Re: [Qemu-devel] [PATCH v2 8/9] qmp: Add support of "dirty-bitmap" sync mode for drive-backup

["Benoît Canet" <benoit.canet@irqsave.net>]

The Wednesday 12 Mar 2014 à 14:31:03 (+0800), Fam Zheng wrote :
> For "dirty-bitmap" sync mode, the block job will iterate through the
> given dirty bitmap to decide if a sector needs backup (backup all the
> dirty clusters and skip clean ones), just as allocation conditions of
> "top" sync mode.
> 
> There are two bitmap use modes for sync=dirty-bitmap:
> 
>  - reset: backup job makes a copy of bitmap and resets the original
>    one.
>  - consume: back job makes the original anonymous (invisible to user)
s/back job/backup job/ ? 

>    and releases it after use.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block/backup.c            | 51 ++++++++++++++++++++++++++++++++++++++++++++++-
>  block/mirror.c            |  4 ++++
>  blockdev.c                |  9 ++++++++-
>  hmp.c                     |  4 +++-
>  include/block/block_int.h |  3 +++
>  qapi-schema.json          | 30 ++++++++++++++++++++++++----
>  qmp-commands.hx           |  7 ++++---
>  7 files changed, 98 insertions(+), 10 deletions(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index 15a2e55..6b05429 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -37,6 +37,8 @@ typedef struct CowRequest {
>  typedef struct BackupBlockJob {
>      BlockJob common;
>      BlockDriverState *target;
> +    BdrvDirtyBitmap *sync_bitmap;
> +    int sync_bitmap_gran;

Maybe a comment would help.
Reading this variable name for the first time I wonder what the _gran suffix mean.

>      MirrorSyncMode sync_mode;
>      RateLimit limit;
>      BlockdevOnError on_source_error;
> @@ -263,7 +265,7 @@ static void coroutine_fn backup_run(void *opaque)
>              job->common.busy = true;
>          }
>      } else {
> -        /* Both FULL and TOP SYNC_MODE's require copying.. */
> +        /* FULL, TOP and DIRTY_BITMAP SYNC_MODE's require copying.. */
>          for (; start < end; start++) {
>              bool error_is_read;
>  
> @@ -317,7 +319,21 @@ static void coroutine_fn backup_run(void *opaque)
>                  if (alloced == 0) {
>                      continue;
>                  }
> +            } else if (job->sync_mode == MIRROR_SYNC_MODE_DIRTY_BITMAP) {
> +                int i, dirty = 0;
> +                for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;
> +                     i += job->sync_bitmap_gran) {

Ok it's _gran for _granularity.

