Re: [Qemu-devel] [PATCH 3/5] block/dirty-bitmap: rework bdrv_remove_persistent_dirty_bitmap

[John Snow <jsnow@redhat.com>]

On 6/7/19 10:41 AM, Vladimir Sementsov-Ogievskiy wrote:
> 06.06.2019 21:41, John Snow wrote:
>> Allow propagating error code information from
>> bdrv_remove_persistent_dirty_bitmap as well.
>>
>> Give it an interface that matches the newly revised
>> bdrv_add_persistent_dirty_bitmap, including removing the persistent flag
>> when the operation succeeds and refusing to operate on bitmaps that are
>> not persistent.
>>
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> ---
>>   block/qcow2.h                |  6 +++---
>>   include/block/block_int.h    |  6 +++---
>>   include/block/dirty-bitmap.h |  6 +++---
>>   block/dirty-bitmap.c         | 25 ++++++++++++++++++++-----
>>   block/qcow2-bitmap.c         | 16 +++++++++-------
>>   blockdev.c                   | 15 ++++++---------
>>   6 files changed, 44 insertions(+), 30 deletions(-)
>>
>> diff --git a/block/qcow2.h b/block/qcow2.h
>> index 95d723d3c0..ce07f003f7 100644
>> --- a/block/qcow2.h
>> +++ b/block/qcow2.h
>> @@ -745,9 +745,9 @@ int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp);
>>   int qcow2_add_persistent_dirty_bitmap(BlockDriverState *bs,
>>                                         BdrvDirtyBitmap *bitmap,
>>                                         Error **errp);
>> -void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> -                                          const char *name,
>> -                                          Error **errp);
>> +int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> +                                         BdrvDirtyBitmap *bitmap,
>> +                                         Error **errp);
>>   
>>   ssize_t coroutine_fn
>>   qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size,
>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>> index 93bbb66cd0..59f8cb9c12 100644
>> --- a/include/block/block_int.h
>> +++ b/include/block/block_int.h
>> @@ -540,9 +540,9 @@ struct BlockDriver {
>>       int (*bdrv_add_persistent_dirty_bitmap)(BlockDriverState *bs,
>>                                               BdrvDirtyBitmap *bitmap,
>>                                               Error **errp);
>> -    void (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
>> -                                                const char *name,
>> -                                                Error **errp);
>> +    int (*bdrv_remove_persistent_dirty_bitmap)(BlockDriverState *bs,
>> +                                               BdrvDirtyBitmap *bitmap,
>> +                                               Error **errp);
>>   
>>       /**
>>        * Register/unregister a buffer for I/O. For example, when the driver is
>> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
>> index c37edbe05f..88a9832ddc 100644
>> --- a/include/block/dirty-bitmap.h
>> +++ b/include/block/dirty-bitmap.h
>> @@ -41,9 +41,9 @@ void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs);
>>   int bdrv_add_persistent_dirty_bitmap(BlockDriverState *bs,
>>                                         BdrvDirtyBitmap *bitmap,
>>                                         Error **errp);
>> -void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> -                                         const char *name,
>> -                                         Error **errp);
>> +int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> +                                        BdrvDirtyBitmap *bitmap,
>> +                                        Error **errp);
>>   void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap);
>>   void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap);
>>   void bdrv_enable_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap);
>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
>> index 615f8480b2..4667f9e65a 100644
>> --- a/block/dirty-bitmap.c
>> +++ b/block/dirty-bitmap.c
>> @@ -455,15 +455,30 @@ void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs)
>>    * BdrvDirtyBitmap can have .persistent = true but not yet saved and have no
>>    * stored version. For such bitmap bdrv_remove_persistent_dirty_bitmap() should
>>    * not fail.
>> - * This function doesn't release corresponding BdrvDirtyBitmap.
>> + * This function doesn't release the corresponding BdrvDirtyBitmap.
>>    */
>> -void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> -                                         const char *name,
>> -                                         Error **errp)
>> +int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> +                                        BdrvDirtyBitmap *bitmap,
>> +                                        Error **errp)
>>   {
>> +    int ret = 0;
>> +
>> +    if (!bdrv_dirty_bitmap_get_persistence(bitmap)) {
>> +        error_setg(errp, "Bitmap '%s' is not persistent, "
>> +                   "so it cannot be removed from node '%s'",
>> +                   bdrv_dirty_bitmap_name(bitmap),
>> +                   bdrv_get_device_or_node_name(bs));
>> +        return -EINVAL;
>> +    }
>> +
>>       if (bs->drv && bs->drv->bdrv_remove_persistent_dirty_bitmap) {
>> -        bs->drv->bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
>> +        ret = bs->drv->bdrv_remove_persistent_dirty_bitmap(bs, bitmap, errp);
>>       }
>> +    if (!ret) {
>> +        bdrv_dirty_bitmap_set_persistence(bitmap, false);
>> +    }
>> +
>> +    return ret;
>>   }
>>   
>>   int bdrv_add_persistent_dirty_bitmap(BlockDriverState *bs,
>> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
>> index c3a72ca782..930a6c91ff 100644
>> --- a/block/qcow2-bitmap.c
>> +++ b/block/qcow2-bitmap.c
>> @@ -1402,23 +1402,24 @@ static Qcow2Bitmap *find_bitmap_by_name(Qcow2BitmapList *bm_list,
>>       return NULL;
>>   }
>>   
>> -void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> -                                          const char *name,
>> -                                          Error **errp)
>> +int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>> +                                         BdrvDirtyBitmap *bitmap,
>> +                                         Error **errp)
>>   {
>> -    int ret;
>> +    int ret = 0;
> 
> dead assignment
> 
>>       BDRVQcow2State *s = bs->opaque;
>>       Qcow2Bitmap *bm;
>>       Qcow2BitmapList *bm_list;
>> +    const char *name = bdrv_dirty_bitmap_name(bitmap);
>>   
>>       if (s->nb_bitmaps == 0) {
>>           /* Absence of the bitmap is not an error: see explanation above
>>            * bdrv_remove_persistent_dirty_bitmap() definition. */
>> -        return;
>> +        return 0;
>>       }
>>   
>> -    if (bitmap_list_load(bs, &bm_list, errp)) {
>> -        return;
>> +    if ((ret = bitmap_list_load(bs, &bm_list, errp))) {
>> +        return ret;
>>       }
>>   
>>       bm = find_bitmap_by_name(bm_list, name);
> if (bm == NULL) {
>     goto fail;
> }
> 
> You don't set ret, as it's considered success. Worth s/fail/out then (preexisting, of course)?
> 

