From cda3fcf14f2883fea633e25256f6c14a71271adf Mon Sep 17 00:00:00 2001

From: Leonardo Bras <leobras@redhat.com>

Date: Fri, 13 May 2022 03:28:31 -0300

Subject: [PATCH 08/18] QIOChannel: Add flags on io_writev and introduce

 io_flush callback

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RH-Author: Leonardo Brás <leobras@redhat.com>

RH-MergeRequest: 95: MSG_ZEROCOPY + Multifd

RH-Commit: [2/11] 06acfb6b0cb2c25733c2eb198011f7623b5a7024 (LeoBras/centos-qemu-kvm)

RH-Bugzilla: 1968509

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

RH-Acked-by: Peter Xu <peterx@redhat.com>

Add flags to io_writev and introduce io_flush as optional callback to

QIOChannelClass, allowing the implementation of zero copy writes by

subclasses.

How to use them:

- Write data using qio_channel_writev*(...,QIO_CHANNEL_WRITE_FLAG_ZERO_COPY),

- Wait write completion with qio_channel_flush().

Notes:

As some zero copy write implementations work asynchronously, it's

recommended to keep the write buffer untouched until the return of

qio_channel_flush(), to avoid the risk of sending an updated buffer

instead of the buffer state during write.

As io_flush callback is optional, if a subclass does not implement it, then:

- io_flush will return 0 without changing anything.

Also, some functions like qio_channel_writev_full_all() were adapted to

receive a flag parameter. That allows shared code between zero copy and

non-zero copy writev, and also an easier implementation on new flags.

Signed-off-by: Leonardo Bras <leobras@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Message-Id: <20220513062836.965425-3-leobras@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit b88651cb4d4fa416fdbb6afaf5b26ec8c035eaad)

Signed-off-by: Leonardo Bras <leobras@redhat.com>

---

 chardev/char-io.c                   |  2 +-

 hw/remote/mpqemu-link.c             |  2 +-

 include/io/channel.h                | 38 +++++++++++++++++++++-

 io/channel-buffer.c                 |  1 +

 io/channel-command.c                |  1 +

 io/channel-file.c                   |  1 +

 io/channel-socket.c                 |  2 ++

 io/channel-tls.c                    |  1 +

 io/channel-websock.c                |  1 +

 io/channel.c                        | 49 +++++++++++++++++++++++------

 migration/rdma.c                    |  1 +

 scsi/pr-manager-helper.c            |  2 +-

 tests/unit/test-io-channel-socket.c |  1 +

 13 files changed, 88 insertions(+), 14 deletions(-)

diff --git a/chardev/char-io.c b/chardev/char-io.c

index 8ced184160..4451128cba 100644

--- a/chardev/char-io.c

+++ b/chardev/char-io.c

@@ -122,7 +122,7 @@ int io_channel_send_full(QIOChannel *ioc,

         ret = qio_channel_writev_full(

             ioc, &iov, 1,

-            fds, nfds, NULL);

+            fds, nfds, 0, NULL);

         if (ret == QIO_CHANNEL_ERR_BLOCK) {

             if (offset) {

                 return offset;

diff --git a/hw/remote/mpqemu-link.c b/hw/remote/mpqemu-link.c

index 7e841820e5..e8f556bd27 100644

--- a/hw/remote/mpqemu-link.c

+++ b/hw/remote/mpqemu-link.c

@@ -69,7 +69,7 @@ bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)

     }

     if (!qio_channel_writev_full_all(ioc, send, G_N_ELEMENTS(send),

-                                    fds, nfds, errp)) {

+                                    fds, nfds, 0, errp)) {

         ret = true;