> +                    if (bdrv_get_dirty(bs, job->sync_bitmap,
> +                            start * BACKUP_SECTORS_PER_CLUSTER + i)) {
> +                        dirty = 1;
> +                        break;
> +                    }
> +                }
> +                if (!dirty) {
> +                    continue;
> +                }
>              }
> +
>              /* FULL sync mode we copy the whole drive. */
>              ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER,
>                      BACKUP_SECTORS_PER_CLUSTER, &error_is_read);
> @@ -341,6 +357,9 @@ static void coroutine_fn backup_run(void *opaque)
>      qemu_co_rwlock_wrlock(&job->flush_rwlock);
>      qemu_co_rwlock_unlock(&job->flush_rwlock);
>  
> +    if (job->sync_bitmap) {
> +        bdrv_release_dirty_bitmap(bs, job->sync_bitmap);
> +    }
>      hbitmap_free(job->bitmap);
>  
>      bdrv_iostatus_disable(target);
> @@ -351,12 +370,15 @@ static void coroutine_fn backup_run(void *opaque)
>  
>  void backup_start(BlockDriverState *bs, BlockDriverState *target,
>                    int64_t speed, MirrorSyncMode sync_mode,
> +                  BdrvDirtyBitmap *sync_bitmap,
> +                  BitmapUseMode bitmap_mode,
>                    BlockdevOnError on_source_error,
>                    BlockdevOnError on_target_error,
>                    BlockDriverCompletionFunc *cb, void *opaque,
>                    Error **errp)
>  {
>      int64_t len;
> +    BdrvDirtyBitmap *original;
>  
>      assert(bs);
>      assert(target);
> @@ -369,6 +391,28 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
>          return;
>      }
>  
> +    if (sync_mode == MIRROR_SYNC_MODE_DIRTY_BITMAP && !sync_bitmap) {
> +        error_setg(errp, "must provide a valid bitmap name for \"dirty-bitmap\""
> +                         "sync mode");
> +        return;
> +    }
> +
> +    if (sync_bitmap) {
> +        switch (bitmap_mode) {
> +        case BITMAP_USE_MODE_RESET:
> +            original = sync_bitmap;
> +            sync_bitmap = bdrv_copy_dirty_bitmap(bs, sync_bitmap, NULL);
> +            bdrv_reset_dirty_bitmap(bs, original);
> +            break;
> +        case BITMAP_USE_MODE_CONSUME:
> +            bdrv_dirty_bitmap_make_anon(bs, sync_bitmap);
> +            break;
> +        default:
> +            assert(0);
> +        }
> +        bdrv_disable_dirty_bitmap(bs, sync_bitmap);
> +    }
> +
>      len = bdrv_getlength(bs);
>      if (len < 0) {
>          error_setg_errno(errp, -len, "unable to get length for '%s'",
> @@ -386,6 +430,11 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
>      job->on_target_error = on_target_error;
>      job->target = target;
>      job->sync_mode = sync_mode;
> +    job->sync_bitmap = sync_bitmap;
> +    if (sync_bitmap) {
> +        job->sync_bitmap_gran =
> +            bdrv_dirty_bitmap_granularity(bs, job->sync_bitmap);
> +    }
>      job->common.len = len;
>      job->common.co = qemu_coroutine_create(backup_run);
>      qemu_coroutine_enter(job->common.co, job);
> diff --git a/block/mirror.c b/block/mirror.c
> index be8b2a1..6e4f3f3 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -615,6 +615,10 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
>      bool is_none_mode;
>      BlockDriverState *base;
>  
> +    if (mode == MIRROR_SYNC_MODE_DIRTY_BITMAP) {
> +        error_setg(errp, "Sync mode 'dirty-bitmap' not supported");
> +        return;
> +    }
>      is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
>      base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL;
>      mirror_start_job(bs, target, speed, granularity, buf_size,
> diff --git a/blockdev.c b/blockdev.c
> index aa3ee55..4120dee 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1384,6 +1384,8 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
>                       backup->sync,
>                       backup->has_mode, backup->mode,
>                       backup->has_speed, backup->speed,
> +                     backup->has_bitmap, backup->bitmap,
> +                     backup->has_bitmap_use_mode, backup->bitmap_use_mode,
>                       backup->has_on_source_error, backup->on_source_error,
>                       backup->has_on_target_error, backup->on_target_error,
>                       &local_err);
> @@ -2032,6 +2034,8 @@ void qmp_drive_backup(const char *device, const char *target,
>                        enum MirrorSyncMode sync,
>                        bool has_mode, enum NewImageMode mode,
>                        bool has_speed, int64_t speed,
> +                      bool has_bitmap, const char *bitmap,
> +                      bool has_bitmap_use_mode, enum BitmapUseMode bitmap_mode,
>                        bool has_on_source_error, BlockdevOnError on_source_error,
>                        bool has_on_target_error, BlockdevOnError on_target_error,
>                        Error **errp)
> @@ -2129,7 +2133,10 @@ void qmp_drive_backup(const char *device, const char *target,
>          return;
>      }
>  
> -    backup_start(bs, target_bs, speed, sync, on_source_error, on_target_error,
> +    backup_start(bs, target_bs, speed, sync,
> +                 has_bitmap ? bdrv_find_dirty_bitmap(bs, bitmap) : NULL,
> +                 has_bitmap_use_mode ? bitmap_mode : BITMAP_USE_MODE_RESET,
> +                 on_source_error, on_target_error,
>                   block_job_cb, bs, &local_err);
>      if (local_err != NULL) {
>          bdrv_unref(target_bs);
> diff --git a/hmp.c b/hmp.c
> index 2f279c4..2c84377 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -950,7 +950,9 @@ void hmp_drive_backup(Monitor *mon, const QDict *qdict)
>  
>      qmp_drive_backup(device, filename, !!format, format,
>                       full ? MIRROR_SYNC_MODE_FULL : MIRROR_SYNC_MODE_TOP,
> -                     true, mode, false, 0, false, 0, false, 0, &errp);
> +                     true, mode, false, 0, false, NULL,
> +                     false, 0,
> +                     false, 0, false, 0, &errp);
>      hmp_handle_error(mon, &errp);
>  }
>  
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 0bcf1c9..d02c090 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -484,6 +484,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
>   * @target: Block device to write to.
>   * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
>   * @sync_mode: What parts of the disk image should be copied to the destination.
> + * @sync_bitmap: The dirty bitmap if sync_mode is MIRROR_SYNC_MODE_DIRTY_BITMAP.
>   * @on_source_error: The action to take upon error reading from the source.
>   * @on_target_error: The action to take upon error writing to the target.
>   * @cb: Completion function for the job.
> @@ -494,6 +495,8 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
>   */
>  void backup_start(BlockDriverState *bs, BlockDriverState *target,
>                    int64_t speed, MirrorSyncMode sync_mode,
> +                  BdrvDirtyBitmap *sync_bitmap,
> +                  BitmapUseMode bitmap_mode,
>                    BlockdevOnError on_source_error,
>                    BlockdevOnError on_target_error,
>                    BlockDriverCompletionFunc *cb, void *opaque,
> diff --git a/qapi-schema.json b/qapi-schema.json
> index f8cd6b8..e4e66cb 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -1503,7 +1503,7 @@
>  # Since: 1.3
>  ##
>  { 'enum': 'MirrorSyncMode',
> -  'data': ['top', 'full', 'none'] }
> +  'data': ['top', 'full', 'none', 'dirty-bitmap'] }
>  
>  ##
>  # @BlockJobType:
> @@ -1879,6 +1879,22 @@
>    'data': { 'device': 'str', 'name': 'str' } }
>  
>  ##
> +# @BitmapUseMode
> +#
> +# An enumeration that tells QEMU what operation to take when consuming a bitmap
> +# a new image file.
> +#
> +# @consume: QEMU should just consume the bitmap and release it after using
> +#
> +# @reset: QEMU should keep an internal copy of the bitmap and reset the
> +#         dirty record from original one
> +#
> +# Since: 2.1
> +##
> +{ 'enum': 'BitmapUseMode',
> +  'data': [ 'consume', 'reset' ] }
> +
> +##
>  # @DriveBackup
>  #
>  # @device: the name of the device which should be copied.
> @@ -1891,14 +1907,19 @@
>  #          probe if @mode is 'existing', else the format of the source
>  #
>  # @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).
> +#        (all the disk, only the sectors allocated in the topmost image, from a
> +#        dirty bitmap, or only new I/O).
>  #
>  # @mode: #optional whether and how QEMU should create a new image, default is
>  #        'absolute-paths'.
>  #
>  # @speed: #optional the maximum speed, in bytes per second
>  #
> +# @bitmap: #optional the name of dirty bitmap if sync is "dirty-bitmap"
(Since 2.1)

