[Qemu-devel] [PATCH v3 07/27] migration: introduce a new QEMUFile impl based on QIOChannel

["Daniel P. Berrange" <berrange@redhat.com>]

Introduce a new QEMUFile implementation that is based on
the QIOChannel objects. This impl is different from existing
impls in that there is no file descriptor that can be made
available, as some channels may be based on higher level
protocols such as TLS.

Although the QIOChannel based implementation can trivially
provide a bi-directional stream, initially we have separate
functions for opening input & output directions to fit with
the expectation of the current QEMUFile interface.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 include/migration/qemu-file.h |   4 +
 migration/Makefile.objs       |   1 +
 migration/qemu-file-channel.c | 204 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 209 insertions(+)
 create mode 100644 migration/qemu-file-channel.c

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 2dea81f..0329ccc 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -23,7 +23,9 @@
  */
 #ifndef QEMU_FILE_H
 #define QEMU_FILE_H 1
+#include "qemu-common.h"
 #include "exec/cpu-common.h"
+#include "io/channel.h"
 
 
 /* This function writes a chunk of data to a file at the given position.
@@ -135,6 +137,8 @@ QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops);
 QEMUFile *qemu_fopen(const char *filename, const char *mode);
 QEMUFile *qemu_fdopen(int fd, const char *mode);
 QEMUFile *qemu_fopen_socket(int fd, const char *mode);
+QEMUFile *qemu_fopen_channel_input(QIOChannel *ioc);
+QEMUFile *qemu_fopen_channel_output(QIOChannel *ioc);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
 QEMUFile *qemu_bufopen(const char *mode, QEMUSizedBuffer *input);
 void qemu_file_set_hooks(QEMUFile *f, const QEMUFileHooks *hooks);
diff --git a/migration/Makefile.objs b/migration/Makefile.objs
index 0cac6d7..b357e2f 100644
--- a/migration/Makefile.objs
+++ b/migration/Makefile.objs
@@ -1,6 +1,7 @@
 common-obj-y += migration.o tcp.o
 common-obj-y += vmstate.o
 common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o
+common-obj-y += qemu-file-channel.o
 common-obj-y += xbzrle.o postcopy-ram.o
 
