Re: [Qemu-devel] [PATCH 2/2 v2] Add the blockdev-reopen and blockdev-migrate commands

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 24 Feb 2012 16:49:04 +0000
Federico Simoncelli <fsimonce@redhat.com> wrote:

> Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>

How does this relate to migrate -b? Should it be deprecated?

Btw, would be nice to have a 0/2 intro email describing the feature and changelog
info.

> ---
>  blockdev.c       |  107 ++++++++++++++++++++++++++++++++++++++++++++++++------
>  hmp-commands.hx  |   38 +++++++++++++++++++
>  hmp.c            |   24 ++++++++++++
>  hmp.h            |    2 +
>  qapi-schema.json |   54 +++++++++++++++++++++++++++
>  5 files changed, 213 insertions(+), 12 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 2c132a3..f51bd6f 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -646,9 +646,8 @@ void do_commit(Monitor *mon, const QDict *qdict)
>      }
>  }
>  
> -void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
> -                                bool has_format, const char *format,
> -                                Error **errp)
> +static void change_blockdev_image(const char *device, const char *new_image_file,
> +                                  const char *format, bool create, Error **errp)
>  {
>      BlockDriverState *bs;
>      BlockDriver *drv, *old_drv, *proto_drv;
> @@ -671,7 +670,7 @@ void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
>      old_drv = bs->drv;
>      flags = bs->open_flags;
>  
> -    if (!has_format) {
> +    if (!format) {
>          format = "qcow2";
>      }
>  
> @@ -681,24 +680,26 @@ void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
>          return;
>      }
>  
> -    proto_drv = bdrv_find_protocol(snapshot_file);
> +    proto_drv = bdrv_find_protocol(new_image_file);
>      if (!proto_drv) {
>          error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
>          return;
>      }
>  
> -    ret = bdrv_img_create(snapshot_file, format, bs->filename,
> -                          bs->drv->format_name, NULL, -1, flags);
> -    if (ret) {
> -        error_set(errp, QERR_UNDEFINED_ERROR);
> -        return;
> +    if (create) {
> +        ret = bdrv_img_create(new_image_file, format, bs->filename,
> +                              bs->drv->format_name, NULL, -1, flags);
> +        if (ret) {
> +            error_set(errp, QERR_UNDEFINED_ERROR);
> +            return;
> +        }
>      }
>  
>      bdrv_drain_all();
>      bdrv_flush(bs);
>  
>      bdrv_close(bs);
> -    ret = bdrv_open(bs, snapshot_file, flags, drv);
> +    ret = bdrv_open(bs, new_image_file, flags, drv);
>      /*
>       * If reopening the image file we just created fails, fall back
>       * and try to re-open the original image. If that fails too, we
> @@ -709,11 +710,93 @@ void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
>          if (ret != 0) {
>              error_set(errp, QERR_OPEN_FILE_FAILED, old_filename);
>          } else {
> -            error_set(errp, QERR_OPEN_FILE_FAILED, snapshot_file);
> +            error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
>          }
>      }
>  }
>  
> +void qmp_drive_reopen(const char *device, const char *new_image_file,
> +                         bool has_format, const char *format, Error **errp)
> +{
> +    change_blockdev_image(device, new_image_file,
> +                          has_format ? format : NULL, false, errp);
> +}
> +
> +void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
> +                                bool has_format, const char *format,
> +                                Error **errp)
> +{
> +    change_blockdev_image(device, snapshot_file,
> +                          has_format ? format : NULL, true, errp);
> +}
> +
> +static void qmp_blockdev_mirror(const char *device, const char *destination,
> +                                const char *new_image_file, Error **errp)
> +{

Minor: this is a not a qmp function, please drop the qmp_ prefix then.

> +    BlockDriver *drv;
> +    int i, j, escape;
> +    char new_filename[2048], *filename;

I'd use PATH_MAX for new_filename's size.

