scsi: target: iscsi: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage

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 <dhowells@redhat.com>
cc: Mike Christie <michael.christie@oracle.com>
cc: Maurizio Lombardi <mlombard@redhat.com>
cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
cc: "Martin K. Petersen" <martin.petersen@oracle.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: open-iscsi@googlegroups.com
Link: https://lore.kernel.org/r/20230623225513.2732256-13-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index b14835f..6231fa4 100644 (file)
--- 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 @@ send_hdr:
                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;
                }