On Thu, 12/12 16:33, Benoît Canet wrote:
> Signed-off-by: Benoit Canet <ben...@irqsave.net>
> ---
> block.c | 65
> ++++++++++++++++++++++++++++++++++++++++-------
> block/blkverify.c | 2 +-
> blockdev.c | 2 +-
> include/block/block.h | 20 +++++++--------
> include/block/block_int.h | 12 ++++++---
> 5 files changed, 77 insertions(+), 24 deletions(-)
>
> diff --git a/block.c b/block.c
> index 22190a4..57946b7 100644
> --- a/block.c
> +++ b/block.c
> @@ -4992,21 +4992,68 @@ int bdrv_amend_options(BlockDriverState *bs,
> QEMUOptionParameter *options)
> return bs->drv->bdrv_amend_options(bs, options);
> }
>
> -ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *bs)
> +/* Used to recurse on single child block filters.
> + * Single child block filter will store their child in bs->file.
> + */
> +bool bdrv_generic_is_first_non_filter(BlockDriverState *bs,
> + BlockDriverState *candidate)
> {
> - if (bs->drv->bdrv_check_ext_snapshot) {
> - return bs->drv->bdrv_check_ext_snapshot(bs);
> + if (!bs->drv) {
> + return false;
> + }
> +
> + if (!bs->drv->authorizations[BS_IS_A_FILTER]) {
> + if (bs == candidate) {
> + return true;
> + } else {
> + return false;
> + }
> + }
> +
> + if (!bs->drv->authorizations[BS_FILTER_PASS_DOWN]) {
> + return false;
> }
>
> - if (bs->file && bs->file->drv && bs->file->drv->bdrv_check_ext_snapshot)
> {
> - return bs->file->drv->bdrv_check_ext_snapshot(bs);
> + if (!bs->file) {
> + return false;
> + }
> +
> + return bdrv_recurse_is_first_non_filter(bs->file, candidate);
> +}
> +
> +bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
> + BlockDriverState *candidate)
> +{
> + if (bs->drv && bs->drv->bdrv_recurse_is_first_non_filter) {
> + return bs->drv->bdrv_recurse_is_first_non_filter(bs, candidate);
> }
>
> - /* external snapshots are allowed by default */
> - return EXT_SNAPSHOT_ALLOWED;
> + return bdrv_generic_is_first_non_filter(bs, candidate);
> }
>
> -ExtSnapshotPerm bdrv_check_ext_snapshot_forbidden(BlockDriverState *bs)
> +/* This function check if the candidate is the first non filter bs down it's
s/check/checks/
> + * bs chain. Since we don't have pointers to parents it explore all bs chains
> + * from the top. Some filters can choose not to pass down the recursion.
> + */
> +bool bdrv_is_first_non_filter(BlockDriverState *candidate)
> {
> - return EXT_SNAPSHOT_FORBIDDEN;
> + BlockDriverState *bs;
> +
> + /* walk down the bs forest recursively */
> + QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
> + bool perm;
> +
> + if (!bs->file) {
> + continue;
> + }
> +
> + perm = bdrv_recurse_is_first_non_filter(bs->file, candidate);
> +
> + /* candidate is the first non filter */
> + if (perm) {
> + return true;
> + }
> + }
> +
> + return false;
> }
> diff --git a/block/blkverify.c b/block/blkverify.c
> index 3c63528..853afa9 100644
> --- a/block/blkverify.c
> +++ b/block/blkverify.c
> @@ -417,7 +417,7 @@ static BlockDriver bdrv_blkverify = {
> .bdrv_aio_writev = blkverify_aio_writev,
> .bdrv_aio_flush = blkverify_aio_flush,
>
> - .bdrv_check_ext_snapshot = bdrv_check_ext_snapshot_forbidden,
> + .authorizations = { true, false },
> };
>
> static void bdrv_blkverify_init(void)
> diff --git a/blockdev.c b/blockdev.c
> index 838df50..ebb8f48 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1236,7 +1236,7 @@ static void
> external_snapshot_prepare(BlkTransactionState *common,
> }
> }
>
> - if (bdrv_check_ext_snapshot(state->old_bs) != EXT_SNAPSHOT_ALLOWED) {
> + if (!bdrv_is_first_non_filter(state->old_bs)) {
> error_set(errp, QERR_FEATURE_DISABLED, "snapshot");
> return;
> }
> diff --git a/include/block/block.h b/include/block/block.h
> index f7d8017..16812b0 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -283,16 +283,16 @@ int bdrv_amend_options(BlockDriverState *bs_new,
> QEMUOptionParameter *options);
> /* external snapshots */
>
> typedef enum {
> - EXT_SNAPSHOT_ALLOWED,
> - EXT_SNAPSHOT_FORBIDDEN,
> -} ExtSnapshotPerm;
> -
> -/* return EXT_SNAPSHOT_ALLOWED if external snapshot is allowed
> - * return EXT_SNAPSHOT_FORBIDDEN if external snapshot is forbidden
> - */
> -ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *bs);
> -/* helper used to forbid external snapshots like in blkverify */
> -ExtSnapshotPerm bdrv_check_ext_snapshot_forbidden(BlockDriverState *bs);
> + BS_IS_A_FILTER,
> + BS_FILTER_PASS_DOWN,
> + BS_AUTHORIZATION_COUNT,
> +} BsAuthorization;
> +
> +bool bdrv_generic_is_first_non_filter(BlockDriverState *bs,
> + BlockDriverState *candidate);
> +bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
> + BlockDriverState *candidate);
> +bool bdrv_is_first_non_filter(BlockDriverState *candidate);
>
> /* async block I/O */
> typedef void BlockDriverDirtyHandler(BlockDriverState *bs, int64_t sector,
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index bd5220f..7933ecc 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -69,10 +69,16 @@ struct BlockDriver {
> const char *format_name;
> int instance_size;
>
> - /* if not defined external snapshots are allowed
> - * future block filters will query their children to build the response
> + /* this table of boolean contains authorizations for the block
> operations */
> + bool authorizations[BS_AUTHORIZATION_COUNT];
> + /* for snapshots complex block filter like Quorum can implement the
> + * following recursive callback instead of BS_IS_A_FILTER.
> + * It's purpose is to recurse on the filter children while calling
> + * bdrv_recurse_is_first_non_filter on them.
> + * For a sample implentation look in the future Quorum block filter.
s/implentation/implementation/
> */
> - ExtSnapshotPerm (*bdrv_check_ext_snapshot)(BlockDriverState *bs);
> + bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs,
> + BlockDriverState *candidate);
>
> int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char
> *filename);
> int (*bdrv_probe_device)(const char *filename);
> --
> 1.8.3.2
>
>
