Allow the server to expose an additional metacontext to be requested
by savvy clients. qemu-nbd adds a new option -A to expose the
qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
can also be set via QMP when using nbd-server-add.
qemu as client can be hacked into viewing this new context by using
the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;
although it is worth noting the decoding of how such context
information will appear in 'qemu-img map --output=json':
NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
NBD_STATE_DEPTH_BACKING => "zero":true, "data":true
libnbd as client is probably a nicer way to get at the information
without having to decipher such hacks in qemu as client. ;)
Signed-off-by: Eric Blake
---
docs/tools/qemu-nbd.rst| 6
qapi/block-core.json | 7 ++--
include/block/nbd.h| 7 ++--
blockdev-nbd.c | 3 +-
nbd/server.c | 8 +++--
qemu-nbd.c | 16 ++---
tests/qemu-iotests/309 | 73 ++
tests/qemu-iotests/309.out | 22
tests/qemu-iotests/group | 1 +
9 files changed, 129 insertions(+), 14 deletions(-)
create mode 100755 tests/qemu-iotests/309
create mode 100644 tests/qemu-iotests/309.out
diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst
index 667861cb22e9..0e545a97cfa3 100644
--- a/docs/tools/qemu-nbd.rst
+++ b/docs/tools/qemu-nbd.rst
@@ -72,6 +72,12 @@ driver options if ``--image-opts`` is specified.
Export the disk as read-only.
+.. option:: -A, --allocation-depth
+
+ Expose allocation depth information via the
+ ``qemu:allocation-depth`` context accessible through
+ NBD_OPT_SET_META_CONTEXT.
+
.. option:: -B, --bitmap=NAME
If *filename* has a qcow2 persistent bitmap *NAME*, expose
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b3ec30a83cd7..84f7a7a34dc1 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3874,9 +3874,12 @@
#
# @tls-creds: TLS credentials ID
#
-# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of
+# @x-dirty-bitmap: A metacontext name such as "qemu:dirty-bitmap:NAME" or
+# "qemu:allocation-depth" to query in place of the
# traditional "base:allocation" block status (see
-# NBD_OPT_LIST_META_CONTEXT in the NBD protocol) (since 3.0)
+# NBD_OPT_LIST_META_CONTEXT in the NBD protocol; and
+# yes, naming this option x-context would have made
+# more sense) (since 3.0)
#
# @reconnect-delay: On an unexpected disconnect, the nbd client tries to
# connect again until succeeding or encountering a serious
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 71a2623f7842..f660e0274ce3 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -336,9 +336,10 @@ typedef struct NBDClient NBDClient;
NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
uint64_t size, const char *name, const char *desc,
- const char *bitmap, bool readonly, bool shared,
- void (*close)(NBDExport *), bool writethrough,
- BlockBackend *on_eject_blk, Error **errp);
+ bool alloc_depth, const char *bitmap, bool readonly,
+ bool shared, void (*close)(NBDExport *),
+ bool writethrough, BlockBackend *on_eject_blk,
+ Error **errp);
void nbd_export_close(NBDExport *exp);
void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
void nbd_export_get(NBDExport *exp);
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 1a95d89f0096..562ea3751b85 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -203,7 +203,8 @@ void qmp_nbd_server_add(BlockExportNbd *arg, Error **errp)
arg->writable = false;
}
-exp = nbd_export_new(bs, 0, len, arg->name, arg->description, arg->bitmap,
+exp = nbd_export_new(bs, 0, len, arg->name, arg->description,
+ arg->alloc, arg->bitmap,
!arg->writable, !arg->writable,
NULL, false, on_eject_blk, errp);
if (!exp) {
diff --git a/nbd/server.c b/nbd/server.c
index 02d5fb375b24..f5e0e115b703 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1450,9 +1450,10 @@ static void nbd_eject_notifier(Notifier *n, void *data)
NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
uint64_t size, const char *name, const char *desc,
- const char *bitmap, bool readonly, bool shared,
- void (*close)(NBDExport *), bool writethrough,
- BlockBackend *on_eject_blk, Error **errp)
+ bool alloc_depth, const
