Re: [Qemu-devel] [PATCH v3 1/3] qmp: Add command 'blockdev-backup'

[Fam Zheng <famz@redhat.com>]

On Wed, 12/17 10:36, Markus Armbruster wrote:
> Fam Zheng <famz@redhat.com> writes:
> 
> > Similar to drive-backup, but this command uses a device id as target
> > instead of creating/opening an image file.
> >
> > Also add blocker on target bs, since the target is also a named device
> > now.
> >
> > Add check and report error for bs == target which became possible but is
> > an illegal case with introduction of blockdev-backup.
> >
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  block/backup.c       | 28 +++++++++++++++++++++++++++
> >  blockdev.c           | 47 +++++++++++++++++++++++++++++++++++++++++++++
> >  qapi/block-core.json | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  qmp-commands.hx      | 44 ++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 173 insertions(+)
> >
> > diff --git a/block/backup.c b/block/backup.c
> > index 792e655..b944dd4 100644
> > --- a/block/backup.c
> > +++ b/block/backup.c
> > @@ -360,6 +360,7 @@ static void coroutine_fn backup_run(void *opaque)
> >      hbitmap_free(job->bitmap);
> >  
> >      bdrv_iostatus_disable(target);
> > +    bdrv_op_unblock_all(target, job->common.blocker);
> >  
> >      data = g_malloc(sizeof(*data));
> >      data->ret = ret;
> > @@ -379,6 +380,11 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
> >      assert(target);
> >      assert(cb);
> >  
> > +    if (bs == target) {
> > +        error_setg(errp, "Source and target cannot be the same");
> > +        return;
> > +    }
> > +
> >      if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
> >           on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
> >          !bdrv_iostatus_is_enabled(bs)) {
> > @@ -386,6 +392,26 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
> >          return;
> >      }
> >  
> > +    if (!bdrv_is_inserted(bs)) {
> > +        error_setg(errp, "Devie is not inserted: %s",
> 
> s/Devie/Device/

OK.

> 
> > +                   bdrv_get_device_name(bs));
> > +        return;
> > +    }
> > +
> > +    if (!bdrv_is_inserted(target)) {
> > +        error_setg(errp, "Devie is not inserted: %s",
> 
> Likewise.

OK.

> 
> > +                   bdrv_get_device_name(target));
> > +        return;
> > +    }
> > +
> > +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
> > +        return;
> > +    }
> > +
> > +    if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
> > +        return;
> > +    }
> > +
> >      len = bdrv_getlength(bs);
> >      if (len < 0) {
> >          error_setg_errno(errp, -len, "unable to get length for '%s'",
> > @@ -399,6 +425,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
> >          return;
> >      }
> >  
> > +    bdrv_op_block_all(target, job->common.blocker);
> > +
> >      job->on_source_error = on_source_error;
> >      job->on_target_error = on_target_error;
> >      job->target = target;
> > diff --git a/blockdev.c b/blockdev.c
> > index 57910b8..2e5068c 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -2156,6 +2156,8 @@ void qmp_drive_backup(const char *device, const char *target,
> >      aio_context = bdrv_get_aio_context(bs);
> >      aio_context_acquire(aio_context);
> >  
> > +    /* Although backup_run has this check too, we need to use bs->drv below, so
> > +     * do an early check redundantly. */
> >      if (!bdrv_is_inserted(bs)) {
> >          error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
> >          goto out;
> > @@ -2172,6 +2174,7 @@ void qmp_drive_backup(const char *device, const char *target,
> >          }
> >      }
> >  
> > +    /* Early check to avoid creating target */
> >      if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
> >          goto out;
> >      }
> > @@ -2239,6 +2242,50 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
> >      return bdrv_named_nodes_list();
> >  }
> >  
> > +void qmp_blockdev_backup(const char *device, const char *target,
> > +                         enum MirrorSyncMode sync,
> > +                         bool has_speed, int64_t speed,
> > +                         bool has_on_source_error,
> > +                         BlockdevOnError on_source_error,
> > +                         bool has_on_target_error,
> > +                         BlockdevOnError on_target_error,
> > +                         Error **errp)
> > +{
> > +    BlockDriverState *bs;
> > +    BlockDriverState *target_bs;
> > +    Error *local_err = NULL;
> > +
> > +    if (!has_speed) {
> > +        speed = 0;
> > +    }
> > +    if (!has_on_source_error) {
> > +        on_source_error = BLOCKDEV_ON_ERROR_REPORT;
> > +    }
> > +    if (!has_on_target_error) {
> > +        on_target_error = BLOCKDEV_ON_ERROR_REPORT;
> > +    }
> > +
> > +    bs = bdrv_find(device);
> > +    if (!bs) {
> > +        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> > +        return;
> > +    }
> > +
> > +    target_bs = bdrv_find(target);
> > +    if (!target_bs) {
> > +        error_set(errp, QERR_DEVICE_NOT_FOUND, target);
> > +        return;
> > +    }
> > +
> > +    bdrv_ref(target_bs);
> > +    backup_start(bs, target_bs, speed, sync, on_source_error, on_target_error,
> > +                 block_job_cb, bs, &local_err);
> > +    if (local_err != NULL) {
> > +        bdrv_unref(target_bs);
> > +        error_propagate(errp, local_err);
> > +    }
> > +}
> > +
> >  #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
> >  
> >  void qmp_drive_mirror(const char *device, const char *target,
> > diff --git a/qapi/block-core.json b/qapi/block-core.json
> > index 77a0cfb..bc02bd7 100644
> > --- a/qapi/block-core.json
> > +++ b/qapi/block-core.json
> > @@ -676,6 +676,41 @@
> >              '*on-target-error': 'BlockdevOnError' } }
> >  
> >  ##
> > +# @BlockdevBackup
> > +#
> > +# @device: the name of the device which should be copied.
> > +#
> > +# @target: the name of the backup target device.
> > +#
> > +# @sync: what parts of the disk image should be copied to the destination
> > +#        (all the disk, only the sectors allocated in the topmost image, or
> > +#        only new I/O).
> > +#
> > +# @speed: #optional the maximum speed, in bytes per second. The default is 0,
> > +#         for unlimited.
> > +#
> > +# @on-source-error: #optional the action to take on an error on the source,
> > +#                   default 'report'.  'stop' and 'enospc' can only be used
> > +#                   if the block device supports io-status (see BlockInfo).
> > +#
> > +# @on-target-error: #optional the action to take on an error on the target,
> > +#                   default 'report' (no limitations, since this applies to
> > +#                   a different block device than @device).
> > +#
> > +# Note that @on-source-error and @on-target-error only affect background I/O.
> > +# If an error occurs during a guest write request, the device's rerror/werror
> > +# actions will be used.
> > +#
> > +# Since: 2.3
> > +##
> > +{ 'type': 'BlockdevBackup',
> > +  'data': { 'device': 'str', 'target': 'str',
> > +            'sync': 'MirrorSyncMode',
> > +            '*speed': 'int',
> > +            '*on-source-error': 'BlockdevOnError',
> > +            '*on-target-error': 'BlockdevOnError' } }
> > +
> > +##
> >  # @blockdev-snapshot-sync
> >  #
> >  # Generates a synchronous snapshot of a block device.
> > @@ -795,6 +830,25 @@
> >  { 'command': 'drive-backup', 'data': 'DriveBackup' }
> >  
> >  ##
> > +# @blockdev-backup
> > +#
> > +# Start a point-in-time copy of a block device to a new destination.  The
> > +# status of ongoing blockdev-backup operations can be checked with
> > +# query-block-jobs where the BlockJobInfo.type field has the value 'backup'.
> > +# The operation can be stopped before it has completed using the
> > +# block-job-cancel command.
> > +#
> > +# For the arguments, see the documentation of BlockdevBackup.
> > +#
> > +# Returns: Nothing on success.
> > +#          If @device or @target is not a valid block device, DeviceNotFound.
> 
> Why do you need an error classes other than GenericError here?
> 

