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2dcbb11b39
Allow a client to request a subset of negotiated meta contexts. For example, a client may ask to use a single connection to learn about both block status and dirty bitmaps, but where the dirty bitmap queries only need to be performed on a subset of the disk; forcing the server to compute that information on block status queries in the rest of the disk is wasted effort (both at the server, and on the amount of traffic sent over the wire to be parsed and ignored by the client). Qemu as an NBD client never requests to use more than one meta context, so it has no need to use block status payloads. Testing this instead requires support from libnbd, which CAN access multiple meta contexts in parallel from a single NBD connection; an interop test submitted to the libnbd project at the same time as this patch demonstrates the feature working, as well as testing some corner cases (for example, when the payload length is longer than the export length), although other corner cases (like passing the same id duplicated) requires a protocol fuzzer because libnbd is not wired up to break the protocol that badly. This also includes tweaks to 'qemu-nbd --list' to show when a server is advertising the capability, and to the testsuite to reflect the addition to that output. Of note: qemu will always advertise the new feature bit during NBD_OPT_INFO if extended headers have alreay been negotiated (regardless of whether any NBD_OPT_SET_META_CONTEXT negotiation has occurred); but for NBD_OPT_GO, qemu only advertises the feature if block status is also enabled (that is, if the client does not negotiate any contexts, then NBD_CMD_BLOCK_STATUS cannot be used, so the feature is not advertised). Signed-off-by: Eric Blake <eblake@redhat.com> Message-ID: <20230925192229.3186470-26-eblake@redhat.com> [eblake: fix logic to reject unnegotiated contexts] Signed-off-by: Eric Blake <eblake@redhat.com>
33 lines
1.8 KiB
Text
33 lines
1.8 KiB
Text
QA output created by nbd-qemu-allocation
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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, "present": true, "zero": false, "data": true, "compressed": false, "offset": 327680},
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{ "start": 1048576, "length": 2097152, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": 327680},
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{ "start": 3145728, "length": 1048576, "depth": 1, "present": false, "zero": true, "data": false, "compressed": false}]
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exports available: 1
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export: ''
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size: 4194304
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flags: 0x148f ( readonly flush fua df cache block-status-payload )
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min block: 1
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opt block: 4096
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max block: 33554432
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transaction size: 64-bit
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available meta contexts: 2
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base:allocation
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qemu:allocation-depth
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[{ "start": 0, "length": 3145728, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": OFFSET},
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{ "start": 3145728, "length": 1048576, "depth": 0, "present": true, "zero": true, "data": false, "compressed": false, "offset": OFFSET}]
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[{ "start": 0, "length": 1048576, "depth": 0, "present": true, "zero": true, "data": true, "compressed": false, "offset": OFFSET},
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{ "start": 1048576, "length": 2097152, "depth": 0, "present": false, "zero": false, "data": false, "compressed": false},
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{ "start": 3145728, "length": 1048576, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": OFFSET}]
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*** done
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