[Qemu-devel] [PATCH 2/3] block: Add QMP support for streaming to an intermediate layer

[Alberto Garcia <berto@igalia.com>]

This adds the 'top' parameter to the 'block-stream' QMP command and
checks that its value is valid before passing it to stream_start().

Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 blockdev.c                | 19 +++++++++++++++----
 hmp.c                     |  2 +-
 include/qapi/qmp/qerror.h |  3 +++
 qapi/block-core.json      | 18 ++++++++++++++----
 qmp-commands.hx           |  2 +-
 5 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 06628ca..2404f89 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2099,6 +2099,7 @@ static void block_job_cb(void *opaque, int ret)
 
 void qmp_block_stream(const char *device,
                       bool has_base, const char *base,
+                      bool has_top, const char *top,
                       bool has_backing_file, const char *backing_file,
                       bool has_speed, int64_t speed,
                       bool has_on_error, BlockdevOnError on_error,
@@ -2106,6 +2107,7 @@ void qmp_block_stream(const char *device,
 {
     BlockDriverState *bs;
     BlockDriverState *base_bs = NULL;
+    BlockDriverState *top_bs;
     AioContext *aio_context;
     Error *local_err = NULL;
     const char *base_name = NULL;
@@ -2114,7 +2116,7 @@ void qmp_block_stream(const char *device,
         on_error = BLOCKDEV_ON_ERROR_REPORT;
     }
 
-    bs = bdrv_find(device);
+    top_bs = bs = bdrv_find(device);
     if (!bs) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
         return;
@@ -2123,12 +2125,21 @@ void qmp_block_stream(const char *device,
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_STREAM, errp)) {
+    if (has_top) {
+        top_bs = bdrv_find_backing_image(bs, top);
+        if (top_bs == NULL) {
+            error_set(errp, QERR_TOP_NOT_FOUND, top);
+            goto out;
+        }
+        assert(bdrv_get_aio_context(top_bs) == aio_context);
+    }
+
+    if (bdrv_op_is_blocked(top_bs, BLOCK_OP_TYPE_STREAM, errp)) {
         goto out;
     }
 
     if (has_base) {
-        base_bs = bdrv_find_backing_image(bs, base);
+        base_bs = bdrv_find_backing_image(top_bs, base);
         if (base_bs == NULL) {
             error_set(errp, QERR_BASE_NOT_FOUND, base);
             goto out;
@@ -2148,7 +2159,7 @@ void qmp_block_stream(const char *device,
     /* backing_file string overrides base bs filename */
     base_name = has_backing_file ? backing_file : base_name;
 
-    stream_start(bs, NULL, base_bs, base_name, has_speed ? speed : 0,
+    stream_start(bs, top_bs, base_bs, base_name, has_speed ? speed : 0,
                  on_error, block_job_cb, bs, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
diff --git a/hmp.c b/hmp.c
index b47f331..28f7adb 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1239,7 +1239,7 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
     const char *base = qdict_get_try_str(qdict, "base");
     int64_t speed = qdict_get_try_int(qdict, "speed", 0);
 
-    qmp_block_stream(device, base != NULL, base, false, NULL,
+    qmp_block_stream(device, base != NULL, base, false, NULL, false, NULL,
                      qdict_haskey(qdict, "speed"), speed,
                      true, BLOCKDEV_ON_ERROR_REPORT, &error);
 
diff --git a/include/qapi/qmp/qerror.h b/include/qapi/qmp/qerror.h
index 986260f..d075f78 100644
--- a/include/qapi/qmp/qerror.h
+++ b/include/qapi/qmp/qerror.h
@@ -127,6 +127,9 @@ void qerror_report_err(Error *err);
 #define QERR_SET_PASSWD_FAILED \
     ERROR_CLASS_GENERIC_ERROR, "Could not set password"
 
+#define QERR_TOP_NOT_FOUND \
+    ERROR_CLASS_GENERIC_ERROR, "Top '%s' not found"
+
 #define QERR_UNDEFINED_ERROR \
     ERROR_CLASS_GENERIC_ERROR, "An undefined error has occurred"
 
diff --git a/qapi/block-core.json b/qapi/block-core.json
index a3fdaf0..3073be6 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1013,6 +1013,9 @@
 # with query-block-jobs.  The operation can be stopped before it has completed
 # using the block-job-cancel command.
 #
+# Data is copied to the top image, which defaults to the active layer if no other
+# file is selected.
+#
 # If a base file is specified then sectors are not copied from that base file and
 # its backing chain.  When streaming completes the image file will have the base
 # file as its backing file.  This can be used to stream a subset of the backing
@@ -1025,8 +1028,14 @@
 #
 # @base:   #optional the common backing file name
 #
-# @backing-file: #optional The backing file string to write into the active
-#                          layer. This filename is not validated.
+# @top:    #optional Top image, only sectors below this image are streamed
+#                    into it.
+#
+#                    If not specified, the top image is the active layer.
+#                    (Since 2.3)
+#
+# @backing-file: #optional The backing file string to write into the top
+#                          image. This filename is not validated.
 #
 #                          If a pathname string is such that it cannot be
 #                          resolved by QEMU, that means that subsequent QMP or
@@ -1052,8 +1061,9 @@
 # Since: 1.1
 ##
 { 'command': 'block-stream',
-  'data': { 'device': 'str', '*base': 'str', '*backing-file': 'str',
-            '*speed': 'int', '*on-error': 'BlockdevOnError' } }
+  'data': { 'device': 'str', '*base': 'str', '*top': 'str',
+            '*backing-file': 'str', '*speed': 'int',
+            '*on-error': 'BlockdevOnError' } }
 
 ##
 # @block-job-set-speed:
diff --git a/qmp-commands.hx b/qmp-commands.hx
index a85d847..a02f19f 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -978,7 +978,7 @@ EQMP
 
     {
         .name       = "block-stream",
-        .args_type  = "device:B,base:s?,speed:o?,backing-file:s?,on-error:s?",
+        .args_type  = "device:B,base:s?,top:s?,speed:o?,backing-file:s?,on-error:s?",
         .mhandler.cmd_new = qmp_marshal_input_block_stream,
     },
 
-- 
2.1.4