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Re: [Qemu-block] [PATCH 00/11] block: Deal with filters
Re: [Qemu-block] [PATCH 00/11] block: Deal with filters
Fri, 10 Aug 2018 00:26:58 +0200
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1
Let's pretend you didn't see this, as it breaks some iotests... *cough*
(This is what I get for last-minute changes and rebases without proper
test running. Yes, I'm ashamed.)
On 2018-08-09 23:37, Max Reitz wrote:
> Note 1: This series depends on v10 of my “block: Fix some filename
> generation issues” series.
> Based-on: <address@hidden>
> Note 2: This is technically the first part of my active mirror followup.
> But just very technically. I noticed that that followup started to
> consist of two parts, namely (A) fix filtery things in the block layer,
> and (B) fix active mirror. So I decided to split it. This is part A.
> Part B comes later.
> When we introduced filters, we did it a bit casually. Sure, we talked a
> lot about them before, but that was mostly discussion about where
> implicit filters should be added to the graph (note that we currently
> only have two implicit filters, those being mirror and commit). But in
> the end, we really just designated some drivers filters (Quorum,
> blkdebug, etc.) and added some specifically (throttle, COR), without
> really looking through the block layer to see where issues might occur.
> It turns out vast areas of the block layer just don't know about filters
> and cannot really handle them. Many cases will work in practice, in
> others, well, too bad, you cannot use some feature because some part
> deep inside the block layer looks at your filters and thinks they are
> format nodes.
> This series sets out to correct a bit of that. I lost my head many
> times and I'm sure this series is incomplete in many ways, but it really
> doesn't do any good if it sits on my disk any longer, it needs to go out
> The most important patches of this series are patches 3 and 4. These
> introduce functions to encapsulate bs->backing and bs->file accesses.
> Because sometimes, bs->backing means COW, sometimes it means filtered
> node. And sometimes, bs->file means metadata storage, and sometimes it
> means filtered node. With this functions, it's always clear what the
> caller wants, and it will always get what it wants.
> Besides that, patch 3 introduces functions to skip filters which may be
> used by parts of the block layer that just don't care about them.
> Secondly, the restraints put on mirror's @replaces parameter are
> revisited and fixed.
> Thirdly, BDS.backing_file is changed to be constant. I don't quite know
> why we modify it whenever we change a BDS's backing file, but that's
> definitely not quite right. This fixes things like being able to
> perform a commit on a file (using relative filenames) in a directory
> that's not qemu's CWD.
> Finally, a number of tests are added.
> There are probably many things that are worthy of discussion, of which
> only some come to my head, e.g.:
> - In which cases do we want to skip filters, in which cases do we want
> to skip implicit filters?
> My approach was to basically never skip explicitly added filters,
> except when it's about finding a file in some tree (e.g. in a backing
> chain). Maybe there are cases where you think we should skip even
> explicitly added filters.
> - I made interesting decisions like “When you mirror from a node, we
> should indeed mirror from that node, but when replacing it, we should
> skip leave all implicit filters on top intact.” You may disagree with
> (My reasoning here is that users aren't supposed to know about
> implicit filters, and therefore, they should not intend to remove
> them. Also, mirror accepts only root nodes as the source, so you
> cannot really specify the node below the implicit filters. But you
> can use @replaces to drop the implicit filters, if you know they are
> Max Reitz (11):
> block: Mark commit and mirror as filter drivers
> blockdev: Check @replaces in blockdev_mirror_common
> block: Filtered children access functions
> block: Storage child access function
> block: Fix check_to_replace_node()
> iotests: Add tests for mirror @replaces loops
> block: Leave BDS.backing_file constant
> iotests: Add filter commit test cases
> iotests: Add filter mirror test cases
> iotests: Add test for commit in sub directory
> iotests: Test committing to overridden backing
> qapi/block-core.json | 4 +
> include/block/block.h | 2 +
> include/block/block_int.h | 53 +++++-
> block.c | 338 ++++++++++++++++++++++++++++-----
> block/backup.c | 8 +-
> block/block-backend.c | 16 +-
> block/commit.c | 38 ++--
> block/io.c | 47 +++--
> block/mirror.c | 39 ++--
> block/qapi.c | 38 ++--
> block/snapshot.c | 40 ++--
> block/stream.c | 15 +-
> blockdev.c | 167 ++++++++++++----
> migration/block-dirty-bitmap.c | 4 +-
> nbd/server.c | 8 +-
> qemu-img.c | 24 ++-
> tests/qemu-iotests/020 | 36 ++++
> tests/qemu-iotests/020.out | 10 +
> tests/qemu-iotests/040 | 191 +++++++++++++++++++
> tests/qemu-iotests/040.out | 4 +-
> tests/qemu-iotests/041 | 270 +++++++++++++++++++++++++-
> tests/qemu-iotests/041.out | 4 +-
> tests/qemu-iotests/191.out | 1 -
> 23 files changed, 1133 insertions(+), 224 deletions(-)
Description: OpenPGP digital signature
- [Qemu-block] [PATCH 01/11] block: Mark commit and mirror as filter drivers, (continued)
- [Qemu-block] [PATCH 01/11] block: Mark commit and mirror as filter drivers, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 04/11] block: Storage child access function, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 03/11] block: Filtered children access functions, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 05/11] block: Fix check_to_replace_node(), Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 07/11] block: Leave BDS.backing_file constant, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 06/11] iotests: Add tests for mirror @replaces loops, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 09/11] iotests: Add filter mirror test cases, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 08/11] iotests: Add filter commit test cases, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 10/11] iotests: Add test for commit in sub directory, Max Reitz, 2018/08/09
- [Qemu-block] [PATCH 11/11] iotests: Test committing to overridden backing, Max Reitz, 2018/08/09
- Re: [Qemu-block] [PATCH 00/11] block: Deal with filters,
Max Reitz <=