> +
> +    drv = bdrv_find_format("blkmirror");
> +    if (!drv) {
> +        error_set(errp, QERR_INVALID_BLOCK_FORMAT, "blkmirror");
> +        return;
> +    }
> +
> +    escape = 0;
> +    for (i = 0, j = 0; j < strlen(new_image_file); j++) {
> + loop:
> +        if (!(i < sizeof(new_filename) - 2)) {
> +            error_set(errp, QERR_INVALID_PARAMETER_VALUE,
> +                      "new-image-file", "shorter filename");
> +            return;
> +        }
> +
> +        if (new_image_file[j] == ':' || new_image_file[j] == '\\') {
> +            if (!escape) {
> +                new_filename[i++] = '\\', escape = 1;
> +                goto loop;
> +            } else {
> +                escape = 0;
> +            }
> +        }
> +
> +        new_filename[i++] = new_image_file[j];
> +    }

IMO, you could require the filename arguments to be escaped already.

> +
> +    filename = g_strdup_printf("blkmirror:%s:%s", new_filename, destination);
> +    change_blockdev_image(device, filename, "blkmirror", false, errp);
> +    g_free(filename);
> +}
> +
> +void qmp_blockdev_migrate(const char *device, bool incremental,
> +                          const char *destination, bool has_new_image_file,
> +                          const char *new_image_file, Error **errp)
> +{
> +    BlockDriverState *bs;
> +
> +    bs = bdrv_find(device);
> +    if (!bs) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> +        return;
> +    }
> +    if (bdrv_in_use(bs)) {
> +        error_set(errp, QERR_DEVICE_IN_USE, device);
> +        return;
> +    }
> +
> +    if (incremental) {
> +        if (!has_new_image_file) {
> +            error_set(errp, QERR_INVALID_PARAMETER_VALUE,
> +                      "incremental", "a new image file");
> +        } else {
> +            qmp_blockdev_mirror(device, destination, new_image_file, errp);
> +        }
> +    } else {
> +        error_set(errp, QERR_NOT_SUPPORTED);
> +    }

The command documentation says that 'incremental' and 'new_image_file' are
optionals, but the code makes them required. Why?

