On Wed, 9 Sep 2020 21:59:17 +0300
Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> wrote:
> The recommended use of qemu error api assumes returning status together
> with setting errp and avoid void functions with errp parameter. Let's
> improve bdrv_append and some friends to reduce error-propagation
> overhead in further patches.
>
> Choose int return status, because bdrv_replace_node() has call to
> bdrv_check_update_perm(), which reports int status, which seems correct
> to propagate.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
Reviewed-by: Greg Kurz <gr...@kaod.org>
> include/block/block.h | 12 ++++++------
> block.c | 39 ++++++++++++++++++++++++---------------
> 2 files changed, 30 insertions(+), 21 deletions(-)
>
> diff --git a/include/block/block.h b/include/block/block.h
> index 6e36154061..03b3cee8f8 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -336,10 +336,10 @@ int bdrv_create(BlockDriver *drv, const char* filename,
> int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp);
>
> BlockDriverState *bdrv_new(void);
> -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
> - Error **errp);
> -void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> - Error **errp);
> +int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
> + Error **errp);
> +int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> + Error **errp);
>
> int bdrv_parse_aio(const char *mode, int *flags);
> int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough);
> @@ -351,8 +351,8 @@ BdrvChild *bdrv_open_child(const char *filename,
> BdrvChildRole child_role,
> bool allow_none, Error **errp);
> BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp);
> -void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
> - Error **errp);
> +int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
> + Error **errp);
> int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
> const char *bdref_key, Error **errp);
> BlockDriverState *bdrv_open(const char *filename, const char *reference,
> diff --git a/block.c b/block.c
> index 2ba76b2c36..6d35449027 100644
> --- a/block.c
> +++ b/block.c
> @@ -2866,14 +2866,15 @@ static BdrvChildRole
> bdrv_backing_role(BlockDriverState *bs)
> * Sets the backing file link of a BDS. A new reference is created; callers
> * which don't need their own reference any more must call bdrv_unref().
> */
> -void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
> +int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
> Error **errp)
> {
> + int ret = 0;
> bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
> bdrv_inherits_from_recursive(backing_hd, bs);
>
> if (bdrv_is_backing_chain_frozen(bs, backing_bs(bs), errp)) {
> - return;
> + return -EPERM;
> }
>
> if (backing_hd) {
> @@ -2891,15 +2892,22 @@ void bdrv_set_backing_hd(BlockDriverState *bs,
> BlockDriverState *backing_hd,
>
> bs->backing = bdrv_attach_child(bs, backing_hd, "backing", &child_of_bds,
> bdrv_backing_role(bs), errp);
> + if (!bs->backing) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> /* If backing_hd was already part of bs's backing chain, and
> * inherits_from pointed recursively to bs then let's update it to
> * point directly to bs (else it will become NULL). */
> - if (bs->backing && update_inherits_from) {
> + if (update_inherits_from) {
> backing_hd->inherits_from = bs;
> }
>
> out:
> bdrv_refresh_limits(bs, NULL);
> +
> + return ret;
> }
>
> /*
> @@ -4517,8 +4525,8 @@ static bool should_update_child(BdrvChild *c,
> BlockDriverState *to)
> return ret;
> }
>
> -void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> - Error **errp)
> +int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> + Error **errp)
> {
> BdrvChild *c, *next;
> GSList *list = NULL, *p;
> @@ -4540,6 +4548,7 @@ void bdrv_replace_node(BlockDriverState *from,
> BlockDriverState *to,
> continue;
> }
> if (c->frozen) {
> + ret = -EPERM;
> error_setg(errp, "Cannot change '%s' link to '%s'",
> c->name, from->node_name);
> goto out;
> @@ -4575,6 +4584,8 @@ out:
> g_slist_free(list);
> bdrv_drained_end(from);
> bdrv_unref(from);
> +
> + return ret;
> }
>
> /*
> @@ -4593,20 +4604,16 @@ out:
> * parents of bs_top after bdrv_append() returns. If the caller needs to
> keep a
> * reference of its own, it must call bdrv_ref().
> */
> -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
> - Error **errp)
> +int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
> + Error **errp)
> {
> - Error *local_err = NULL;
> -
> - bdrv_set_backing_hd(bs_new, bs_top, &local_err);
> - if (local_err) {
> - error_propagate(errp, local_err);
> + int ret = bdrv_set_backing_hd(bs_new, bs_top, errp);
> + if (ret < 0) {
> goto out;
> }
>
> - bdrv_replace_node(bs_top, bs_new, &local_err);
> - if (local_err) {
> - error_propagate(errp, local_err);
> + ret = bdrv_replace_node(bs_top, bs_new, errp);
> + if (ret < 0) {
> bdrv_set_backing_hd(bs_new, NULL, &error_abort);
> goto out;
> }
> @@ -4615,6 +4622,8 @@ void bdrv_append(BlockDriverState *bs_new,
> BlockDriverState *bs_top,
> * additional reference any more. */
> out:
> bdrv_unref(bs_new);
> +
> + return ret;
> }
>
> static void bdrv_delete(BlockDriverState *bs)
