Blame SOURCES/kvm-block-add-backing-file-option-to-block-stream.patch

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From dd7f33dff7cdf1d3481936560a1a1db285856eeb Mon Sep 17 00:00:00 2001
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From: Jeffrey Cody <jcody@redhat.com>
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Date: Fri, 19 Sep 2014 03:18:58 +0200
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Subject: [PATCH 3/4] block: add backing-file option to block-stream
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Message-id: <5b8611fab581db6b4c5eb31c998378090819268d.1411096194.git.jcody@redhat.com>
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Patchwork-id: 61312
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O-Subject: [PATCH qemu-kvm-rhev RHEL7.0.z 3/4] block: add backing-file option to block-stream
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Bugzilla: 1122925
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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On some image chains, QEMU may not always be able to resolve the
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filenames properly, when updating the backing file of an image
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after a block job.
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For instance, certain relative pathnames may fail, or drives may
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have been specified originally by file descriptor (e.g. /dev/fd/???),
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or a relative protocol pathname may have been used.
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In these instances, QEMU may lack the information to be able to make
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the correct choice, but the user or management layer most likely does
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have that knowledge.
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With this extension to the block-stream api, the user is able to change
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the backing file of the active layer as part of the block-stream
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operation.
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This allows the change to be 'safe', in the sense that if the attempt
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to write the active image metadata fails, then the block-stream
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operation returns failure, without disrupting the guest.
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If a backing file string is not specified in the command, the backing
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file string to use is determined in the same manner as it was
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previously.
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 13d8cc515dfcf5574077f964332d34890c0101d0)
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Conflicts:
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	block/stream.c
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	blockdev.c
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	qapi/block-core.json
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RHEL7 Notes:  Conflicts due to: surrounding context differences, and
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                                and the qapi json not being split into
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                                separate files like upstream.  Also
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                                upstream used 1024 for local backing
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                                file string size, and downstream we
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                                already use PATH_MAX instead.
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block/stream.c   |   11 +++++------
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 blockdev.c       |   23 +++++++++++++++++++----
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 hmp.c            |    2 +-
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 qapi-schema.json |   19 +++++++++++++++++--
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 qmp-commands.hx  |    2 +-
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 5 files changed, 43 insertions(+), 14 deletions(-)
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diff --git a/block/stream.c b/block/stream.c
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index 2a6f533..367120d 100644
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--- a/block/stream.c
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+++ b/block/stream.c
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@@ -32,7 +32,7 @@ typedef struct StreamBlockJob {
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     RateLimit limit;
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     BlockDriverState *base;
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     BlockdevOnError on_error;
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-    char backing_file_id[PATH_MAX];
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+    char *backing_file_str;
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 } StreamBlockJob;
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 static int coroutine_fn stream_populate(BlockDriverState *bs,
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@@ -182,7 +182,7 @@ wait:
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     if (!block_job_is_cancelled(&s->common) && sector_num == end && ret == 0) {
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         const char *base_id = NULL, *base_fmt = NULL;
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         if (base) {
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-            base_id = s->backing_file_id;
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+            base_id = s->backing_file_str;
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             if (base->drv) {
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                 base_fmt = base->drv->format_name;
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             }
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@@ -192,6 +192,7 @@ wait:
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     }
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     qemu_vfree(buf);
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+    g_free(s->backing_file_str);
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     block_job_completed(&s->common, ret);
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 }
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@@ -213,7 +214,7 @@ static const BlockJobDriver stream_job_driver = {
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 };
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 void stream_start(BlockDriverState *bs, BlockDriverState *base,
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-                  const char *base_id, int64_t speed,
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+                  const char *backing_file_str, int64_t speed,
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                   BlockdevOnError on_error,
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                   BlockDriverCompletionFunc *cb,
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                   void *opaque, Error **errp)
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@@ -233,9 +234,7 @@ void stream_start(BlockDriverState *bs, BlockDriverState *base,
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     }
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     s->base = base;
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-    if (base_id) {
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-        pstrcpy(s->backing_file_id, sizeof(s->backing_file_id), base_id);
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-    }
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+    s->backing_file_str = g_strdup(backing_file_str);
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     s->on_error = on_error;
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     s->common.co = qemu_coroutine_create(stream_run);
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diff --git a/blockdev.c b/blockdev.c
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index b22b42e..c4fb129 100644
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--- a/blockdev.c
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+++ b/blockdev.c
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@@ -1425,14 +1425,17 @@ static void block_job_cb(void *opaque, int ret)
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     bdrv_put_ref_bh_schedule(bs);
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 }
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-void qmp_block_stream(const char *device, bool has_base,
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-                      const char *base, bool has_speed, int64_t speed,
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+void qmp_block_stream(const char *device,