> +}
> +
>  static void eject_device(BlockDriverState *bs, int force, Error **errp)
>  {
>      if (bdrv_in_use(bs)) {
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 573b823..4aacf2a 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -886,6 +886,44 @@ Snapshot device, using snapshot file as target if provided
>  ETEXI
>  
>      {
> +        .name       = "drive_reopen",
> +        .args_type  = "device:B,new-image-file:s?,format:s?",
> +        .params     = "device [new-image-file] [format]",
> +        .help       = "Assigns a new image file to a device.\n\t\t\t"
> +                      "The image will be opened using the format\n\t\t\t"
> +                      "specified or 'qcow2' by default.\n\t\t\t"
> +                      "This command is deprecated.",
> +        .mhandler.cmd = hmp_drive_reopen,
> +    },
> +
> +STEXI
> +@item drive_reopen
> +@findex drive_reopen
> +Assigns a new image file to a device.
> +ETEXI
> +
> +    {
> +        .name       = "blkdev_migrate",
> +        .args_type  = "incremental:-i,device:B,destination:s,new-image-file:s?",
> +        .params     = "device mode destination [new-image-file]",
> +        .help       = "Migrates the device to a new destination.\n\t\t\t"
> +                      "If the incremental (-i) option is used then\n\t\t\t"
> +                      "only the new writes are sent to the destination.\n\t\t\t"
> +                      "This method is particularly useful if used in\n\t\t\t"
> +                      "conjunction with new-image-file (a new image for\n\t\t\t"
> +                      "the device) allowing the current image to be\n\t\t\t"
> +                      "transferred to the destination by an external\n\t\t\t"
> +                      "manager.",
> +        .mhandler.cmd = hmp_blkdev_migrate,
> +    },
> +
> +STEXI
> +@item blkdev_migrate
> +@findex blkdev_migrate
> +Migrates the device to a new destination.
> +ETEXI
> +
> +    {
>          .name       = "drive_add",
>          .args_type  = "pci_addr:s,opts:s",
>          .params     = "[[<domain>:]<bus>:]<slot>\n"
> diff --git a/hmp.c b/hmp.c
> index 8ff8c94..282d3e5 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -701,6 +701,30 @@ void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict)
>      hmp_handle_error(mon, &errp);
>  }
>  
> +void hmp_drive_reopen(Monitor *mon, const QDict *qdict)
> +{
> +    const char *device = qdict_get_str(qdict, "device");
> +    const char *filename = qdict_get_str(qdict, "new-image-file");
> +    const char *format = qdict_get_try_str(qdict, "format");
> +    Error *errp = NULL;
> +
> +    qmp_drive_reopen(device, filename, !!format, format, &errp);
> +    hmp_handle_error(mon, &errp);
> +}
> +
> +void hmp_blkdev_migrate(Monitor *mon, const QDict *qdict)
> +{
> +    bool incremental = qdict_get_try_bool(qdict, "incremental", 0);
> +    const char *device = qdict_get_str(qdict, "device");
> +    const char *destination = qdict_get_str(qdict, "destination");
> +    const char *new_image_file = qdict_get_try_str(qdict, "new-image-file");
> +    Error *errp = NULL;
> +
> +    qmp_blockdev_migrate(device, incremental, destination,
> +                         !!new_image_file, new_image_file, &errp);
> +    hmp_handle_error(mon, &errp);
> +}
> +
>  void hmp_migrate_cancel(Monitor *mon, const QDict *qdict)
>  {
>      qmp_migrate_cancel(NULL);
> diff --git a/hmp.h b/hmp.h
> index 18eecbd..3c66257 100644
> --- a/hmp.h
> +++ b/hmp.h
> @@ -47,6 +47,8 @@ void hmp_block_passwd(Monitor *mon, const QDict *qdict);
>  void hmp_balloon(Monitor *mon, const QDict *qdict);
>  void hmp_block_resize(Monitor *mon, const QDict *qdict);
>  void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict);
> +void hmp_drive_reopen(Monitor *mon, const QDict *qdict);
> +void hmp_blkdev_migrate(Monitor *mon, const QDict *qdict);
>  void hmp_migrate_cancel(Monitor *mon, const QDict *qdict);
>  void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict);
>  void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict);
> diff --git a/qapi-schema.json b/qapi-schema.json
> index d02ee86..df1248c 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -1136,6 +1136,60 @@
>    'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str' } }
>  
>  ##
> +# @drive-reopen
> +#
> +# Assigns a new image file to a device.
> +#
> +# @device: the name of the device for which we are chainging the image file.
> +#
> +# @new-image-file: the target of the new image. If the file doesn't exists the
> +#                  command will fail.
> +#
> +# @format: #optional the format of the new image, default is 'qcow2'.
> +#
> +# Returns: nothing on success
> +#          If @device is not a valid block device, DeviceNotFound
> +#          If @new-image-file can't be opened, OpenFileFailed
> +#          If @format is invalid, InvalidBlockFormat
> +#
> +# Notes: This command is deprecated.

As I said in the other thread, we need a replacement to deprecate something.

> +#
> +# Since 1.1
> +##
> +
> +{ 'command': 'drive-reopen',
> +  'data': { 'device': 'str', 'new-image-file': 'str', '*format': 'str' } }
> +
> +##
> +# @blockdev-migrate
> +#
> +# Migrates the device to a new destination.
> +#
> +# @device: the name of the block device to migrate.
> +#
> +# @incremental: if true only the new writes are sent to the destination.
> +#               This method is particularly useful if used in conjunction
> +#               with new-image-file allowing the current image to be
> +#               transferred to the destination by an external manager.
> +#
> +# @destination: the destination of the block migration.
> +#
> +# @new-image-file: #optional an existing image file that will replace
> +#                  the current one in the device.
> +#
> +# Returns: nothing on success
> +#          If @device is not a valid block device, DeviceNotFound
> +#          If @mode is not a valid migration mode, InvalidParameterValue
> +#          If @destination can't be opened, OpenFileFailed
> +#          If @new-image-file can't be opened, OpenFileFailed
> +#
> +# Since 1.1
> +##
> +{ 'command': 'blockdev-migrate',
> +  'data': { 'device': 'str', 'incremental' : 'bool',
> +            'destination': 'str', '*new-image-file': 'str' } }
> +
> +##
>  # @human-monitor-command:
>  #
>  # Execute a command on the human monitor and return the output.