     } else {

         trace_mpqemu_send_io_error(msg->cmd, msg->size, nfds);

diff --git a/include/io/channel.h b/include/io/channel.h

index 88988979f8..c680ee7480 100644

--- a/include/io/channel.h

+++ b/include/io/channel.h

@@ -32,12 +32,15 @@ OBJECT_DECLARE_TYPE(QIOChannel, QIOChannelClass,

 #define QIO_CHANNEL_ERR_BLOCK -2

+#define QIO_CHANNEL_WRITE_FLAG_ZERO_COPY 0x1

+

 typedef enum QIOChannelFeature QIOChannelFeature;

 enum QIOChannelFeature {

     QIO_CHANNEL_FEATURE_FD_PASS,

     QIO_CHANNEL_FEATURE_SHUTDOWN,

     QIO_CHANNEL_FEATURE_LISTEN,

+    QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY,

 };

@@ -104,6 +107,7 @@ struct QIOChannelClass {

                          size_t niov,

                          int *fds,

                          size_t nfds,

+                         int flags,

                          Error **errp);

     ssize_t (*io_readv)(QIOChannel *ioc,

                         const struct iovec *iov,

@@ -136,6 +140,8 @@ struct QIOChannelClass {

                                   IOHandler *io_read,

                                   IOHandler *io_write,

                                   void *opaque);

+    int (*io_flush)(QIOChannel *ioc,

+                    Error **errp);

 };

 /* General I/O handling functions */

@@ -228,6 +234,7 @@ ssize_t qio_channel_readv_full(QIOChannel *ioc,

  * @niov: the length of the @iov array

  * @fds: an array of file handles to send

  * @nfds: number of file handles in @fds

+ * @flags: write flags (QIO_CHANNEL_WRITE_FLAG_*)

  * @errp: pointer to a NULL-initialized error object

  *

  * Write data to the IO channel, reading it from the

@@ -260,6 +267,7 @@ ssize_t qio_channel_writev_full(QIOChannel *ioc,

                                 size_t niov,

                                 int *fds,

                                 size_t nfds,

+                                int flags,

                                 Error **errp);

 /**

@@ -837,6 +845,7 @@ int qio_channel_readv_full_all(QIOChannel *ioc,

  * @niov: the length of the @iov array

  * @fds: an array of file handles to send

  * @nfds: number of file handles in @fds

+ * @flags: write flags (QIO_CHANNEL_WRITE_FLAG_*)

  * @errp: pointer to a NULL-initialized error object

  *

  *

@@ -846,6 +855,14 @@ int qio_channel_readv_full_all(QIOChannel *ioc,

  * to be written, yielding from the current coroutine

  * if required.

  *

+ * If QIO_CHANNEL_WRITE_FLAG_ZERO_COPY is passed in flags,

+ * instead of waiting for all requested data to be written,

+ * this function will wait until it's all queued for writing.

+ * In this case, if the buffer gets changed between queueing and

+ * sending, the updated buffer will be sent. If this is not a

+ * desired behavior, it's suggested to call qio_channel_flush()

+ * before reusing the buffer.

+ *

  * Returns: 0 if all bytes were written, or -1 on error

  */

@@ -853,6 +870,25 @@ int qio_channel_writev_full_all(QIOChannel *ioc,

                                 const struct iovec *iov,

                                 size_t niov,

                                 int *fds, size_t nfds,

-                                Error **errp);

+                                int flags, Error **errp);

+

+/**

+ * qio_channel_flush:

+ * @ioc: the channel object

+ * @errp: pointer to a NULL-initialized error object

+ *

+ * Will block until every packet queued with

+ * qio_channel_writev_full() + QIO_CHANNEL_WRITE_FLAG_ZERO_COPY

+ * is sent, or return in case of any error.

+ *

+ * If not implemented, acts as a no-op, and returns 0.

+ *

+ * Returns -1 if any error is found,

+ *          1 if every send failed to use zero copy.

+ *          0 otherwise.

