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Re: [PATCH v2 20/36] block: add bdrv_attach_child_common() transaction a
From: |
Kevin Wolf |
Subject: |
Re: [PATCH v2 20/36] block: add bdrv_attach_child_common() transaction action |
Date: |
Wed, 3 Feb 2021 22:01:04 +0100 |
Am 27.11.2020 um 15:45 hat Vladimir Sementsov-Ogievskiy geschrieben:
> Split out no-perm part of bdrv_root_attach_child() into separate
> transaction action. bdrv_root_attach_child() now moves to new
> permission update paradigm: first update graph relations then update
> permissions.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> block.c | 162 ++++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 117 insertions(+), 45 deletions(-)
>
> diff --git a/block.c b/block.c
> index f0fcd75555..a7ccbb4fb1 100644
> --- a/block.c
> +++ b/block.c
> @@ -86,6 +86,13 @@ static void bdrv_parent_set_aio_context_ignore(BdrvChild
> *c, AioContext *ctx,
> GSList **ignore);
> static void bdrv_replace_child_noperm(BdrvChild *child,
> BlockDriverState *new_bs);
> +static int bdrv_attach_child_common(BlockDriverState *child_bs,
> + const char *child_name,
> + const BdrvChildClass *child_class,
> + BdrvChildRole child_role,
> + uint64_t perm, uint64_t shared_perm,
> + void *opaque, BdrvChild **child,
> + GSList **tran, Error **errp);
If you added the new code above bdrv_root_attach_child(), we wouldn't
need the forward declaration and the patch would probably be simpler to
read (because it's the first part of bdrv_root_attach_child() that is
factored out).
> static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
> BlockReopenQueue
> *queue, Error **errp);
> @@ -2898,55 +2905,22 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState
> *child_bs,
> uint64_t perm, uint64_t shared_perm,
> void *opaque, Error **errp)
> {
> - BdrvChild *child;
> - Error *local_err = NULL;
> int ret;
> - AioContext *ctx;
> + BdrvChild *child = NULL;
> + GSList *tran = NULL;
>
> - ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL,
> errp);
> + ret = bdrv_attach_child_common(child_bs, child_name, child_class,
> + child_role, perm, shared_perm, opaque,
> + &child, &tran, errp);
> if (ret < 0) {
> - bdrv_abort_perm_update(child_bs);
> bdrv_unref(child_bs);
> return NULL;
> }
>
> - child = g_new(BdrvChild, 1);
> - *child = (BdrvChild) {
> - .bs = NULL,
> - .name = g_strdup(child_name),
> - .klass = child_class,
> - .role = child_role,
> - .perm = perm,
> - .shared_perm = shared_perm,
> - .opaque = opaque,
> - };
> -
> - ctx = bdrv_child_get_parent_aio_context(child);
> -
> - /* If the AioContexts don't match, first try to move the subtree of
> - * child_bs into the AioContext of the new parent. If this doesn't work,
> - * try moving the parent into the AioContext of child_bs instead. */
> - if (bdrv_get_aio_context(child_bs) != ctx) {
> - ret = bdrv_try_set_aio_context(child_bs, ctx, &local_err);
> - if (ret < 0) {
> - if (bdrv_parent_try_set_aio_context(child, ctx, NULL) == 0) {
> - ret = 0;
> - error_free(local_err);
> - local_err = NULL;
> - }
> - }
> - if (ret < 0) {
> - error_propagate(errp, local_err);
> - g_free(child);
> - bdrv_abort_perm_update(child_bs);
> - bdrv_unref(child_bs);
> - return NULL;
> - }
> - }
> -
> - /* This performs the matching bdrv_set_perm() for the above check. */
> - bdrv_replace_child(child, child_bs);
> + ret = bdrv_refresh_perms(child_bs, errp);
> + tran_finalize(tran, ret);
>
> + bdrv_unref(child_bs);
> return child;
> }
>
> @@ -2988,16 +2962,114 @@ BdrvChild *bdrv_attach_child(BlockDriverState
> *parent_bs,
> return child;
> }
>
> -static void bdrv_detach_child(BdrvChild *child)
> +static void bdrv_remove_empty_child(BdrvChild *child)
> {
> + assert(!child->bs);
> QLIST_SAFE_REMOVE(child, next);
> -
> - bdrv_replace_child(child, NULL);
> -
> g_free(child->name);
> g_free(child);
> }
>
> +typedef struct BdrvAttachChildCommonState {
> + BdrvChild **child;
> + AioContext *old_parent_ctx;
> + AioContext *old_child_ctx;
> +} BdrvAttachChildCommonState;
> +
> +static void bdrv_attach_child_common_abort(void *opaque)
> +{
> + BdrvAttachChildCommonState *s = opaque;
> + BdrvChild *child = *s->child;
> + BlockDriverState *bs = child->bs;
> +
> + bdrv_replace_child_noperm(child, NULL);
> +
> + if (bdrv_get_aio_context(bs) != s->old_child_ctx) {
> + bdrv_try_set_aio_context(bs, s->old_child_ctx, &error_abort);
Would failure actually be fatal? I think we can ignore it, the node is
in an AioContext that works for it.
