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Re: [PATCH v2 07/33] block: rename backup-top to copy-before-write


From: Max Reitz
Subject: Re: [PATCH v2 07/33] block: rename backup-top to copy-before-write
Date: Mon, 31 May 2021 18:08:40 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1

On 20.05.21 16:21, Vladimir Sementsov-Ogievskiy wrote:
We are going to convert backup_top to full featured public filter,
which can be used in separate of backup job. Start from renaming from
"how it used" to "what it does".

While updating comments in 283 iotest, drop and rephrase also things
about ".active", as this field is now dropped, and filter doesn't have
"inactive" mode.

Note that this change may be considered as incompatible interface
change, as backup-top filter format name was visible through
query-block and query-named-block-nodes.

Still, consider the following reasoning:

1. backup-top was never documented, so if someone depends on format
    name (for driver that can't be used other than it is automatically
    inserted on backup job start), it's a kind of "undocumented feature
    use". So I think we are free to change it.

2. There is a hope, that there is no such users: it's a lot more native
    to give a good node-name to backup-top filter if need to operate
    with it somehow, and don't touch format name.

3. Another "incompatible" change in further commit would be moving
    copy-before-write filter from using backing child to file child. And
    this is even more reasonable than renaming: for now all public
    filters are file-child based.

So, it's a risky change, but risk seems small and good interface worth
it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
  block/{backup-top.h => copy-before-write.h} |  28 +++---
  block/backup.c                              |  22 ++---
  block/{backup-top.c => copy-before-write.c} | 100 ++++++++++----------
  MAINTAINERS                                 |   4 +-
  block/meson.build                           |   2 +-
  tests/qemu-iotests/283                      |  35 +++----
  tests/qemu-iotests/283.out                  |   4 +-
  7 files changed, 95 insertions(+), 100 deletions(-)
  rename block/{backup-top.h => copy-before-write.h} (56%)
  rename block/{backup-top.c => copy-before-write.c} (62%)

Reviewed-by: Max Reitz <mreitz@redhat.com>




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