Re: [Qemu-devel] [PATCH v5 3/6] The discard flag for block stream operation

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Andrey Shinkevich (andrey.shinkevich@virtuozzo.com) wrote:
> Adding a parameter to QMP block-stream command to allow discarding
> blocks in the backing chain while blocks are being copied to the
> active layer.
> 
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>  block/copy-on-read.c      | 24 ++++++++++++++++++++++++
>  block/stream.c            |  3 +--
>  blockdev.c                |  8 +++++++-
>  hmp-commands.hx           |  4 ++--
>  hmp.c                     |  4 +++-
>  include/block/block_int.h |  2 +-
>  qapi/block-core.json      |  5 ++++-
>  7 files changed, 42 insertions(+), 8 deletions(-)
> 
> diff --git a/block/copy-on-read.c b/block/copy-on-read.c
> index 64dcc42..bf7580e 100644
> --- a/block/copy-on-read.c
> +++ b/block/copy-on-read.c
> @@ -22,11 +22,22 @@
>  
>  #include "qemu/osdep.h"
>  #include "block/block_int.h"
> +#include "qapi/qmp/qdict.h"
> +
> +typedef struct BDRVCORState {
> +    bool discard;
> +} BDRVCORState;
>  
>  
>  static int cor_open(BlockDriverState *bs, QDict *options, int flags,
>                      Error **errp)
>  {
> +    if (qdict_haskey(options, "driver.discard")) {
> +        BDRVCORState *s = bs->opaque;
> +        s->discard = qdict_get_bool(options, "driver.discard");
> +        qdict_del(options, "driver.discard");
> +    }
> +
>      bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false,
>                                 errp);
>      if (!bs->file) {
> @@ -66,6 +77,11 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
>               (c->perm & PERM_UNCHANGED);
>      *nshared = (shared & PERM_PASSTHROUGH) |
>                 (c->shared_perm & PERM_UNCHANGED);
> +
> +    BDRVCORState *s = bs->opaque;
> +    if (s->discard) {
> +        *nshared |= BLK_PERM_WRITE;
> +    }
>  }
>  
>  
> @@ -134,8 +150,15 @@ static bool cor_recurse_is_first_non_filter(BlockDriverState *bs,
>  }
>  
>  
> +static int cor_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
> +{
> +    return bdrv_get_info(bs->file->bs, bdi);
> +}
> +
> +
>  BlockDriver bdrv_copy_on_read = {
>      .format_name                        = "copy-on-read",
> +    .instance_size                      = sizeof(BDRVCORState),
>  
>      .bdrv_open                          = cor_open,
>      .bdrv_child_perm                    = cor_child_perm,
> @@ -148,6 +171,7 @@ BlockDriver bdrv_copy_on_read = {
>      .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
>      .bdrv_co_pdiscard                   = cor_co_pdiscard,
>  
> +    .bdrv_get_info                      = cor_get_info,
>      .bdrv_eject                         = cor_eject,
>      .bdrv_lock_medium                   = cor_lock_medium,
>  
> diff --git a/block/stream.c b/block/stream.c
> index af2eebf..b160eee 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -465,13 +465,12 @@ static const BlockJobDriver stream_job_driver = {
>  
>  void stream_start(const char *job_id, BlockDriverState *bs,
>                    BlockDriverState *base, const char *backing_file_str,
> -                  int creation_flags, int64_t speed,
> +                  int creation_flags, int64_t speed, bool discard,
>                    BlockdevOnError on_error, Error **errp)
>  {
>      StreamBlockJob *s;
>      BlockDriverState *iter;
>      bool bs_read_only;
> -    const bool discard = false;
>      int node_shared_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
>      int ret;
>  
> diff --git a/blockdev.c b/blockdev.c
> index a6f71f9..6a53cb7 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -3138,6 +3138,7 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>                        bool has_base_node, const char *base_node,
>                        bool has_backing_file, const char *backing_file,
>                        bool has_speed, int64_t speed,
> +                      bool has_discard, bool discard,
>                        bool has_on_error, BlockdevOnError on_error,
>                        bool has_auto_finalize, bool auto_finalize,
>                        bool has_auto_dismiss, bool auto_dismiss,
> @@ -3154,6 +3155,10 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>          on_error = BLOCKDEV_ON_ERROR_REPORT;
>      }
>  
> +    if (!has_discard) {
> +        discard = false;
> +    }
> +
>      bs = bdrv_lookup_bs(device, device, errp);
>      if (!bs) {
>          return;
> @@ -3218,7 +3223,8 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
>      }
>  
>      stream_start(has_job_id ? job_id : NULL, bs, base_bs, base_name,
> -                 job_flags, has_speed ? speed : 0, on_error, &local_err);
> +                 job_flags, has_speed ? speed : 0,
> +                 discard, on_error, &local_err);
>      if (local_err) {
>          error_propagate(errp, local_err);
>          goto out;
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index ba71558..12806db 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -95,8 +95,8 @@ ETEXI
>  
>      {
>          .name       = "block_stream",
> -        .args_type  = "device:B,speed:o?,base:s?",
> -        .params     = "device [speed [base]]",
> +        .args_type  = "device:B,speed:o?,base:s?,discard:-d",
> +        .params     = "device [speed [base]] [-d]",
>          .help       = "copy data from a backing file into a block device",
>          .cmd        = hmp_block_stream,
>      },
> diff --git a/hmp.c b/hmp.c
> index 80aa5ab..353a164 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -1923,9 +1923,11 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
>      const char *device = qdict_get_str(qdict, "device");
>      const char *base = qdict_get_try_str(qdict, "base");
>      int64_t speed = qdict_get_try_int(qdict, "speed", 0);
> +    bool discard = qdict_get_try_bool(qdict, "discard", false);
>  
>      qmp_block_stream(true, device, device, base != NULL, base, false, NULL,
> -                     false, NULL, qdict_haskey(qdict, "speed"), speed, true,
> +                     false, NULL, qdict_haskey(qdict, "speed"), speed,
> +                     true, discard, true,
>                       BLOCKDEV_ON_ERROR_REPORT, false, false, false, false,
>                       &error);

Yes, I think that's fine from the HMP side (that line is 'true' for
has_discard, discard, true for has_on_error which is the true that you
moved from the end of the previous line).


Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


>  
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index f605622..2660336 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -970,7 +970,7 @@ int is_windows_drive(const char *filename);
>   */
>  void stream_start(const char *job_id, BlockDriverState *bs,
>                    BlockDriverState *base, const char *backing_file_str,
> -                  int creation_flags, int64_t speed,
> +                  int creation_flags, int64_t speed, bool discard,
>                    BlockdevOnError on_error, Error **errp);
>  
>  /**
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 762000f..5005c57 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2337,6 +2337,9 @@
>  #
>  # @speed:  the maximum speed, in bytes per second
>  #
> +# @discard: true to delete blocks duplicated in old backing files.
> +#           (default: false). Since 4.0.
> +#
>  # @on-error: the action to take on an error (default report).
>  #            'stop' and 'enospc' can only be used if the block device
>  #            supports io-status (see BlockInfo).  Since 1.3.
> @@ -2369,7 +2372,7 @@
>  { 'command': 'block-stream',
>    'data': { '*job-id': 'str', 'device': 'str', '*base': 'str',
>              '*base-node': 'str', '*backing-file': 'str', '*speed': 'int',
> -            '*on-error': 'BlockdevOnError',
> +            '*discard': 'bool', '*on-error': 'BlockdevOnError',
>              '*auto-finalize': 'bool', '*auto-dismiss': 'bool' } }
>  
>  ##
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK