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Re: [Qemu-block] [Qemu-devel] [PATCH v10 00/14] block: incremental backu
Re: [Qemu-block] [Qemu-devel] [PATCH v10 00/14] block: incremental backup transactions using BlockJobTxn
Mon, 2 Nov 2015 16:06:08 -0500
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To clarify, I *do* intend this series to be for-2.5, and I think it does
qualify as such.
If this *doesn't* go in, we have to revise our documentation just a
pinch to undo some of Kashyap's changes that have already been merged in.
Patches 5, 10, 11 and 12 are awaiting review.
On 10/23/2015 07:56 PM, John Snow wrote:
> Welcome to V10!
> Where'd 8 and 9 go? Private off-list missives from Fam.
> Now you, I, and everyone on qemu-devel are staring at V10.
> What's new in V10?
> I replaced the per-action "transactional-cancel" parameter with
> a per-transaction paremeter named "err-cancel" which is implemented
> as an enum in case we want to add new behaviors in the future, such
> as a "jobs only" cancel mode.
> For now, it's "all" or "none", and if you use it with actions that
> do not support the latent transactional cancel, you will receive
> an error for your troubles.
> This version primarily changed patches 10,11 and replaced it with
> patches 10-12 that are cut a little differently.
> This is based on top of the work by Stefan Hajnoczi and Fam Zheng.
> Recap: motivation for block job transactions
> If an incremental backup block job fails then we reclaim the bitmap so
> the job can be retried. The problem comes when multiple jobs are started as
> part of a qmp 'transaction' command. We need to group these jobs in a
> transaction so that either all jobs complete successfully or all bitmaps are
> Without transactions, there is a case where some jobs complete successfully
> throw away their bitmaps, making it impossible to retry the backup by
> the command if one of the jobs fails.
> How does this implementation work?
> These patches add a BlockJobTxn object with the following API:
> txn = block_job_txn_new();
> block_job_txn_add_job(txn, job1);
> block_job_txn_add_job(txn, job2);
> The jobs either both complete successfully or they both fail/cancel. If the
> user cancels job1 then job2 will also be cancelled and vice versa.
> Jobs objects stay alive waiting for other jobs to complete, even if the
> coroutines have returned. They can be cancelled by the user during this time.
> Job blockers are still in effect and no other block job can run on this device
> in the meantime (since QEMU currently only allows 1 job per device). This is
> the main drawback to this approach but reasonable since you probably don't
> to run other jobs/operations until you're sure the backup was successful (you
> won't be able to retry a failed backup if there's a new job running).
> v10: Replaced per-action parameter with per-transaction properties.
> Patches 10,11 were split into 10-12.
> v9: this version fixes a reference count problem with job->bs,
> in patch 05.
> v8: Rebase on to master.
> Minor fixes addressing John Snow's comments.
> v7: Add Eric's rev-by in 1, 11.
> Add Max's rev-by in 4, 5, 9, 10, 11.
> Add John's rev-by in 5, 6, 8.
> Fix wording for 6. [John]
> Fix comment of block_job_txn_add_job() in 9. [Max]
> Remove superfluous hunks, and document default value in 11. [Eric]
> Update Makefile dep in 14. [Max]
> For convenience, this branch is available at:
> https://github.com/jnsnow/qemu.git branch block-transpop
> This version is tagged block-transpop-v10:
> Fam Zheng (6):
> backup: Extract dirty bitmap handling as a separate function
> blockjob: Introduce reference count and fix reference to job->bs
> blockjob: Add .commit and .abort block job actions
> blockjob: Add "completed" and "ret" in BlockJob
> blockjob: Simplify block_job_finish_sync
> block: Add block job transactions
> John Snow (7):
> qapi: Add transaction support to block-dirty-bitmap operations
> iotests: add transactional incremental backup test
> block: rename BlkTransactionState and BdrvActionOps
> block/backup: Rely on commit/abort for cleanup
> block: Add BlockJobTxn support to backup_run
> block: add transactional properties
> iotests: 124 - transactional failure test
> Stefan Hajnoczi (1):
> tests: add BlockJobTxn unit test
> block.c | 19 +-
> block/backup.c | 50 ++++--
> block/mirror.c | 2 +-
> blockdev.c | 430
> blockjob.c | 188 ++++++++++++++++----
> docs/bitmaps.md | 6 +-
> include/block/block.h | 2 +-
> include/block/block_int.h | 6 +-
> include/block/blockjob.h | 85 ++++++++-
> qapi-schema.json | 54 +++++-
> qemu-img.c | 3 -
> qmp-commands.hx | 2 +-
> tests/Makefile | 3 +
> tests/qemu-iotests/124 | 182 ++++++++++++++++++-
> tests/qemu-iotests/124.out | 4 +-
> tests/test-blockjob-txn.c | 244 +++++++++++++++++++++++++
> 16 files changed, 1108 insertions(+), 172 deletions(-)
> create mode 100644 tests/test-blockjob-txn.c
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John Snow <=