Signed-off-by: David Howells <dhow...@redhat.com>
cc: Lee Duncan <ldu...@suse.com>
cc: Chris Leech <cle...@redhat.com>
cc: Mike Christie <michael....@oracle.com>
cc: Maurizio Lombardi <mlom...@redhat.com>
cc: "James E.J. Bottomley" <je...@linux.ibm.com>
cc: "Martin K. Petersen" <martin....@oracle.com>
cc: "David S. Miller" <da...@davemloft.net>
cc: Eric Dumazet <edum...@google.com>
cc: Jakub Kicinski <ku...@kernel.org>
cc: Paolo Abeni <pab...@redhat.com>
cc: Jens Axboe <ax...@kernel.dk>
cc: Matthew Wilcox <wi...@infradead.org>
cc: Al Viro <vi...@zeniv.linux.org.uk>
cc: open-...@googlegroups.com
cc: linux...@vger.kernel.org
cc: target...@vger.kernel.org
cc: net...@vger.kernel.org
---

Notes:
ver #2)
- Wrap lines at 80.

drivers/scsi/iscsi_tcp.c | 26 +++++++++---------------
drivers/scsi/iscsi_tcp.h | 2 +-
drivers/target/iscsi/iscsi_target_util.c | 15 ++++++++------
3 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 9637d4bc2bc9..9ab8555180a3 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -301,35 +301,32 @@ static int iscsi_sw_tcp_xmit_segment(struct iscsi_tcp_conn *tcp_conn,

while (!iscsi_tcp_segment_done(tcp_conn, segment, 0, r)) {
struct scatterlist *sg;
+ struct msghdr msg = {};
+ struct bio_vec bv;
unsigned int offset, copy;
- int flags = 0;

r = 0;
offset = segment->copied;
copy = segment->size - offset;

if (segment->total_copied + segment->size < segment->total_size)
- flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
+ msg.msg_flags |= MSG_MORE;

if (tcp_sw_conn->queue_recv)
- flags |= MSG_DONTWAIT;
+ msg.msg_flags |= MSG_DONTWAIT;

- /* Use sendpage if we can; else fall back to sendmsg */
if (!segment->data) {
+ if (!tcp_conn->iscsi_conn->datadgst_en)
+ msg.msg_flags |= MSG_SPLICE_PAGES;
sg = segment->sg;
offset += segment->sg_offset + sg->offset;
- r = tcp_sw_conn->sendpage(sk, sg_page(sg), offset,
- copy, flags);
+ bvec_set_page(&bv, sg_page(sg), copy, offset);
} else {
- struct msghdr msg = { .msg_flags = flags };
- struct kvec iov = {
- .iov_base = segment->data + offset,
- .iov_len = copy
- };
-
- r = kernel_sendmsg(sk, &msg, &iov, 1, copy);
+ bvec_set_virt(&bv, segment->data + offset, copy);
}
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bv, 1, copy);

+ r = sock_sendmsg(sk, &msg);
if (r < 0) {
iscsi_tcp_segment_unmap(segment);
return r;
@@ -746,7 +743,6 @@ iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
sock_no_linger(sk);

iscsi_sw_tcp_conn_set_callbacks(conn);
- tcp_sw_conn->sendpage = tcp_sw_conn->sock->ops->sendpage;
/*
* set receive state machine into initial state
*/
@@ -777,8 +773,6 @@ static int iscsi_sw_tcp_conn_set_param(struct iscsi_cls_conn *cls_conn,
return -ENOTCONN;
}
iscsi_set_param(cls_conn, param, buf, buflen);
- tcp_sw_conn->sendpage = conn->datadgst_en ?
- sock_no_sendpage : tcp_sw_conn->sock->ops->sendpage;
mutex_unlock(&tcp_sw_conn->sock_lock);
break;
case ISCSI_PARAM_MAX_R2T:
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 68e14a344904..d6ec08d7eb63 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -48,7 +48,7 @@ struct iscsi_sw_tcp_conn {
uint32_t sendpage_failures_cnt;
uint32_t discontiguous_hdr_cnt;

- ssize_t (*sendpage)(struct socket *, struct page *, int, size_t, int);
+ bool can_splice_to_tcp;
};

struct iscsi_sw_tcp_host {
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index b14835fcb033..6231fa4ef5c6 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -1129,6 +1129,8 @@ int iscsit_fe_sendpage_sg(
struct iscsit_conn *conn)
{
struct scatterlist *sg = cmd->first_data_sg;
+ struct bio_vec bvec;
+ struct msghdr msghdr = { .msg_flags = MSG_SPLICE_PAGES, };
struct kvec iov;
u32 tx_hdr_size, data_len;
u32 offset = cmd->first_data_sg_off;
@@ -1172,17 +1174,18 @@ int iscsit_fe_sendpage_sg(
u32 space = (sg->length - offset);
u32 sub_len = min_t(u32, data_len, space);
send_pg:
- tx_sent = conn->sock->ops->sendpage(conn->sock,
- sg_page(sg), sg->offset + offset, sub_len, 0);
+ bvec_set_page(&bvec, sg_page(sg), sub_len, sg->offset + offset);
+ iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, sub_len);
+
+ tx_sent = conn->sock->ops->sendmsg(conn->sock, &msghdr,
+ sub_len);
if (tx_sent != sub_len) {
if (tx_sent == -EAGAIN) {
- pr_err("tcp_sendpage() returned"
- " -EAGAIN\n");
+ pr_err("sendmsg/splice returned -EAGAIN\n");
goto send_pg;
}

- pr_err("tcp_sendpage() failure: %d\n",
- tx_sent);
+ pr_err("sendmsg/splice failure: %d\n", tx_sent);
return -1;
}

[David Howells]

[David Howells]

drivers/scsi/iscsi_tcp.h | 2 --
drivers/target/iscsi/iscsi_target_util.c | 15 ++++++++------
3 files changed, 19 insertions(+), 24 deletions(-)

index 68e14a344904..89a6fc552f0b 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -47,8 +47,6 @@ struct iscsi_sw_tcp_conn {
/* MIB custom statistics */

uint32_t sendpage_failures_cnt;
uint32_t discontiguous_hdr_cnt;
-
- ssize_t (*sendpage)(struct socket *, struct page *, int, size_t, int);

[Mike Christie]

When you send this again can you split it into 2 patches?

drivers/scsi/iscsi_tcp.* is one driver. It's similar to a NFS client and
it has a set of maintainers that you saw in the MAINTAINER file.

drivers/target/iscsi/iscsi_target_util.c is another driver which is similar
to a NFS server. Martin is the overall maintainer but it's a group effort
to review patches.

I've tested and reviewed the iscsi_tcp parts. You can add my:

Reviewed-by: Mike Christie <michael....@oracle.com>

For the iscsi_target_util.c part, I'm reviewing it now and hoping Maurizio
and/or Dimitry might review as well.

One question on the target part I had is about the TODO above. Is that
something you were going to do, or is it something you are asking the target
people to do?

[David Howells]

Mike Christie <michael....@oracle.com> wrote:

>
> One question on the target part I had is about the TODO above. Is that
> something you were going to do, or is it something you are asking the target
> people to do?

I've got an in-progress patch for that, but it's not the simplest code to
modify. I'm holding off on completing it till the simpler cleanup is in. I
might end up having to push the incomplete patch your way to ask for advice on
how to complete it.

David