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+                      bool has_base, const char *base,
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+                      bool has_backing_file, const char *backing_file,
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+                      bool has_speed, int64_t speed,
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                       bool has_on_error, BlockdevOnError on_error,
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                       Error **errp)
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 {
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     BlockDriverState *bs;
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     BlockDriverState *base_bs = NULL;
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     Error *local_err = NULL;
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+    const char *base_name = NULL;
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     if (!has_on_error) {
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         on_error = BLOCKDEV_ON_ERROR_REPORT;
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@@ -1444,15 +1447,27 @@ void qmp_block_stream(const char *device, bool has_base,
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         return;
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     }
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-    if (base) {
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+    if (has_base) {
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         base_bs = bdrv_find_backing_image(bs, base);
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         if (base_bs == NULL) {
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             error_set(errp, QERR_BASE_NOT_FOUND, base);
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             return;
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         }
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+        base_name = base;
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     }
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-    stream_start(bs, base_bs, base, has_speed ? speed : 0,
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+    /* if we are streaming the entire chain, the result will have no backing
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+     * file, and specifying one is therefore an error */
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+    if (base_bs == NULL && has_backing_file) {
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+        error_setg(errp, "backing file specified, but streaming the "
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+                         "entire chain");
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+        return;
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+    }
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+
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+    /* backing_file string overrides base bs filename */
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+    base_name = has_backing_file ? backing_file : base_name;
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+
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+    stream_start(bs, base_bs, base_name, has_speed ? speed : 0,
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                  on_error, block_job_cb, bs, &local_err);
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     if (error_is_set(&local_err)) {
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         error_propagate(errp, local_err);
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diff --git a/hmp.c b/hmp.c
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index 841929d..b723b26 100644
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--- a/hmp.c
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+++ b/hmp.c
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@@ -1046,7 +1046,7 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
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     const char *base = qdict_get_try_str(qdict, "base");
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     int64_t speed = qdict_get_try_int(qdict, "speed", 0);
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-    qmp_block_stream(device, base != NULL, base,
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+    qmp_block_stream(device, base != NULL, base, false, NULL,
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                      qdict_haskey(qdict, "speed"), speed,
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                      BLOCKDEV_ON_ERROR_REPORT, true, &error);
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diff --git a/qapi-schema.json b/qapi-schema.json
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index 100b059..e11b641 100644
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--- a/qapi-schema.json
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+++ b/qapi-schema.json
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@@ -2274,6 +2274,21 @@
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 #
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 # @base:   #optional the common backing file name
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 #
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+# @backing-file: #optional The backing file string to write into the active
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+#                          layer. This filename is not validated.
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+#
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+#                          If a pathname string is such that it cannot be
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+#                          resolved by QEMU, that means that subsequent QMP or
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+#                          HMP commands must use node-names for the image in
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+#                          question, as filename lookup methods will fail.
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+#
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+#                          If not specified, QEMU will automatically determine
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+#                          the backing file string to use, or error out if there
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+#                          is no obvious choice.  Care should be taken when
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+#                          specifying the string, to specify a valid filename or
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+#                          protocol.
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+#                          (Since 2.1)
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+#
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 # @speed:  #optional the maximum speed, in bytes per second
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 #
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 # @on-error: #optional the action to take on an error (default report).
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@@ -2286,8 +2301,8 @@
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 # Since: 1.1
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 ##
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 { 'command': 'block-stream',
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-  'data': { 'device': 'str', '*base': 'str', '*speed': 'int',
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-            '*on-error': 'BlockdevOnError' } }
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+  'data': { 'device': 'str', '*base': 'str', '*backing-file': 'str',
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+            '*speed': 'int', '*on-error': 'BlockdevOnError' } }
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 #_end-rhev-only
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 ##
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diff --git a/qmp-commands.hx b/qmp-commands.hx
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index 79006c5..94f8671 100644
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--- a/qmp-commands.hx
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+++ b/qmp-commands.hx
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@@ -999,7 +999,7 @@ EQMP
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 #ifdef CONFIG_LIVE_BLOCK_OPS
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     {
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         .name       = "block-stream",
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-        .args_type  = "device:B,base:s?,speed:o?,on-error:s?",
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+        .args_type  = "device:B,base:s?,speed:o?,backing-file:s?,on-error:s?",
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         .mhandler.cmd_new = qmp_marshal_input_block_stream,
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     },
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-- 
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1.7.1
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