[pve-devel] [RFC v2 qemu 01/10] block/rbd: support selected key-value-pairs via QAPI
Fiona Ebner
f.ebner at proxmox.com
Fri May 23 15:31:47 CEST 2025
Currently, most Ceph configuration options are not exposed via QAPI.
While it is possible to specify a dedicated Ceph configuration file,
specialized options are often only required for a selection of images
on the RBD storage, not all of them. To avoid the need to generate a
dedicated Ceph configuration file for each image (or for each required
combination of options), support a selection of key-value pairs via
QAPI.
Initially, this is just 'rbd_cache_policy'. For example, this is
useful with small images used as a pflash for EFI variables. Setting
the 'rbd_cache_policy' to 'writeback' yields a substantial improvement
there [0].
The function qemu_rbd_extract_key_value_pairs() was copied/adapted
from the existing qemu_rbd_extract_encryption_create_options().
[0]: https://bugzilla.proxmox.com/show_bug.cgi?id=3329#c9
Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
New in v2.
block/rbd.c | 73 ++++++++++++++++++++++++++++++++++++++++++++
qapi/block-core.json | 37 ++++++++++++++++++++++
2 files changed, 110 insertions(+)
diff --git a/block/rbd.c b/block/rbd.c
index 24e820d056..3928d8fee4 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -293,6 +293,27 @@ static int qemu_rbd_set_auth(rados_t cluster, BlockdevOptionsRbd *opts,
return 0;
}
+static int qemu_rbd_set_key_value_pairs(rados_t cluster,
+ RbdKeyValuePairs *key_value_pairs,
+ Error **errp)
+{
+ if (!key_value_pairs) {
+ return 0;
+ }
+
+ if (key_value_pairs->has_rbd_cache_policy) {
+ RbdCachePolicy value = key_value_pairs->rbd_cache_policy;
+ int r = rados_conf_set(cluster, "rbd_cache_policy",
+ RbdCachePolicy_str(value));
+ if (r < 0) {
+ error_setg_errno(errp, -r, "could not set 'rbd_cache_policy'");
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
static int qemu_rbd_set_keypairs(rados_t cluster, const char *keypairs_json,
Error **errp)
{
@@ -786,6 +807,44 @@ exit:
return ret;
}
+static int qemu_rbd_extract_key_value_pairs(
+ QemuOpts *opts,
+ RbdKeyValuePairs **key_value_pairs,
+ Error **errp)
+{
+ QDict *opts_qdict;
+ QDict *key_value_pairs_qdict;
+ Visitor *v;
+ int ret = 0;
+
+ opts_qdict = qemu_opts_to_qdict(opts, NULL);
+ qdict_extract_subqdict(opts_qdict, &key_value_pairs_qdict,
+ "key-value-pairs.");
+ qobject_unref(opts_qdict);
+ if (!qdict_size(key_value_pairs_qdict)) {
+ *key_value_pairs = NULL;
+ goto exit;
+ }
+
+ /* Convert options into a QAPI object */
+ v = qobject_input_visitor_new_flat_confused(key_value_pairs_qdict, errp);
+ if (!v) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ visit_type_RbdKeyValuePairs(v, NULL, key_value_pairs, errp);
+ visit_free(v);
+ if (!*key_value_pairs) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+exit:
+ qobject_unref(key_value_pairs_qdict);
+ return ret;
+}
+
static int coroutine_fn qemu_rbd_co_create_opts(BlockDriver *drv,
const char *filename,
QemuOpts *opts,
@@ -795,6 +854,7 @@ static int coroutine_fn qemu_rbd_co_create_opts(BlockDriver *drv,
BlockdevCreateOptionsRbd *rbd_opts;
BlockdevOptionsRbd *loc;
RbdEncryptionCreateOptions *encrypt = NULL;
+ RbdKeyValuePairs *key_value_pairs = NULL;
Error *local_err = NULL;
const char *keypairs, *password_secret;
QDict *options = NULL;
@@ -843,6 +903,13 @@ static int coroutine_fn qemu_rbd_co_create_opts(BlockDriver *drv,
loc->image = g_strdup(qdict_get_try_str(options, "image"));
keypairs = qdict_get_try_str(options, "=keyvalue-pairs");
+ /* These are the key-value pairs coming in via the QAPI. */
+ ret = qemu_rbd_extract_key_value_pairs(opts, &key_value_pairs, errp);
+ if (ret < 0) {
+ goto exit;
+ }
+ loc->key_value_pairs = key_value_pairs;
+
ret = qemu_rbd_do_create(create_options, keypairs, password_secret, errp);
if (ret < 0) {
goto exit;
@@ -932,6 +999,12 @@ static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
goto failed_shutdown;
}
+ /* For the key-value pairs coming via QAPI. */
+ r = qemu_rbd_set_key_value_pairs(*cluster, opts->key_value_pairs, errp);
+ if (r < 0) {
+ goto failed_shutdown;
+ }
+
if (mon_host) {
r = rados_conf_set(*cluster, "mon_host", mon_host);
if (r < 0) {
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 02c043f0f7..360f467f6e 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4645,6 +4645,39 @@
'data': { 'luks': 'RbdEncryptionCreateOptionsLUKS',
'luks2': 'RbdEncryptionCreateOptionsLUKS2' } }
+##
+# @RbdCachePolicy:
+#
+# An enumeration of values for the 'rbd_cache_policy' Ceph
+# configuration setting. See the Ceph documentation for details.
+#
+# @writearound: cachable writes return immediately, reads are not
+# served from the cache.
+#
+# @writeback: cachable writes return immediately, reads are served
+# from the cache.
+#
+# @writethrough: writes return only when the data is on disk for all
+# replicas, reads are served from the cache.
+#
+# Since 10.1
+##
+{ 'enum' : 'RbdCachePolicy',
+ 'data' : [ 'writearound', 'writeback', 'writethrough' ] }
+
+
+##
+# @RbdKeyValuePairs:
+#
+# Key-value pairs for Ceph configuration.
+#
+# @rbd-cache-policy: Ceph configuration option 'rbd_cache_policy'.
+#
+# Since 10.1
+##
+{ 'struct': 'RbdKeyValuePairs',
+ 'data': { '*rbd-cache-policy': 'RbdCachePolicy' } }
+
##
# @BlockdevOptionsRbd:
#
@@ -4671,6 +4704,9 @@
# authentication. This maps to Ceph configuration option "key".
# (Since 3.0)
#
+# @key-value-pairs: Key-value pairs for additional Ceph configuraton.
+# (Since 10.1)
+#
# @server: Monitor host address and port. This maps to the "mon_host"
# Ceph option.
#
@@ -4686,6 +4722,7 @@
'*user': 'str',
'*auth-client-required': ['RbdAuthMode'],
'*key-secret': 'str',
+ '*key-value-pairs' : 'RbdKeyValuePairs',
'*server': ['InetSocketAddressBase'] } }
##
--
2.39.5
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