diff options
| author | Eric Blake <eblake@redhat.com> | 2020-10-27 00:05:55 -0500 |
|---|---|---|
| committer | Eric Blake <eblake@redhat.com> | 2020-10-30 15:22:00 -0500 |
| commit | dbc7b01492371e4a54b92d2b6d968f9b863cc794 (patch) | |
| tree | 24812091f95b86d03192a23bec70e21d9a5b74eb /qapi/block-core.json | |
| parent | 71719cd57fc02ddfd91a4a3ca3f469bfb4d221bc (diff) | |
nbd: Add 'qemu-nbd -A' to expose allocation depth
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 block-export-add.
qemu as client is hacked into viewing the key aspects of this new
context by abusing the already-experimental x-dirty-bitmap option to
collapse all depths greater than 2, which results in a tri-state value
visible in the output of 'qemu-img map --output=json' (yes, that means
x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like
renaming it as it would introduce a needless break of back-compat,
even though we make no compat guarantees with x- members):
unallocated (depth 0) => "zero":false, "data":true
local (depth 1) => "zero":false, "data":false
backing (depth 2+) => "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 <eblake@redhat.com>
Message-Id: <20201027050556.269064-11-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Diffstat (limited to 'qapi/block-core.json')
| -rw-r--r-- | qapi/block-core.json | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/qapi/block-core.json b/qapi/block-core.json index e00fc27b5e..1b8b4156b4 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3905,9 +3905,12 @@ # # @tls-creds: TLS credentials ID # -# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of +# @x-dirty-bitmap: A metadata context 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 |