This becomes an error in the next patch, so I'll omit this suggestion
because the problem goes away soon anyway.

>> @@ -1439,6 +1440,7 @@ void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>>   fail:
>>       bitmap_free(bm);
>>       bitmap_list_free(bm_list);
>> +    return ret;
>>   }
>>   
>>   void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
>> diff --git a/blockdev.c b/blockdev.c
>> index 169a8da831..82f02d8e72 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -2875,7 +2875,6 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
>>   {
>>       BlockDriverState *bs;
>>       BdrvDirtyBitmap *bitmap;
>> -    Error *local_err = NULL;
> 
> Oh, that's cool. And it was my mistake to create interfaces provoking endless local_errors..
> 

I was worried these first three patches might look useless, but I'm glad
you like the idea of doing it this way.

>>       AioContext *aio_context = NULL;
>>   
>>       bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
>> @@ -2889,20 +2888,18 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
>>       }
>>   
>>       if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
>> +        int ret;
>> +
>>           aio_context = bdrv_get_aio_context(bs);
> 
> and here, could you define aio_context in this block?
> 

Indeed.

>>           aio_context_acquire(aio_context);
>> -        bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
>> -        if (local_err != NULL) {
>> -            error_propagate(errp, local_err);
>> -            goto out;
>> +        ret = bdrv_remove_persistent_dirty_bitmap(bs, bitmap, errp);
>> +        aio_context_release(aio_context);
>> +        if (ret) {
>> +            return;
>>           }
>>       }
>>   
>>       bdrv_release_dirty_bitmap(bs, bitmap);
>> - out:
>> -    if (aio_context) {
>> -        aio_context_release(aio_context);
>> -    }
>>   }
>>   
>>   /**
>>
> 
> With some my suggestions or without:
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 

Will take them, thanks for the review!