> +#
> +# @bitmap-use-mode: #optional which operation to take when consuming @bitmap,
> +#                   default is reset. (Since 2.1)
> +#
>  # @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).
> @@ -1916,7 +1937,8 @@
>  { 'type': 'DriveBackup',
>    'data': { 'device': 'str', 'target': 'str', '*format': 'str',
>              'sync': 'MirrorSyncMode', '*mode': 'NewImageMode',
> -            '*speed': 'int',
> +            '*speed': 'int', '*bitmap': 'str',
> +            '*bitmap-use-mode': 'BitmapUseMode',
>              '*on-source-error': 'BlockdevOnError',
>              '*on-target-error': 'BlockdevOnError' } }
>  
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 205343b..4d8271a 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -1031,7 +1031,7 @@ EQMP
>      {
>          .name       = "drive-backup",
>          .args_type  = "sync:s,device:B,target:s,speed:i?,mode:s?,format:s?,"
> -                      "on-source-error:s?,on-target-error:s?",
> +                      "bitmap:s?,on-source-error:s?,on-target-error:s?",
>          .mhandler.cmd_new = qmp_marshal_input_drive_backup,
>      },
>  
> @@ -1058,8 +1058,9 @@ Arguments:
>              (json-string, optional)
>  - "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).
> +  allocated in the topmost image, "dirty-bitmap" for only sync the dirty
> +  sectors in the bitmap, or "none" to only replicate new I/O (MirrorSyncMode).
> +- "bitmap": bitmap name to use for sync==dirty-bitmap
>  - "mode": whether and how QEMU should create a new image
>            (NewImageMode, optional, default 'absolute-paths')
>  - "speed": the maximum speed, in bytes per second (json-int, optional)
> -- 
> 1.9.0
> 
>