qemu/qapi
Eric Blake 8417e1378c qemu-img: Make unallocated part of backing chain obvious in map
The recently-added NBD context qemu:allocation-depth is able to
distinguish between locally-present data (even when that data is
sparse) [shown as depth 1 over NBD], and data that could not be found
anywhere in the backing chain [shown as depth 0]; and the libnbd
project was recently patched to give the human-readable name "absent"
to an allocation-depth of 0.  But qemu-img map --output=json predates
that addition, and has the unfortunate behavior that all portions of
the backing chain that resolve without finding a hit in any backing
layer report the same depth as the final backing layer.  This makes it
harder to reconstruct a qcow2 backing chain using just 'qemu-img map'
output, especially when using "backing":null to artificially limit a
backing chain, because it is impossible to distinguish between a
QCOW2_CLUSTER_UNALLOCATED (which defers to a [missing] backing file)
and a QCOW2_CLUSTER_ZERO_PLAIN cluster (which would override any
backing file), since both types of clusters otherwise show as
"data":false,"zero":true" (but note that we can distinguish a
QCOW2_CLUSTER_ZERO_ALLOCATED, which would also have an "offset":
listing).

The task of reconstructing a qcow2 chain was made harder in commit
0da9856851 (nbd: server: Report holes for raw images), because prior
to that point, it was possible to abuse NBD's block status command to
see which portions of a qcow2 file resulted in BDRV_BLOCK_ALLOCATED
(showing up as NBD_STATE_ZERO in isolation) vs. missing from the chain
(showing up as NBD_STATE_ZERO|NBD_STATE_HOLE); but now qemu reports
more accurate sparseness information over NBD.

An obvious solution is to make 'qemu-img map --output=json' add an
additional "present":false designation to any cluster lacking an
allocation anywhere in the chain, without any change to the "depth"
parameter to avoid breaking existing clients.  The iotests have
several examples where this distinction demonstrates the additional
accuracy.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210701190655.2131223-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: fix more iotest fallout]
Signed-off-by: Eric Blake <eblake@redhat.com>
2021-07-12 11:10:53 -05:00
..
acpi.json qapi: Extract ACPI commands to 'acpi.json' 2020-09-29 15:41:36 +02:00
audio.json sdlaudio: add -audiodev sdl,out.buffer-count option 2021-01-15 11:25:22 +01:00
authz.json qapi/qom: Add ObjectOptions for authz-* 2021-03-19 10:17:13 +01:00
block-core.json qemu-img: Make unallocated part of backing chain obvious in map 2021-07-12 11:10:53 -05:00
block-export.json export/fuse: Add allow-other option 2021-07-09 12:26:05 +02:00
block.json qapi: Normalize version references x.y.0 to just x.y 2020-12-10 17:16:44 +01:00
char.json ui/vdagent: add clipboard support 2021-05-21 09:42:44 +02:00
common.json qapi/qom: Add ObjectOptions for input-* 2021-03-19 10:17:14 +01:00
compat.json qapi: New -compat deprecated-input=crash 2021-03-19 16:05:11 +01:00
control.json monitor: remove 'query-events' QMP command 2021-03-18 09:22:55 +00:00
crypto.json qapi/qom: Add ObjectOptions for tls-*, deprecate 'loaded' 2021-03-19 10:17:13 +01:00
dump.json schemas: Add vim modeline 2020-08-03 08:28:08 +02:00
error.json schemas: Add vim modeline 2020-08-03 08:28:08 +02:00
introspect.json monitor: Drop query-qmp-schema 'gen': false hack 2021-03-19 16:05:09 +01:00
job.json migration: introduce snapshot-{save, load, delete} QMP commands 2021-02-08 11:19:52 +00:00
machine-target.json qapi: Normalize version references x.y.0 to just x.y 2020-12-10 17:16:44 +01:00
machine.json machine: pass QAPI struct to mc->smp_parse 2021-06-25 16:16:11 +02:00
meson.build Revert "hmp: Use QAPI NetdevInfo in hmp_info_network" 2021-04-08 17:33:59 +08:00
migration.json migration/dirtyrate: make sample page count configurable 2021-06-08 20:18:25 +01:00
misc-target.json target/i386/sev: add support to query the attestation report 2021-06-01 09:32:23 -04:00
misc.json qmp: remove deprecated "change" command 2021-01-23 15:55:07 -05:00
net.json netdev: add more commands to preconfig mode 2021-06-11 10:30:13 +08:00
opts-visitor.c qapi, qemu-options: make all parsing visitors parse boolean options the same 2020-11-04 12:00:40 -05:00
pci.json qapi: Normalize version references x.y.0 to just x.y 2020-12-10 17:16:44 +01:00
pragma.json block: Remove monitor command block_passwd 2021-03-23 22:31:56 +01:00
qapi-clone-visitor.c qapi: Make visitor functions taking Error ** return bool, not void 2020-07-10 15:18:08 +02:00
qapi-dealloc-visitor.c qapi: Make visitor functions taking Error ** return bool, not void 2020-07-10 15:18:08 +02:00
qapi-schema.json qemu-options: New -compat to set policy for deprecated interfaces 2021-03-19 15:43:33 +01:00
qapi-util.c qapi, qemu-options: make all parsing visitors parse boolean options the same 2020-11-04 12:00:40 -05:00
qapi-visit-core.c qapi: Implement deprecated-input=reject for QMP command arguments 2021-03-19 16:05:11 +01:00
qdev.json qapi: Normalize version references x.y.0 to just x.y 2020-12-10 17:16:44 +01:00
qmp-dispatch.c qapi: New -compat deprecated-input=crash 2021-03-19 16:05:11 +01:00
qmp-event.c Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
qmp-registry.c qga: return a more explicit error on why a command is disabled 2021-03-16 20:21:47 -05:00
qobject-input-visitor.c qapi: New -compat deprecated-input=crash 2021-03-19 16:05:11 +01:00
qobject-output-visitor.c qapi: Implement deprecated-output=hide for QMP command results 2021-03-19 15:43:33 +01:00
qom.json hostmem: Wire up RAM_NORESERVE via "reserve" property 2021-06-15 20:27:38 +02:00
rdma.json schemas: Add vim modeline 2020-08-03 08:28:08 +02:00
replay.json replay: implement replay-seek command 2020-10-06 08:34:49 +02:00
rocker.json schemas: Add vim modeline 2020-08-03 08:28:08 +02:00
run-state.json runstate: cleanup reboot and panic actions 2021-01-21 13:00:41 +01:00
sockets.json sockets: Support multipath TCP 2021-06-08 19:36:22 +01:00
string-input-visitor.c qapi, qemu-options: make all parsing visitors parse boolean options the same 2020-11-04 12:00:40 -05:00
string-output-visitor.c string-output-visitor: Fix to use sufficient precision 2020-12-19 10:37:16 +01:00
tpm.json tpm: Return QMP error when TPM is disabled in build 2021-06-15 10:59:02 -04:00
trace-events docs: fix references to docs/devel/tracing.rst 2021-06-02 06:51:09 +02:00
trace.h trace: switch position of headers to what Meson requires 2020-08-21 06:18:24 -04:00
trace.json qapi: Add blank lines before bulleted lists 2020-02-15 11:41:50 +01:00
transaction.json block: Drop the sheepdog block driver 2021-05-12 17:42:23 +02:00
ui.json ui: Make the DisplayType enum entries conditional 2021-06-23 14:42:30 +02:00
yank.json Introduce yank feature 2021-01-13 10:21:17 +01:00