[PATCH v3 0/6] NBD 64-bit extensions (spec only)

[Eric Blake]

v2 was here:
https://lists.debian.org/nbd/2022/11/msg00030.html
The bulk of the changes since then are:
 - forbid NBD_OPT_EXPORT_NAME once extended headers are negotiated (Wouter)
 - consistently use 'maximum payload', rather than a haphazard mix of
   'maximum block payload' (Vladimir)

At this point, I want to make sure we are happy with the spec before
re-posting patches for qemu and libnbd (there were some slight tweaks
to the spec compared to v2, which will be easy enough to code, but I
want to make sure there won't be any other tweaks needed based on
review comments to this proposal).

I could still be persuaded that if extended headers are negotiated,
then the server should ONLY send back 64-bit block status replies (as
written here, and as I implemented in v2 patches for qemu and libnbd,
I specified that the server can choose either 32- or 64-bit replies,
based on what fits best, and regardless of whether the client made a
request with effect length less than 32 bits; clients must therefore
be prepared to handle both types of replies).

I'm still not sure whether patch 6 is desirable; it didn't get any
feedback in my v2 posting.

In relation to v2, the subject line for patch 2 changed (the 'git
backport-diff' tool doesn't handle that well), and the interdiff
changes look bigger than they really are due to reflowed paragraphs.

[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively

001/6:[----] [-C] 'spec: Recommend cap on NBD_REPLY_TYPE_BLOCK_STATUS length'
002/6:[down] 'spec: Change maximum block size to maximum payload size'
003/6:[0237] [FC] 'spec: Add NBD_OPT_EXTENDED_HEADERS'
004/6:[----] [-C] 'spec: Allow 64-bit block status results'
005/6:[----] [-C] 'spec: Introduce NBD_FLAG_BLOCK_STATUS_PAYLOAD'
006/6:[0062] [FC] 'RFC: spec: Introduce NBD_REPLY_TYPE_OFFSET_HOLE_EXT'

Eric Blake (6):
  spec: Recommend cap on NBD_REPLY_TYPE_BLOCK_STATUS length
  spec: Change maximum block size to maximum payload size
  spec: Add NBD_OPT_EXTENDED_HEADERS
  spec: Allow 64-bit block status results
  spec: Introduce NBD_FLAG_BLOCK_STATUS_PAYLOAD
  RFC: spec: Introduce NBD_REPLY_TYPE_OFFSET_HOLE_EXT

 doc/proto.md | 738 ++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 549 insertions(+), 189 deletions(-)


base-commit: fd2c5a60e36ef0ea0d7fd6f8a6bd908d24d5801d
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2.39.2