On Thu, Jun 25, 2015 at 01:12:02PM +0100, Stefan Hajnoczi wrote: > This series is based on my block branch > (https://github.com/stefanha/qemu/commits/block). > > It uses patches from John Snow's "[PATCH v6 00/10] block: incremental backup > transactions" series but implements the feature with a new transaction > mechanism for blockjobs called BlockJobTxn. > > 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 > reclaimed. > > Without transactions, there is a case where some jobs complete successfully > and > throw away their bitmaps, making it impossible to retry the backup by > rerunning > 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); > block_job_txn_begin(); > > 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 stay alive waiting for other jobs to complete. 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 want 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). > > Adding transaction support to the backup job is very easy. It just needs to > make a call before throwing away the bitmap and returning from its coroutine: > > block_job_txn_prepare_to_complete(job->txn, job, ret); > > if (job->sync_bitmap) { > BdrvDirtyBitmap *bm; > if (ret < 0 || block_job_is_cancelled(&job->common)) { > ... > > John Snow (4): > qapi: Add transaction support to block-dirty-bitmap operations > iotests: add transactional incremental backup test > block: rename BlkTransactionState and BdrvActionOps > iotests: 124 - transactional failure test > > Kashyap Chamarthy (1): > qmp-commands.hx: Update the supported 'transaction' operations > > Stefan Hajnoczi (5): > block: keep bitmap if incremental backup job is cancelled > block: add block job transactions > blockdev: make BlockJobTxn available to qmp 'transaction' > block/backup: support block job transactions > tests: add BlockJobTxn unit test > > block.c | 19 ++- > block/backup.c | 9 +- > blockdev.c | 298 > +++++++++++++++++++++++++++++++++++---------- > blockjob.c | 160 ++++++++++++++++++++++++ > docs/bitmaps.md | 6 +- > include/block/block.h | 2 +- > include/block/block_int.h | 6 +- > include/block/blockjob.h | 49 ++++++++ > qapi-schema.json | 6 +- > qmp-commands.hx | 21 +++- > tests/Makefile | 3 + > tests/qemu-iotests/124 | 180 ++++++++++++++++++++++++++- > tests/qemu-iotests/124.out | 4 +- > tests/test-blockjob-txn.c | 191 +++++++++++++++++++++++++++++ > trace-events | 4 + > 15 files changed, 873 insertions(+), 85 deletions(-) > create mode 100644 tests/test-blockjob-txn.c
John: Do you want to review this series?
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