 common-obj-$(CONFIG_RDMA) += rdma.o
diff --git a/migration/qemu-file-channel.c b/migration/qemu-file-channel.c
new file mode 100644
index 0000000..10990e8
--- /dev/null
+++ b/migration/qemu-file-channel.c
@@ -0,0 +1,204 @@
+/*
+ * QEMUFile backend for QIOChannel objects
+ *
+ * Copyright (c) 2015-2016 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "migration/qemu-file.h"
+#include "io/channel-socket.h"
+#include "qemu/iov.h"
+
+
+/**
+ * @skip: number of bytes to advance head of @iov
+ * @iov: pointer to iov array, updated on success
+ * @iovcnt: number of elements in @iov, updated on success
+ * @oldiov: pointer single element to hold old info from @iov
+ *
+ * This will update @iov so that its head is advanced
+ * by @skip bytes. To do this, zero or more complete
+ * elements of @iov will be skipped over. The new head
+ * of @iov will then have its base & len updated to
+ * skip the remaining number of bytes. @oldiov will
+ * hold the original data from the new head of @iov.
+ */
+static void channel_skip_iov(size_t skip,
+                             struct iovec **iov,
+                             int *iovcnt,
+                             struct iovec *oldiov)
+{
+    ssize_t done = 0;
+    size_t i;
+    for (i = 0; i < *iovcnt; i++) {
+        if ((*iov)[i].iov_len <= skip) {
+            done += (*iov)[i].iov_len;
+            skip -= (*iov)[i].iov_len;
+        } else {
+            done += skip;
+            oldiov->iov_base = (*iov)[i].iov_base;
+            oldiov->iov_len = (*iov)[i].iov_len;
+            (*iov)[i].iov_len -= skip;
+            (*iov)[i].iov_base += skip;
+            *iov = *iov + i;
+            *iovcnt = *iovcnt - i;
+            break;
+        }
+    }
+}
+
+static ssize_t channel_writev_buffer(void *opaque,
+                                     struct iovec *iov,
+                                     int iovcnt,
+                                     int64_t pos)
+{
+    QIOChannel *ioc = QIO_CHANNEL(opaque);
+    ssize_t done = 0;
+    ssize_t want = iov_size(iov, iovcnt);
+    struct iovec oldiov = { NULL, 0 };
+
+    while (done < want) {
+        ssize_t len;
+        struct iovec *cur = iov;
+        int curcnt = iovcnt;
+
+        channel_skip_iov(done, &cur, &curcnt, &oldiov);
+
+        len = qio_channel_writev(ioc, cur, curcnt, NULL);
+        if (oldiov.iov_base) {
+            /* Restore original caller's info in @iov */
+            cur[0].iov_base = oldiov.iov_base;
+            cur[0].iov_len = oldiov.iov_len;
+            oldiov.iov_base = NULL;
+            oldiov.iov_len = 0;
+        }
+        if (len == QIO_CHANNEL_ERR_BLOCK) {
+            qio_channel_wait(ioc, G_IO_OUT);
+            continue;
+        }
+        if (len < 0) {
+            /* XXX handle Error objects */
+            return -EIO;
+        }
+
+        done += len;
+    }
+    return done;
+}
+
+
+static ssize_t channel_get_buffer(void *opaque,
+                                  uint8_t *buf,
+                                  int64_t pos,
+                                  size_t size)
+{
+    QIOChannel *ioc = QIO_CHANNEL(opaque);
+    ssize_t ret;
+
+    do {
+        ret = qio_channel_read(ioc, (char *)buf, size, NULL);
+        if (ret < 0) {
+            if (ret == QIO_CHANNEL_ERR_BLOCK) {
+                qio_channel_yield(ioc, G_IO_IN);
+            } else {
+                /* XXX handle Error * object */
+                return -EIO;
+            }
+        }
+    } while (ret == QIO_CHANNEL_ERR_BLOCK);
+
+    return ret;
+}
+
+
+static int channel_close(void *opaque)
+{
+    QIOChannel *ioc = QIO_CHANNEL(opaque);
+    qio_channel_close(ioc, NULL);
+    object_unref(OBJECT(ioc));
+    return 0;
+}
+
+
+static int channel_shutdown(void *opaque,
+                            bool rd,
+                            bool wr)
+{
+    QIOChannel *ioc = QIO_CHANNEL(opaque);
+
+    if (qio_channel_has_feature(ioc,
+                                QIO_CHANNEL_FEATURE_SHUTDOWN)) {
+        QIOChannelShutdown mode;
+        if (rd && wr) {
+            mode = QIO_CHANNEL_SHUTDOWN_BOTH;
+        } else if (rd) {
+            mode = QIO_CHANNEL_SHUTDOWN_READ;
+        } else {
+            mode = QIO_CHANNEL_SHUTDOWN_WRITE;
+        }
+        if (qio_channel_shutdown(ioc, mode, NULL) < 0) {
+            /* XXX handler Error * object */
+            return -EIO;
+        }
+    }
+    return 0;
+}
+
+
+static int channel_set_blocking(void *opaque,
+                                bool enabled)
+{
+    QIOChannel *ioc = QIO_CHANNEL(opaque);
+
+    if (qio_channel_set_blocking(ioc, enabled, NULL) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+
+static const QEMUFileOps channel_input_ops = {
+    .get_buffer = channel_get_buffer,
+    .close = channel_close,
+    .shut_down = channel_shutdown,
+    .set_blocking = channel_set_blocking,
+};
+
+
+static const QEMUFileOps channel_output_ops = {
+    .writev_buffer = channel_writev_buffer,
+    .close = channel_close,
+    .shut_down = channel_shutdown,
+    .set_blocking = channel_set_blocking,
+};
+
+
+QEMUFile *qemu_fopen_channel_input(QIOChannel *ioc)
+{
+    object_ref(OBJECT(ioc));
+    return qemu_fopen_ops(ioc, &channel_input_ops);
+}
+
+QEMUFile *qemu_fopen_channel_output(QIOChannel *ioc)
+{
+    object_ref(OBJECT(ioc));
+    return qemu_fopen_ops(ioc, &channel_output_ops);
+}
-- 
2.5.0