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Re: [Qemu-devel] [PATCH for-3.2 v3 0/3] HMP/snapshot changes - do not us

From: Daniel Henrique Barboza
Subject: Re: [Qemu-devel] [PATCH for-3.2 v3 0/3] HMP/snapshot changes - do not use ID anymore
Date: Mon, 21 Jan 2019 07:43:04 -0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1


I believe all the discussion that happened in v2 applies here as well. Do we
have a plan for this series? Should I add something else (warning message
or doc note) to indicate a deprecation of the old meaning of the arguments?



On 11/7/18 11:09 AM, Daniel Henrique Barboza wrote:
changes in v3:
- rebased to v3.1.0-rc0 tag
- hmp-commands.hx documentation now mentions the change of semantics
starting version 3.2.
- previous version link:

It is not uncommon to see bugs being opened by testers that attempt to
create VM snapshots using HMP. It turns out that "0" and "1" are quite
common snapshot names and they trigger a lot of bugs. I gave an example
in the commit message of patch 1, but to sum up here: QEMU treats the
input of savevm/loadvm/delvm sometimes as 'ID', sometimes as 'name'. It
is documented as such, but this can lead to strange situations.

Given that it is strange for an API to consider a parameter to be 2 fields
at the same time, and inadvently treating them as one or the other, and
that removing the ID field is too drastic, my idea here is to keep the
ID field for internal control, but do not let the user set it.

This series simplifies the meaning of savevm/loadvm/delvm to be up to
par to what the QEMU code (and Libvirt) is already doing: snapshot
operations using "tag" semantics only, leaving the "id" to be
automatically calculated by the block drivers and used internally

This change of semantics does not affect existing snapshots. What
changes is that any HMP operations with them will use the
updated semantics.

Daniel Henrique Barboza (3):
   block/snapshot.c: eliminate use of ID input in snapshot operations
   block/snapshot: remove bdrv_snapshot_delete_by_id_or_name
   qcow2-snapshot: remove redundant find_snapshot_by_id_and_name call

  block/qcow2-snapshot.c   |  5 -----
  block/snapshot.c         | 25 +++----------------------
  hmp-commands.hx          | 32 ++++++++++++++++++++------------
  include/block/snapshot.h |  3 ---
  qemu-img.c               | 15 +++++++++++----
  5 files changed, 34 insertions(+), 46 deletions(-)

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