> + }
> +
> + if (bdrv_child_get_parent_aio_context(child) != s->old_parent_ctx) {
> + bdrv_parent_try_set_aio_context(child, s->old_parent_ctx,
> + &error_abort);
And the same here.
> + }
> +
> + bdrv_unref(bs);
> + bdrv_remove_empty_child(child);
> + *s->child = NULL;
> +}
> +
> +static TransactionActionDrv bdrv_attach_child_common_drv = {
> + .abort = bdrv_attach_child_common_abort,
> +};
> +
> +/*
> + * Common part of attoching bdrv child to bs or to blk or to job
> + */
> +static int bdrv_attach_child_common(BlockDriverState *child_bs,
> + const char *child_name,
> + const BdrvChildClass *child_class,
> + BdrvChildRole child_role,
> + uint64_t perm, uint64_t shared_perm,
> + void *opaque, BdrvChild **child,
> + GSList **tran, Error **errp)
> +{
> + int ret;
> + BdrvChild *new_child;
> + AioContext *parent_ctx;
> + AioContext *child_ctx = bdrv_get_aio_context(child_bs);
> +
> + assert(child);
> + assert(*child == NULL);
> +
> + new_child = g_new(BdrvChild, 1);
> + *new_child = (BdrvChild) {
> + .bs = NULL,
> + .name = g_strdup(child_name),
> + .klass = child_class,
> + .role = child_role,
> + .perm = perm,
> + .shared_perm = shared_perm,
> + .opaque = opaque,
> + };
> +
> + parent_ctx = bdrv_child_get_parent_aio_context(new_child);
> + if (child_ctx != parent_ctx) {
> + ret = bdrv_try_set_aio_context(child_bs, parent_ctx, NULL);
> + if (ret < 0) {
> + /*
> + * bdrv_try_set_aio_context_tran don't need rollback after
> failure,
> + * so we don't care.
> + */
> + ret = bdrv_parent_try_set_aio_context(new_child, child_ctx,
> errp);
> + }
> + if (ret < 0) {
> + bdrv_remove_empty_child(new_child);
> + return ret;
> + }
> + }
Not sure why you decided to rewrite this block while moving it from
bdrv_root_attach_child().
We're losing the comment above it, and a possible error message is now
related to changing the context of the parent node instead of the newly
added node, which I imagine is less obvious in the general case.
> + bdrv_ref(child_bs);
> + bdrv_replace_child_noperm(new_child, child_bs);
> +
> + *child = new_child;
> +
> + BdrvAttachChildCommonState *s = g_new(BdrvAttachChildCommonState, 1);
> + *s = (BdrvAttachChildCommonState) {
> + .child = child,
> + .old_parent_ctx = parent_ctx,
> + .old_child_ctx = child_ctx,
> + };
> + tran_prepend(tran, &bdrv_attach_child_common_drv, s);
> +
> + return 0;
> +}
Kevin
- Re: [PATCH v2 20/36] block: add bdrv_attach_child_common() transaction action,
Kevin Wolf <=