dbc7b01492
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>
23 lines
1.2 KiB
Plaintext
23 lines
1.2 KiB
Plaintext
QA output created by 309
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=== Initial image setup ===
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Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=4194304
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wrote 2097152/2097152 bytes at offset 0
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2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4194304 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
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wrote 2097152/2097152 bytes at offset 1048576
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2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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=== Check allocation over NBD ===
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[{ "start": 0, "length": 1048576, "depth": 1, "zero": false, "data": true, "offset": 327680},
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{ "start": 1048576, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": 327680},
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{ "start": 3145728, "length": 1048576, "depth": 1, "zero": true, "data": false}]
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[{ "start": 0, "length": 3145728, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
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{ "start": 3145728, "length": 1048576, "depth": 0, "zero": true, "data": false, "offset": OFFSET}]
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[{ "start": 0, "length": 1048576, "depth": 0, "zero": true, "data": true, "offset": OFFSET},
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{ "start": 1048576, "length": 2097152, "depth": 0, "zero": false, "data": false},
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{ "start": 3145728, "length": 1048576, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
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*** done
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