Re: [PATCH v11 02/13] copy-on-read: add filter append/drop functions
On 14.10.2020 13:44, Max Reitz wrote:
On 12.10.20 19:43, 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(a)virtuozzo.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com>
> ---
> block/copy-on-read.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> block/copy-on-read.h | 35 +++++++++++++++++++++
> 2 files changed, 123 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..bcccf0f 100644
> --- a/block/copy-on-read.c
> +++ b/block/copy-on-read.c
[...]
> @@ -159,4 +188,63 @@ 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)
I had hoped you could make this a generic block layer function. :(
(Because it really is rather generic)
*shrug*
Actually, I did (and still can do) that for the 'append node' function
only but not for the 'drop node' one so far...
diff --git a/block.c b/block.c
index 11ab55f..f41e876 100644
--- a/block.c
+++ b/block.c
@@ -4669,6 +4669,55 @@ static void bdrv_delete(BlockDriverState *bs)
g_free(bs);
}
+BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict
*node_options,
+ int flags, Error **errp)
+{
+ BlockDriverState *new_node_bs;
+ Error *local_err = NULL;
+
+ new_node_bs = bdrv_open(NULL, NULL, node_options, flags, errp);
+ if (new_node_bs == NULL) {
+ error_prepend(errp, "Could not create node: ");
+ return NULL;
+ }
+
+ bdrv_drained_begin(bs);
+ bdrv_replace_node(bs, new_node_bs, &local_err);
+ bdrv_drained_end(bs);
+
+ if (local_err) {
+ bdrv_unref(new_node_bs);
+ error_propagate(errp, local_err);
+ return NULL;
+ }
+
+ return new_node_bs;
+}
+
+void bdrv_remove_node(BlockDriverState *bs)
+{
+ BdrvChild *child;
+ BlockDriverState *inferior_bs;
+
+ child = bdrv_filter_or_cow_child(bs);
+ if (!child) {
+ return;
+ }
+ inferior_bs = child->bs;
+
+ /* Retain the BDS until we complete the graph change. */
+ bdrv_ref(inferior_bs);
+ /* Hold a guest back from writing while permissions are being reset. */
+ bdrv_drained_begin(inferior_bs);
+ /* Refresh permissions before the graph change. */
+ bdrv_child_refresh_perms(bs, child, &error_abort);
+ bdrv_replace_node(bs, inferior_bs, &error_abort);
+
+ bdrv_drained_end(inferior_bs);
+ bdrv_unref(inferior_bs);
+ bdrv_unref(bs);
+}
So, it is an intermediate solution in this patch of the series. I am
going to make both functions generic once Vladimir overhauls the QEMU
permission update system. Otherwise, the COR-filter node cannot be
removed from the backing chain gracefully.
Thank you for your r-b. If the next version comes, I can move the
'append node' function only to the generic layer.
Andrey
Reviewed-by: Max Reitz <mreitz(a)redhat.com>
> +{
> + 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;
> + }
> +
> + if (!qdict_get_try_str(node_options, "node-name")) {
> + cor_filter_bs->implicit = true;
> + }
> +
> + bdrv_drained_begin(bs);
> + bdrv_replace_node(bs, cor_filter_bs, &local_err);
> + bdrv_drained_end(bs);
> +
> + if (local_err) {
> + bdrv_unref(cor_filter_bs);
> + error_propagate(errp, local_err);
> + return NULL;
> + }
> +
> + return cor_filter_bs;
> +}