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Re: [PATCH v10 8/9] block: remove unused backing-file name parameter


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH v10 8/9] block: remove unused backing-file name parameter
Date: Wed, 7 Oct 2020 13:21:01 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1

29.09.2020 15:38, Andrey Shinkevich wrote:
The block stream QMP parameter backing-file is in use no more. It
designates a backing file name to set in QCOW2 image header after the
block stream job finished. The base file name is used instead.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>

We can't just remove it without a deprecation period of three releases.

So actually, in a previous patch, we should implement new behavior for
automatic backing-file detection if this parameter is unspecified. Amd
keep old behavior for backing-file-name if it is given.

Hmm. Or, probably, we can use direct base for base-filename? And in cases
when we should skip filters (for example of parallel jobs) user should
specify backing-file explicitly?

---
  block/monitor/block-hmp-cmds.c |  2 +-
  block/stream.c                 |  6 +-----
  blockdev.c                     | 17 +----------------
  include/block/block_int.h      |  2 +-
  qapi/block-core.json           | 17 +----------------
  5 files changed, 5 insertions(+), 39 deletions(-)

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index 4e66775..5f19499 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -506,7 +506,7 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
      int64_t speed = qdict_get_try_int(qdict, "speed", 0);
qmp_block_stream(true, device, device, base != NULL, base, false, NULL,
-                     false, NULL, qdict_haskey(qdict, "speed"), speed, true,
+                     qdict_haskey(qdict, "speed"), speed, true,
                       BLOCKDEV_ON_ERROR_REPORT, false, NULL, false, false, 
false,
                       false, &error);
diff --git a/block/stream.c b/block/stream.c
index b0719e9..fe2663f 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -34,7 +34,6 @@ typedef struct StreamBlockJob {
      BlockDriverState *base_overlay; /* COW overlay (stream from this) */
      BlockDriverState *above_base;   /* Node directly above the base */
      BlockdevOnError on_error;
-    char *backing_file_str;
      bool bs_read_only;
      bool chain_frozen;
  } StreamBlockJob;
@@ -103,8 +102,6 @@ static void stream_clean(Job *job)
          blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
          bdrv_reopen_set_read_only(bs, true, NULL);
      }
-
-    g_free(s->backing_file_str);
  }
static int coroutine_fn stream_run(Job *job, Error **errp)
@@ -220,7 +217,7 @@ static const BlockJobDriver stream_job_driver = {
  };
void stream_start(const char *job_id, BlockDriverState *bs,
-                  BlockDriverState *base, const char *backing_file_str,
+                  BlockDriverState *base,
                    int creation_flags, int64_t speed,
                    BlockdevOnError on_error,
                    const char *filter_node_name,
@@ -295,7 +292,6 @@ void stream_start(const char *job_id, BlockDriverState *bs,
s->base_overlay = base_overlay;
      s->above_base = above_base;
-    s->backing_file_str = g_strdup(backing_file_str);
      s->bs_read_only = bs_read_only;
      s->chain_frozen = true;
diff --git a/blockdev.c b/blockdev.c
index d719c47..b223601 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2486,7 +2486,6 @@ out:
  void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
                        bool has_base, const char *base,
                        bool has_base_node, const char *base_node,
-                      bool has_backing_file, const char *backing_file,
                        bool has_speed, int64_t speed,
                        bool has_on_error, BlockdevOnError on_error,
                        bool has_filter_node_name, const char *filter_node_name,
@@ -2498,7 +2497,6 @@ void qmp_block_stream(bool has_job_id, const char 
*job_id, const char *device,
      BlockDriverState *base_bs = NULL;
      AioContext *aio_context;
      Error *local_err = NULL;
-    const char *base_name = NULL;
      int job_flags = JOB_DEFAULT;
if (!has_on_error) {
@@ -2526,7 +2524,6 @@ void qmp_block_stream(bool has_job_id, const char 
*job_id, const char *device,
              goto out;
          }
          assert(bdrv_get_aio_context(base_bs) == aio_context);
-        base_name = base;
      }
if (has_base_node) {
@@ -2541,7 +2538,6 @@ void qmp_block_stream(bool has_job_id, const char 
*job_id, const char *device,
          }
          assert(bdrv_get_aio_context(base_bs) == aio_context);
          bdrv_refresh_filename(base_bs);
-        base_name = base_bs->filename;
      }
/* Check for op blockers in the whole chain between bs and base */
@@ -2553,17 +2549,6 @@ void qmp_block_stream(bool has_job_id, const char 
*job_id, const char *device,
          }
      }
- /* if we are streaming the entire chain, the result will have no backing
-     * file, and specifying one is therefore an error */
-    if (base_bs == NULL && has_backing_file) {
-        error_setg(errp, "backing file specified, but streaming the "
-                         "entire chain");
-        goto out;
-    }
-
-    /* backing_file string overrides base bs filename */
-    base_name = has_backing_file ? backing_file : base_name;
-
      if (has_auto_finalize && !auto_finalize) {
          job_flags |= JOB_MANUAL_FINALIZE;
      }
@@ -2571,7 +2556,7 @@ void qmp_block_stream(bool has_job_id, const char 
*job_id, const char *device,
          job_flags |= JOB_MANUAL_DISMISS;
      }
- stream_start(has_job_id ? job_id : NULL, bs, base_bs, base_name,
+    stream_start(has_job_id ? job_id : NULL, bs, base_bs,
                   job_flags, has_speed ? speed : 0, on_error,
                   filter_node_name, &local_err);
      if (local_err) {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f782737..bbe2ee6 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1147,7 +1147,7 @@ int is_windows_drive(const char *filename);
   * BlockDriverState.
   */
  void stream_start(const char *job_id, BlockDriverState *bs,
-                  BlockDriverState *base, const char *backing_file_str,
+                  BlockDriverState *base,
                    int creation_flags, int64_t speed,
                    BlockdevOnError on_error,
                    const char *filter_node_name,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 32fb097..6358606 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2512,21 +2512,6 @@
  # @base-node: the node name of the backing file.
  #             It cannot be set if @base is also set. (Since 2.8)
  #
-# @backing-file: 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
-#                HMP commands must use node-names for the image in
-#                question, as filename lookup methods will fail.
-#
-#                If not specified, QEMU will automatically determine
-#                the backing file string to use, or error out if there
-#                is no obvious choice.  Care should be taken when
-#                specifying the string, to specify a valid filename or
-#                protocol.
-#                (Since 2.1)
-#
  # @speed: the maximum speed, in bytes per second
  #
  # @on-error: the action to take on an error (default report).
@@ -2566,7 +2551,7 @@
  ##
  { 'command': 'block-stream',
    'data': { '*job-id': 'str', 'device': 'str', '*base': 'str',
-            '*base-node': 'str', '*backing-file': 'str', '*speed': 'int',
+            '*base-node': 'str', '*speed': 'int',
              '*on-error': 'BlockdevOnError',
              '*filter-node-name': 'str',
              '*auto-finalize': 'bool', '*auto-dismiss': 'bool' } }



--
Best regards,
Vladimir



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