Re: [Qemu-devel] [PATCH alt 1/7] block: Add status callback to bdrv_amend_options()

[Max Reitz]

On 31.07.2014 09:51, Benoît Canet wrote:
The Saturday 26 Jul 2014 à 21:22:05 (+0200), Max Reitz wrote :
Depending on the changed options and the image format,
bdrv_amend_options() may take a significant amount of time. In these
cases, a way to be informed about the operation's status is desirable.

Since the operation is rather complex and may fundamentally change the
image, implementing it as AIO or a couroutine does not seem feasible. On
the other hand, implementing it as a block job would be significantly
more difficult than a simple callback and would not add benefits other
than progress report to the amending operation, because it should not
actually be run as a block job at all.

A callback may not be very pretty, but it's very easy to implement and
perfectly fits its purpose here.

Signed-off-by: Max Reitz <mre...@redhat.com>
---
  block.c                   | 5 +++--
  block/qcow2.c             | 5 ++++-
  include/block/block.h     | 5 ++++-
  include/block/block_int.h | 3 ++-
  qemu-img.c                | 2 +-
  5 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index 3e252a2..4c8d4d8 100644
--- a/block.c
+++ b/block.c
@@ -5708,12 +5708,13 @@ void bdrv_add_before_write_notifier(BlockDriverState 
*bs,
      notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
  }
  
-int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts)
+int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
+                       BlockDriverAmendStatusCB *status_cb)
  {
      if (!bs->drv->bdrv_amend_options) {
          return -ENOTSUP;
      }
-    return bs->drv->bdrv_amend_options(bs, opts);
+    return bs->drv->bdrv_amend_options(bs, opts, status_cb);
  }
  
  /* This function will be called by the bdrv_recurse_is_first_non_filter method
diff --git a/block/qcow2.c b/block/qcow2.c
index b0faa69..757f890 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2210,7 +2210,8 @@ static int qcow2_downgrade(BlockDriverState *bs, int 
target_version)
      return 0;
  }
  
-static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
+static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
+                               BlockDriverAmendStatusCB *status_cb)
  {
      BDRVQcowState *s = bs->opaque;
      int old_version = s->qcow_version, new_version = old_version;
@@ -2223,6 +2224,8 @@ static int qcow2_amend_options(BlockDriverState *bs, 
QemuOpts *opts)
      int ret;
      QemuOptDesc *desc = opts->list->desc;
  
+    (void)status_cb;
This look like a temporary hack to please the compiler.
Am I right ? Should be comment this ?

It's removed in one of the next patches anyway; but I'll add a comment 
in v2.

Max

+
      while (desc && desc->name) {
          if (!qemu_opt_find(opts, desc->name)) {
              /* only change explicitly defined options */
diff --git a/include/block/block.h b/include/block/block.h
index 32d3676..f2b1799 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -309,7 +309,10 @@ typedef enum {
  
  int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix);
  
-int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts);
+typedef void BlockDriverAmendStatusCB(BlockDriverState *bs, int64_t offset,
+                                      int64_t total_work_size);
+int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts,
+                       BlockDriverAmendStatusCB *status_cb);
  
  /* external snapshots */
  bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f6c3bef..5c5798d 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -228,7 +228,8 @@ struct BlockDriver {
      int (*bdrv_check)(BlockDriverState* bs, BdrvCheckResult *result,
          BdrvCheckMode fix);
  
-    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts);
+    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts,
+                              BlockDriverAmendStatusCB *status_cb);
  
      void (*bdrv_debug_event)(BlockDriverState *bs, BlkDebugEvent event);
  
diff --git a/qemu-img.c b/qemu-img.c
index ef74ae4..90d6b79 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2827,7 +2827,7 @@ static int img_amend(int argc, char **argv)
          goto out;
      }
  
-    ret = bdrv_amend_options(bs, opts);
+    ret = bdrv_amend_options(bs, opts, NULL);
      if (ret < 0) {
          error_report("Error while amending options: %s", strerror(-ret));
          goto out;
--
2.0.3