Re: [Qemu-devel] [Qemu-block] [PATCH 4/5] qapi: add x-block-dirty-bitmap-merge

[John Snow <jsnow@redhat.com>]

On 06/05/2018 05:13 PM, Jeff Cody wrote:
> On Tue, Jun 05, 2018 at 02:59:04PM -0400, John Snow wrote:
>> From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> ---
>>  block/dirty-bitmap.c         | 18 ++++++++++++++++++
>>  blockdev.c                   | 30 ++++++++++++++++++++++++++++++
>>  include/block/dirty-bitmap.h |  3 ++-
>>  qapi/block-core.json         | 38 ++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 88 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
>> index 56234257f4..4159d3929e 100644
>> --- a/block/dirty-bitmap.c
>> +++ b/block/dirty-bitmap.c
>> @@ -757,3 +757,21 @@ int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t offset)
>>  {
>>      return hbitmap_next_zero(bitmap->bitmap, offset);
>>  }
>> +
>> +void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
>> +                             Error **errp)
>> +{
>> +    /* only bitmaps from one bds are supported */
>> +    assert(dest->mutex == src->mutex);
>> +
>> +    qemu_mutex_lock(dest->mutex);
>> +
>> +    assert(bdrv_dirty_bitmap_enabled(dest));
>> +    assert(!bdrv_dirty_bitmap_readonly(dest));
>> +
>> +    if (!hbitmap_merge(dest->bitmap, src->bitmap)) {
>> +        error_setg(errp, "Bitmaps are incompatible and can't be merged");
>> +    }
>> +
>> +    qemu_mutex_unlock(dest->mutex);
>> +}
>> diff --git a/blockdev.c b/blockdev.c
>> index 33bfe4817f..b00908fdfd 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -3044,6 +3044,36 @@ void qmp_x_block_dirty_bitmap_disable(const char *node, const char *name,
>>      bdrv_disable_dirty_bitmap(bitmap);
>>  }
>>  
>> +void qmp_x_block_dirty_bitmap_merge(const char *node, const char *dst_name,
>> +                                    const char *src_name, Error **errp)
>> +{
>> +    BlockDriverState *bs;
>> +    BdrvDirtyBitmap *dst, *src;
>> +
>> +    dst = block_dirty_bitmap_lookup(node, dst_name, &bs, errp);
>> +    if (!dst || !bs) {
> 
> !bs check should be dropped, as it doesn't do anything, since
> block_dirty_bitmap_lookup() cannot return a NULL BlockDriverState.
> 

Oh, makes sense.

>> +        return;
>> +    }
>> +
>> +    if (bdrv_dirty_bitmap_frozen(dst)) {
>> +        error_setg(errp, "Bitmap '%s' is frozen and cannot be modified",
>> +                   dst_name);
>> +        return;
>> +    } else if (bdrv_dirty_bitmap_readonly(dst)) {
>> +        error_setg(errp, "Bitmap '%s' is readonly and cannot be modified",
>> +                   dst_name);
>> +        return;
>> +    }
>> +
>> +    src = bdrv_find_dirty_bitmap(bs, src_name);
>> +    if (!src) {
>> +        error_setg(errp, "Dirty bitmap '%s' not found", src_name);
>> +        return;
>> +    }
>> +
>> +    bdrv_merge_dirty_bitmap(dst, src, errp);
>> +}
>> +
>>  BlockDirtyBitmapSha256 *qmp_x_debug_block_dirty_bitmap_sha256(const char *node,
>>                                                                const char *name,
>>                                                                Error **errp)
>> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
>> index 1ff8949b1b..1e14743032 100644
>> --- a/include/block/dirty-bitmap.h
>> +++ b/include/block/dirty-bitmap.h
>> @@ -70,7 +70,8 @@ void bdrv_dirty_bitmap_set_readonly(BdrvDirtyBitmap *bitmap, bool value);
>>  void bdrv_dirty_bitmap_set_persistance(BdrvDirtyBitmap *bitmap,
>>                                         bool persistent);
>>  void bdrv_dirty_bitmap_set_qmp_locked(BdrvDirtyBitmap *bitmap, bool qmp_locked);
>> -
>> +void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
>> +                             Error **errp);
>>  
>>  /* Functions that require manual locking.  */
>>  void bdrv_dirty_bitmap_lock(BdrvDirtyBitmap *bitmap);
>> diff --git a/qapi/block-core.json b/qapi/block-core.json
>> index c061884a0e..3999175c23 100644
>> --- a/qapi/block-core.json
>> +++ b/qapi/block-core.json
>> @@ -1740,6 +1740,20 @@
>>    'data': { 'node': 'str', 'name': 'str', '*granularity': 'uint32',
>>              '*persistent': 'bool', '*autoload': 'bool' } }
>>  
>> +##
>> +# @BlockDirtyBitmapMerge:
>> +#
>> +# @node: name of device/node which the bitmap is tracking
>> +#
>> +# @dst_name: name of the destination dirty bitmap
>> +#
>> +# @src_name: name of the source dirty bitmap
>> +#
>> +# Since: 3.0
>> +##
>> +{ 'struct': 'BlockDirtyBitmapMerge',
>> +  'data': { 'node': 'str', 'dst_name': 'str', 'src_name': 'str' } }
>> +
>>  ##
>>  # @block-dirty-bitmap-add:
>>  #
>> @@ -1850,6 +1864,30 @@
>>      { 'command': 'x-block-dirty-bitmap-disable',
>>        'data': 'BlockDirtyBitmap' }
>>  
>> +##
>> +# @x-block-dirty-bitmap-merge:
>> +#
>> +# Merge @src_name dirty bitmap to @dst_name dirty bitmap. @src_name dirty
>> +# bitmap is unchanged.
>> +#
> 
> Can we also extended a promise that @dst_name is unchanged on error?
> 

Absolutely we can.

>> +# Returns: nothing on success
>> +#          If @node is not a valid block device, DeviceNotFound
>> +#          If @dst_name or @src_name is not found, GenericError
>> +#          If bitmaps has different sizes or granularities, GenericError
>> +#
>> +# Since: 3.0
>> +#
>> +# Example:
>> +#
>> +# -> { "execute": "x-block-dirty-bitmap-merge",
>> +#      "arguments": { "node": "drive0", "dst_name": "bitmap0",
>> +#                     "src_name": "bitmap1" } }
>> +# <- { "return": {} }
>> +#
>> +##
>> +      { 'command': 'x-block-dirty-bitmap-merge',
>> +        'data': 'BlockDirtyBitmapMerge' }
>> +
>>  ##
>>  # @BlockDirtyBitmapSha256:
>>  #
>> -- 
>> 2.14.3
>>
>>
>