Re: [PATCH v10 2/9] copy-on-read: add filter append/drop functions

[Vladimir Sementsov-Ogievskiy]

29.09.2020 15:38, Andrey Shinkevich wrote:
> Provide API for the COR-filter insertion/removal.
> Also, drop the filter child permissions for an inactive state when the
> filter node is being removed.
>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   block/copy-on-read.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   block/copy-on-read.h | 35 ++++++++++++++++++++++
>   2 files changed, 119 insertions(+)
>   create mode 100644 block/copy-on-read.h
>
> diff --git a/block/copy-on-read.c b/block/copy-on-read.c
> index cb03e0f..3c8231f 100644
> --- a/block/copy-on-read.c
> +++ b/block/copy-on-read.c
> @@ -23,11 +23,21 @@
>   #include "qemu/osdep.h"
>   #include "block/block_int.h"
>   #include "qemu/module.h"
> +#include "qapi/error.h"
> +#include "qapi/qmp/qdict.h"
> +#include "block/copy-on-read.h"
> +
> +
> +typedef struct BDRVStateCOR {
> +    bool active;
> +} BDRVStateCOR;
>   
>   
>   static int cor_open(BlockDriverState *bs, QDict *options, int flags,
>                       Error **errp)
>   {
> +    BDRVStateCOR *state = bs->opaque;
> +
>       bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
>                                  BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
>                                  false, errp);
> @@ -42,6 +52,13 @@ static int cor_open(BlockDriverState *bs, QDict *options, 
> int flags,
>           ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
>               bs->file->bs->supported_zero_flags);
>   
> +    state->active = true;
> +
> +    /*
> +     * We don't need to call bdrv_child_refresh_perms() now as the permissions
> +     * will be updated later when the filter node gets its parent.
> +     */
> +
>       return 0;
>   }
>   
> @@ -57,6 +74,17 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
>                              uint64_t perm, uint64_t shared,
>                              uint64_t *nperm, uint64_t *nshared)
>   {
> +    BDRVStateCOR *s = bs->opaque;
> +
> +    if (!s->active) {
> +        /*
> +         * While the filter is being removed
> +         */
> +        *nperm = 0;
> +        *nshared = BLK_PERM_ALL;
> +        return;
> +    }
> +
>       *nperm = perm & PERM_PASSTHROUGH;
>       *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
>   
> @@ -135,6 +163,7 @@ static void cor_lock_medium(BlockDriverState *bs, bool locked)
>   
>   static BlockDriver bdrv_copy_on_read = {
>       .format_name                        = "copy-on-read",
> +    .instance_size                      = sizeof(BDRVStateCOR),
>   
>       .bdrv_open                          = cor_open,
>       .bdrv_child_perm                    = cor_child_perm,
> @@ -159,4 +188,59 @@ static void bdrv_copy_on_read_init(void)
>       bdrv_register(&bdrv_copy_on_read);
>   }
>   
> +
> +BlockDriverState *bdrv_cor_filter_append(BlockDriverState *bs,
> +                                         QDict *node_options,
> +                                         int flags, Error **errp)


Ok, now function can add ~any filter, not only COR.. But it's a pair for 
bdrv_cor_filter_drop(), and with "active" hack we don't want make the functions 
generic I think. So it's OK for now to keep function here and named _cor_.

> +{
> +    BlockDriverState *cor_filter_bs;
> +    Error *local_err = NULL;
> +
> +    cor_filter_bs = bdrv_open(NULL, NULL, node_options, flags, errp);
> +    if (cor_filter_bs == NULL) {
> +        error_prepend(errp, "Could not create COR-filter node: ");
> +        return NULL;
> +    }

You've dropped setting ->implicit field if filter_node_name not specified. 
Probably caller now can do it.. I don't really care about implicit case, so it's 
OK for me if it works with iotests.

So,

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>


--
Best regards,
Vladimir