Because this is what other block job commands do, and I followed the style.

> > +#
> > +# Since 2.3
> > +##
> > +{ 'command': 'blockdev-backup', 'data': 'BlockdevBackup' }
> > +
> > +
> > +##
> >  # @query-named-block-nodes
> >  #
> >  # Get the named block driver list
> > diff --git a/qmp-commands.hx b/qmp-commands.hx
> > index 1abd619..518df0c 100644
> > --- a/qmp-commands.hx
> > +++ b/qmp-commands.hx
> > @@ -1094,6 +1094,50 @@ Example:
> >                                                 "sync": "full",
> >                                                 "target": "backup.img" } }
> >  <- { "return": {} }
> > +
> > +EQMP
> > +
> > +    {
> > +        .name       = "blockdev-backup",
> > +        .args_type  = "sync:s,device:B,target:B,speed:i?,"
> > +                      "on-source-error:s?,on-target-error:s?",
> > +        .mhandler.cmd_new = qmp_marshal_input_blockdev_backup,
> > +    },
> > +
> > +SQMP
> > +blockdev-backup
> > +------------
> > +
> > +The device version of drive-backup: this command takes an existing named device
> > +as backup target.
> > +
> > +Arguments:
> > +
> > +- "device": the name of the device which should be copied.
> > +            (json-string)
> > +- "target": the target of the new image. If the file exists, or if it is a
> > +            device, the existing file/device will be used as the new
> > +            destination.  If it does not exist, a new file will be created.
> > +            (json-string)
> 
> Still copied from drive-backup without change.  I don't think it's
> correct here.  Either fix it, or explain to me why I'm wrong :)

Overlooked by my eyes, will fix in v5 (I posted v4 earlier in Dec and got
comments from Max that are pending to be addressed).

Thanks for reviewing!

Fam

> 
> > +- "sync": what parts of the disk image should be copied to the destination;
> > +          possibilities include "full" for all the disk, "top" for only the
> > +          sectors allocated in the topmost image, or "none" to only replicate
> > +          new I/O (MirrorSyncMode).
> > +- "speed": the maximum speed, in bytes per second (json-int, optional)
> > +- "on-source-error": the action to take on an error on the source, default
> > +                     'report'.  'stop' and 'enospc' can only be used
> > +                     if the block device supports io-status.
> > +                     (BlockdevOnError, optional)
> > +- "on-target-error": the action to take on an error on the target, default
> > +                     'report' (no limitations, since this applies to
> > +                     a different block device than device).
> > +                     (BlockdevOnError, optional)
> > +
> > +Example:
> > +-> { "execute": "blockdev-backup", "arguments": { "device": "src-id",
> > +                                                  "target": "tgt-id" } }
> > +<- { "return": {} }
> > +
> >  EQMP
> >  
> >      {