[Qemu-devel] [PATCH 8/8] qed: Add -o stream=on image creation option

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

Create an image that automatically streams its backing file like this:
qemu-img create -f qed -o backing_file=master.raw,backing_fmt=raw,copy_on_read=on,stream=on stream.qed 60G

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 block/qed.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/block/qed.c b/block/qed.c
index a61cee9..d65abe7 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -461,7 +461,7 @@ static int bdrv_qed_flush(BlockDriverState *bs)
 static int qed_create(const char *filename, uint32_t cluster_size,
                       uint64_t image_size, uint32_t table_size,
                       const char *backing_file, const char *backing_fmt,
-                      bool copy_on_read)
+                      bool copy_on_read, bool stream)
 {
     QEDHeader header = {
         .magic = QED_MAGIC,
@@ -506,6 +506,9 @@ static int qed_create(const char *filename, uint32_t cluster_size,
         if (copy_on_read) {
             header.compat_features |= QED_CF_COPY_ON_READ;
         }
+        if (stream) {
+            header.compat_features |= QED_CF_STREAM;
+        }
     }
 
     qed_header_cpu_to_le(&header, &le_header);
@@ -540,6 +543,7 @@ static int bdrv_qed_create(const char *filename, QEMUOptionParameter *options)
     const char *backing_file = NULL;
     const char *backing_fmt = NULL;
     bool copy_on_read = false;
+    bool stream = false;
 
     while (options && options->name) {
         if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
@@ -560,6 +564,10 @@ static int bdrv_qed_create(const char *filename, QEMUOptionParameter *options)
             if (options->value.n) {
                 copy_on_read = true;
             }
+        } else if (!strcmp(options->name, "stream")) {
+            if (options->value.n) {
+                stream = true;
+            }
         }
         options++;
     }
@@ -585,9 +593,14 @@ static int bdrv_qed_create(const char *filename, QEMUOptionParameter *options)
                 "QED only supports Copy-on-Read with a backing file\n");
         return -EINVAL;
     }
+    if (stream && !copy_on_read) {
+        fprintf(stderr,
+                "QED requires Copy-on-Read to be enabled for streaming\n");
+        return -EINVAL;
+    }
 
     return qed_create(filename, cluster_size, image_size, table_size,
-                      backing_file, backing_fmt, copy_on_read);
+                      backing_file, backing_fmt, copy_on_read, stream);
 }
 
 typedef struct {
@@ -1637,6 +1650,10 @@ static QEMUOptionParameter qed_create_options[] = {
         .name = "copy_on_read",
         .type = OPT_FLAG,
         .help = "Copy blocks from base image on read"
+    }, {
+        .name = "stream",
+        .type = OPT_FLAG,
+        .help = "Start copying blocks from base image once opened"
     },
     { /* end of list */ }
 };
-- 
1.7.4.4