+ */

+

+int qio_channel_flush(QIOChannel *ioc,

+                      Error **errp);

 #endif /* QIO_CHANNEL_H */

diff --git a/io/channel-buffer.c b/io/channel-buffer.c

index baa4e2b089..bf52011be2 100644

--- a/io/channel-buffer.c

+++ b/io/channel-buffer.c

@@ -81,6 +81,7 @@ static ssize_t qio_channel_buffer_writev(QIOChannel *ioc,

                                          size_t niov,

                                          int *fds,

                                          size_t nfds,

+                                         int flags,

                                          Error **errp)

 {

     QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);

diff --git a/io/channel-command.c b/io/channel-command.c

index 338da73ade..54560464ae 100644

--- a/io/channel-command.c

+++ b/io/channel-command.c

@@ -258,6 +258,7 @@ static ssize_t qio_channel_command_writev(QIOChannel *ioc,

                                           size_t niov,

                                           int *fds,

                                           size_t nfds,

+                                          int flags,

                                           Error **errp)

 {

     QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);

diff --git a/io/channel-file.c b/io/channel-file.c

index d7cf6d278f..ef6807a6be 100644

--- a/io/channel-file.c

+++ b/io/channel-file.c

@@ -114,6 +114,7 @@ static ssize_t qio_channel_file_writev(QIOChannel *ioc,

                                        size_t niov,

                                        int *fds,

                                        size_t nfds,

+                                       int flags,

                                        Error **errp)

 {

     QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);

diff --git a/io/channel-socket.c b/io/channel-socket.c

index 7a8d9f69c9..a1be2197ca 100644

--- a/io/channel-socket.c

+++ b/io/channel-socket.c

@@ -525,6 +525,7 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc,

                                          size_t niov,

                                          int *fds,

                                          size_t nfds,

+                                         int flags,

                                          Error **errp)

 {

     QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);

@@ -620,6 +621,7 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc,

                                          size_t niov,

                                          int *fds,

                                          size_t nfds,

+                                         int flags,

                                          Error **errp)

 {

     QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);

diff --git a/io/channel-tls.c b/io/channel-tls.c

index 2ae1b92fc0..4ce890a538 100644

--- a/io/channel-tls.c

+++ b/io/channel-tls.c

@@ -301,6 +301,7 @@ static ssize_t qio_channel_tls_writev(QIOChannel *ioc,

                                       size_t niov,

                                       int *fds,

                                       size_t nfds,

+                                      int flags,

                                       Error **errp)

 {

     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(ioc);

diff --git a/io/channel-websock.c b/io/channel-websock.c

index 55145a6a8c..9619906ac3 100644

--- a/io/channel-websock.c

+++ b/io/channel-websock.c

@@ -1127,6 +1127,7 @@ static ssize_t qio_channel_websock_writev(QIOChannel *ioc,

                                           size_t niov,

                                           int *fds,

                                           size_t nfds,

+                                          int flags,

                                           Error **errp)

 {

     QIOChannelWebsock *wioc = QIO_CHANNEL_WEBSOCK(ioc);

diff --git a/io/channel.c b/io/channel.c

index e8b019dc36..0640941ac5 100644

--- a/io/channel.c

+++ b/io/channel.c

@@ -72,18 +72,32 @@ ssize_t qio_channel_writev_full(QIOChannel *ioc,

                                 size_t niov,

                                 int *fds,

                                 size_t nfds,

+                                int flags,

                                 Error **errp)

 {

     QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);

-    if ((fds || nfds) &&

-        !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_FD_PASS)) {

+    if (fds || nfds) {

+        if (!qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_FD_PASS)) {

+            error_setg_errno(errp, EINVAL,

+                             "Channel does not support file descriptor passing");

+            return -1;

+        }

+        if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {

+            error_setg_errno(errp, EINVAL,

+                             "Zero Copy does not support file descriptor passing");

+            return -1;

+        }

+    }

+

+    if ((flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) &&

+        !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY)) {

         error_setg_errno(errp, EINVAL,

-                         "Channel does not support file descriptor passing");

+                         "Requested Zero Copy feature is not available");

         return -1;

     }

-    return klass->io_writev(ioc, iov, niov, fds, nfds, errp);

+    return klass->io_writev(ioc, iov, niov, fds, nfds, flags, errp);

 }

@@ -217,14 +231,14 @@ int qio_channel_writev_all(QIOChannel *ioc,

                            size_t niov,

                            Error **errp)

 {

-    return qio_channel_writev_full_all(ioc, iov, niov, NULL, 0, errp);

