[Qemu-devel] [PATCH 6/8] blockdev: Allow image files to auto-enable streaming

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

Image files that having streaming enabled will automatically begin
streaming when opened.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 block.c     |    5 +++++
 block.h     |    1 +
 block_int.h |    1 +
 blockdev.c  |    9 +++++++++
 4 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 5e3476c..68a97a3 100644
--- a/block.c
+++ b/block.c
@@ -1584,6 +1584,11 @@ const char *bdrv_get_device_name(BlockDriverState *bs)
     return bs->device_name;
 }
 
+int bdrv_stream_enabled(BlockDriverState *bs)
+{
+    return bs->stream;
+}
+
 int bdrv_flush(BlockDriverState *bs)
 {
     if (bs->open_flags & BDRV_O_NO_FLUSH) {
diff --git a/block.h b/block.h
index fad828a..3357c50 100644
--- a/block.h
+++ b/block.h
@@ -189,6 +189,7 @@ int bdrv_is_removable(BlockDriverState *bs);
 int bdrv_is_read_only(BlockDriverState *bs);
 int bdrv_is_sg(BlockDriverState *bs);
 int bdrv_enable_write_cache(BlockDriverState *bs);
+int bdrv_stream_enabled(BlockDriverState *bs);
 int bdrv_is_inserted(BlockDriverState *bs);
 int bdrv_media_changed(BlockDriverState *bs);
 int bdrv_is_locked(BlockDriverState *bs);
diff --git a/block_int.h b/block_int.h
index 0c125d0..d0fe96c 100644
--- a/block_int.h
+++ b/block_int.h
@@ -155,6 +155,7 @@ struct BlockDriverState {
     int encrypted; /* if true, the media is encrypted */
     int valid_key; /* if true, a valid encryption key has been set */
     int sg;        /* if true, the device is a /dev/sg* */
+    int stream;    /* if true, stream from the backing file */
     /* event callback when inserting/removing */
     void (*change_cb)(void *opaque, int reason);
     void *change_opaque;
diff --git a/blockdev.c b/blockdev.c
index 99c0726..5d6cb2b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -678,6 +678,15 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
         goto err;
     }
 
+    if (bdrv_stream_enabled(dinfo->bdrv)) {
+        const char *device_name = bdrv_get_device_name(dinfo->bdrv);
+
+        if (!stream_start(device_name, 0, false, NULL, NULL)) {
+            fprintf(stderr, "qemu: warning: stream_start failed for '%s'\n",
+                    device_name);
+        }
+    }
+
     if (bdrv_key_required(dinfo->bdrv))
         autostart = 0;
     return dinfo;
-- 
1.7.4.4