From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55441) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1epN8Q-0005xq-P2 for qemu-devel@nongnu.org; Fri, 23 Feb 2018 18:52:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1epN8N-000625-CT for qemu-devel@nongnu.org; Fri, 23 Feb 2018 18:52:14 -0500 From: John Snow Date: Fri, 23 Feb 2018 18:51:36 -0500 Message-Id: <20180223235142.21501-16-jsnow@redhat.com> In-Reply-To: <20180223235142.21501-1-jsnow@redhat.com> References: <20180223235142.21501-1-jsnow@redhat.com> Subject: [Qemu-devel] [RFC v4 15/21] blockjobs: add prepare callback List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, pkrempa@redhat.com, jtc@redhat.com, qemu-devel@nongnu.org, John Snow Some jobs upon finalization may need to perform some work that can still fail. If these jobs are part of a transaction, it's important that these callbacks fail the entire transaction. We allow for a new callback in addition to commit/abort/clean that allows us the opportunity to have fairly late-breaking failures in the transactional process. The expected flow is: - All jobs in a transaction converge to the WAITING state (added in a forthcoming commit) - All jobs prepare to call either commit/abort - If any job fails, is canceled, or fails preparation, all jobs call their .abort callback. - All jobs enter the PENDING state, awaiting manual intervention (also added in a forthcoming commit) - block-job-finalize is issued by the user/management layer - All jobs call their commit callbacks. Signed-off-by: John Snow --- blockjob.c | 34 +++++++++++++++++++++++++++++++--- include/block/blockjob_int.h | 10 ++++++++++ 2 files changed, 41 insertions(+), 3 deletions(-) diff --git a/blockjob.c b/blockjob.c index 8f02c03880..1c010ec100 100644 --- a/blockjob.c +++ b/blockjob.c @@ -394,6 +394,18 @@ static void block_job_update_rc(BlockJob *job) } } +static int block_job_prepare(BlockJob *job) +{ + if (job->ret) { + goto out; + } + if (job->driver->prepare) { + job->ret = job->driver->prepare(job); + } + out: + return job->ret; +} + static void block_job_commit(BlockJob *job) { assert(!job->ret); @@ -417,7 +429,7 @@ static void block_job_clean(BlockJob *job) } } -static void block_job_completed_single(BlockJob *job) +static int block_job_completed_single(BlockJob *job) { assert(job->completed); @@ -452,6 +464,7 @@ static void block_job_completed_single(BlockJob *job) block_job_txn_unref(job->txn); block_job_event_concluded(job); block_job_unref(job); + return 0; } static void block_job_cancel_async(BlockJob *job) @@ -467,17 +480,22 @@ static void block_job_cancel_async(BlockJob *job) job->cancelled = true; } -static void block_job_txn_apply(BlockJobTxn *txn, void fn(BlockJob *)) +static int block_job_txn_apply(BlockJobTxn *txn, int fn(BlockJob *)) { AioContext *ctx; BlockJob *job, *next; + int rc; QLIST_FOREACH_SAFE(job, &txn->jobs, txn_list, next) { ctx = blk_get_aio_context(job->blk); aio_context_acquire(ctx); - fn(job); + rc = fn(job); aio_context_release(ctx); + if (rc) { + break; + } } + return rc; } static void block_job_do_dismiss(BlockJob *job) @@ -567,6 +585,8 @@ static void block_job_completed_txn_success(BlockJob *job) { BlockJobTxn *txn = job->txn; BlockJob *other_job; + int rc = 0; + /* * Successful completion, see if there are other running jobs in this * txn. @@ -576,6 +596,14 @@ static void block_job_completed_txn_success(BlockJob *job) return; } } + + /* Jobs may require some prep-work to complete without failure */ + rc = block_job_txn_apply(txn, block_job_prepare); + if (rc) { + block_job_completed_txn_abort(job); + return; + } + /* We are the last completed job, commit the transaction. */ block_job_txn_apply(txn, block_job_completed_single); } diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h index 259d49b32a..642adce68b 100644 --- a/include/block/blockjob_int.h +++ b/include/block/blockjob_int.h @@ -53,6 +53,16 @@ struct BlockJobDriver { */ void (*complete)(BlockJob *job, Error **errp); + /** + * If the callback is not NULL, prepare will be invoked when all the jobs + * belonging to the same transaction complete; or upon this job's completion + * if it is not in a transaction. + * + * This callback will not be invoked if the job has already failed. + * If it fails, abort and then clean will be called. + */ + int (*prepare)(BlockJob *job); + /** * If the callback is not NULL, it will be invoked when all the jobs * belonging to the same transaction complete; or upon this job's -- 2.14.3