[Qemu-devel] [PATCH v3 7/9] Add qemu_put_buffer_no_copy

[Orit Wasserman <owasserm@redhat.com>]

This allow us to add a buffer to the iovec to send without copying it
into the static buffer.

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
---
 include/migration/qemu-file.h |  5 +++++
 savevm.c                      | 37 ++++++++++++++++++++++++++++---------
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 8d3da9b..5168be2 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -75,6 +75,11 @@ int qemu_fclose(QEMUFile *f);
 int64_t qemu_ftell(QEMUFile *f);
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
 void qemu_put_byte(QEMUFile *f, int v);
+/*
+ * put_buffer without copying the buffer.
+ * The buffer should be available till it is sent.
+ */
+void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size);
 
 static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
 {
diff --git a/savevm.c b/savevm.c
index 83aa9e7..fbfb9e3 100644
--- a/savevm.c
+++ b/savevm.c
@@ -621,6 +621,30 @@ int qemu_fclose(QEMUFile *f)
     return ret;
 }
 
+
+void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size)
+{
+    if (f->last_error) {
+        return;
+    }
+
+    if (f->is_write == 0 && f->buf_index > 0) {
+        fprintf(stderr,
+                "Attempted to write to buffer while read buffer is not empty\n");
+        abort();
+    }
+
+    f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
+    f->iov[f->iovcnt++].iov_len = size;
+
+    f->is_write = 1;
+    f->bytes_xfer += size;
+
+    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
+        qemu_fflush(f);
+    }
+}
+
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
 {
     int l;
@@ -640,19 +664,14 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
         if (l > size)
             l = size;
         memcpy(f->buf + f->buf_index, buf, l);
-        f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
-        f->iov[f->iovcnt++].iov_len = l;
         f->is_write = 1;
         f->buf_index += l;
-        f->bytes_xfer += l;
+        qemu_put_buffer_no_copy(f, f->buf + (f->buf_index - l), l);
+        if (qemu_file_get_error(f)) {
+            break;
+        }
         buf += l;
         size -= l;
-        if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
-            qemu_fflush(f);
-            if (qemu_file_get_error(f)) {
-                break;
-            }
-        }
     }
 }
 
-- 
1.7.11.7