+    return qio_channel_writev_full_all(ioc, iov, niov, NULL, 0, 0, errp);

 }

 int qio_channel_writev_full_all(QIOChannel *ioc,

                                 const struct iovec *iov,

                                 size_t niov,

                                 int *fds, size_t nfds,

-                                Error **errp)

+                                int flags, Error **errp)

 {

     int ret = -1;

     struct iovec *local_iov = g_new(struct iovec, niov);

@@ -237,8 +251,10 @@ int qio_channel_writev_full_all(QIOChannel *ioc,

     while (nlocal_iov > 0) {

         ssize_t len;

-        len = qio_channel_writev_full(ioc, local_iov, nlocal_iov, fds, nfds,

-                                      errp);

+

+        len = qio_channel_writev_full(ioc, local_iov, nlocal_iov, fds,

+                                            nfds, flags, errp);

+

         if (len == QIO_CHANNEL_ERR_BLOCK) {

             if (qemu_in_coroutine()) {

                 qio_channel_yield(ioc, G_IO_OUT);

@@ -277,7 +293,7 @@ ssize_t qio_channel_writev(QIOChannel *ioc,

                            size_t niov,

                            Error **errp)

 {

-    return qio_channel_writev_full(ioc, iov, niov, NULL, 0, errp);

+    return qio_channel_writev_full(ioc, iov, niov, NULL, 0, 0, errp);

 }

@@ -297,7 +313,7 @@ ssize_t qio_channel_write(QIOChannel *ioc,

                           Error **errp)

 {

     struct iovec iov = { .iov_base = (char *)buf, .iov_len = buflen };

-    return qio_channel_writev_full(ioc, &iov, 1, NULL, 0, errp);

+    return qio_channel_writev_full(ioc, &iov, 1, NULL, 0, 0, errp);

 }

@@ -473,6 +489,19 @@ off_t qio_channel_io_seek(QIOChannel *ioc,

     return klass->io_seek(ioc, offset, whence, errp);

 }

+int qio_channel_flush(QIOChannel *ioc,

+                                Error **errp)

+{

+    QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);

+

+    if (!klass->io_flush ||

+        !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY)) {

+        return 0;

+    }

+

+    return klass->io_flush(ioc, errp);

+}

+

 static void qio_channel_restart_read(void *opaque)

 {

diff --git a/migration/rdma.c b/migration/rdma.c

index ef1e65ec36..672d1958a9 100644

--- a/migration/rdma.c

+++ b/migration/rdma.c

@@ -2840,6 +2840,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,

                                        size_t niov,

                                        int *fds,

                                        size_t nfds,

+                                       int flags,

                                        Error **errp)

 {

     QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);

diff --git a/scsi/pr-manager-helper.c b/scsi/pr-manager-helper.c

index 451c7631b7..3be52a98d5 100644

--- a/scsi/pr-manager-helper.c

+++ b/scsi/pr-manager-helper.c

@@ -77,7 +77,7 @@ static int pr_manager_helper_write(PRManagerHelper *pr_mgr,

         iov.iov_base = (void *)buf;

         iov.iov_len = sz;

         n_written = qio_channel_writev_full(QIO_CHANNEL(pr_mgr->ioc), &iov, 1,

-                                            nfds ? &fd : NULL, nfds, errp);

+                                            nfds ? &fd : NULL, nfds, 0, errp);

         if (n_written <= 0) {

             assert(n_written != QIO_CHANNEL_ERR_BLOCK);

diff --git a/tests/unit/test-io-channel-socket.c b/tests/unit/test-io-channel-socket.c

index c49eec1f03..6713886d02 100644

--- a/tests/unit/test-io-channel-socket.c

+++ b/tests/unit/test-io-channel-socket.c

@@ -444,6 +444,7 @@ static void test_io_channel_unix_fd_pass(void)

                             G_N_ELEMENTS(iosend),

                             fdsend,

                             G_N_ELEMENTS(fdsend),

+                            0,

                             &error_abort);

     qio_channel_readv_full(dst,

-- 

2.35.3