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List: qemu-block
Subject: Re: [Qemu-block] [PATCH v19 00/10] Block replication for continuous checkpoints
From: Changlong Xie <xiecl.fnst () cn ! fujitsu ! com>
Date: 2016-05-31 10:25:16
Message-ID: 574D668C.4050102 () cn ! fujitsu ! com
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On 05/31/2016 02:20 AM, Stefan Hajnoczi wrote:
> On Fri, May 20, 2016 at 03:36:10PM +0800, Changlong Xie wrote:
>> Block replication is a very important feature which is used for
>> continuous checkpoints(for example: COLO).
>>
>> You can get the detailed information about block replication from here:
>> http://wiki.qemu.org/Features/BlockReplication
>>
>> Usage:
>> Please refer to docs/block-replication.txt
>>
>> You can get the patch here:
>> https://github.com/Pating/qemu/tree/changlox/block-replication-v19
>>
>> You can get the patch with framework here:
>> https://github.com/Pating/qemu/tree/changlox/colo_framework_v18
>>
>> TODO:
>> 1. Continuous block replication. It will be started after basic functions
>> are accepted.
>>
>> Changs Log:
>> V19:
>> 1. Rebase to v2.6.0
>> 2. Address comments from stefan
>> p3: a new patch that export interfaces for extra serialization
>> p8:
>> 1. call replication_stop() before freeing s->top_id
>> 2. check top_bs
>> 3. reopen file readonly in error return paths
>> 4. enable extra serialization between read and COW
>> p9: try to hanlde SIGABRT
>> V18:
>> p6: add local_err in all replication callbacks to prevent "errp == NULL"
>> p7: add missing qemu_iovec_destroy(xxx)
>> V17:
>> 1. Rebase to the lastest codes
>> p2: refactor backup_do_checkpoint addressed comments from Jeff Cody
>> p4: fix bugs in "drive_add buddy xxx" hmp commands
>> p6: add "since: 2.7"
>> p7: fix bug in replication_close(), add missing "qapi/error.h", add test-replication
>> p8: add "since: 2.7"
>> V16:
>> 1. Rebase to the newest codes
>> 2. Address comments from Stefan & hailiang
>> p3: we don't need this patch now
>> p4: add "top-id" parameters for secondary
>> p6: fix NULL pointer in replication callbacks, remove unnecessary typedefs,
>> add doc comments that explain the semantics of Replication
>> p7: Refactor AioContext for thread-safe, remove unnecessary get_top_bs()
>> *Note*: I'm working on replication testcase now, will send out in V17
>> V15:
>> 1. Rebase to the newest codes
>> 2. Fix typos and coding style addresed Eric's comments
>> 3. Address Stefan's comments
>> 1) Make backup_do_checkpoint public, drop the changes on BlockJobDriver
>> 2) Update the message and description for [PATCH 4/9]
>> 3) Make replication_(start/stop/do_checkpoint)_all as global interfaces
>> 4) Introduce AioContext lock to protect start/stop/do_checkpoint callbacks
>> 5) Use BdrvChild instead of holding on to BlockDriverState * pointers
>> 4. Clear BDRV_O_INACTIVE for hidden disk's open_flags since commit 09e0c771
>> 5. Introduce replication_get_error_all to check replication status
>> 6. Remove useless discard interface
>> V14:
>> 1. Implement auto complete active commit
>> 2. Implement active commit block job for replication.c
>> 3. Address the comments from Stefan, add replication-specific API and data
>> structure, also remove old block layer APIs
>> V13:
>> 1. Rebase to the newest codes
>> 2. Remove redundant marcos and semicolon in replication.c
>> 3. Fix typos in block-replication.txt
>> V12:
>> 1. Rebase to the newest codes
>> 2. Use backing reference to replcace 'allow-write-backing-file'
>> V11:
>> 1. Reopen the backing file when starting blcok replication if it is not
>> opened in R/W mode
>> 2. Unblock BLOCK_OP_TYPE_BACKUP_SOURCE and BLOCK_OP_TYPE_BACKUP_TARGET
>> when opening backing file
>> 3. Block the top BDS so there is only one block job for the top BDS and
>> its backing chain.
>> V10:
>> 1. Use blockdev-remove-medium and blockdev-insert-medium to replace backing
>> reference.
>> 2. Address the comments from Eric Blake
>> V9:
>> 1. Update the error messages
>> 2. Rebase to the newest qemu
>> 3. Split child add/delete support. These patches are sent in another patchset.
>> V8:
>> 1. Address Alberto Garcia's comments
>> V7:
>> 1. Implement adding/removing quorum child. Remove the option non-connect.
>> 2. Simplify the backing refrence option according to Stefan Hajnoczi's suggestion
>> V6:
>> 1. Rebase to the newest qemu.
>> V5:
>> 1. Address the comments from Gong Lei
>> 2. Speed the failover up. The secondary vm can take over very quickly even
>> if there are too many I/O requests.
>> V4:
>> 1. Introduce a new driver replication to avoid touch nbd and qcow2.
>> V3:
>> 1: use error_setg() instead of error_set()
>> 2. Add a new block job API
>> 3. Active disk, hidden disk and nbd target uses the same AioContext
>> 4. Add a testcase to test new hbitmap API
>> V2:
>> 1. Redesign the secondary qemu(use image-fleecing)
>> 2. Use Error objects to return error message
>> 3. Address the comments from Max Reitz and Eric Blake
>>
>> Changlong Xie (3):
>> Backup: export interfaces for extra serialization
>> Introduce new APIs to do replication operation
>> tests: add unit test case for replication
>>
>> Wen Congyang (7):
>> unblock backup operations in backing file
>> Backup: clear all bitmap when doing block checkpoint
>> Link backup into block core
>> docs: block replication's description
>> auto complete active commit
>> Implement new driver for block replication
>> support replication driver in blockdev-add
>>
>> Makefile.objs | 1 +
>> block.c | 17 ++
>> block/Makefile.objs | 3 +-
>> block/backup.c | 59 +++-
>> block/mirror.c | 13 +-
>> block/replication.c | 666 +++++++++++++++++++++++++++++++++++++++++++
>> blockdev.c | 2 +-
>> docs/block-replication.txt | 239 ++++++++++++++++
>> include/block/block_backup.h | 17 ++
>> include/block/block_int.h | 3 +-
>> qapi/block-core.json | 33 ++-
>> qemu-img.c | 2 +-
>> replication.c | 105 +++++++
>> replication.h | 176 ++++++++++++
>> tests/.gitignore | 1 +
>> tests/Makefile | 4 +
>> tests/test-replication.c | 523 +++++++++++++++++++++++++++++++++
>> 17 files changed, 1847 insertions(+), 17 deletions(-)
>> create mode 100644 block/replication.c
>> create mode 100644 docs/block-replication.txt
>> create mode 100644 include/block/block_backup.h
>> create mode 100644 replication.c
>> create mode 100644 replication.h
>> create mode 100644 tests/test-replication.c
>
> I have reviewed many revisions of this series. The main mechanism in
> this series makes sense to me.
>
Thanks.
> I'm still concerned that checkpointing (vm_stop(), not in this series
> but COLO in general) depends on bdrv_drain(), which can block forever if
> I/O is hung. That doesn't seem like a reasonable limitation for a high
> availability feature since it may lead to the VM becoming unavailable.
IIRC, this issue is mentioned in my older patchset.
>
> I'd like Jeff and/or Kevin to review this series and merge it once they
> are happy.
>
@jeff, kevin and all block maintainters, would you like to review this
patchset?
Thanks
-Xie
> Stefan
>
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