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

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

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)?

> @@ -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..

>       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?

>           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>

-- 
Best regards,
Vladimir