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[Qemu-block] [RFC v4 15/21] blockjobs: add prepare callback
From: |
John Snow |
Subject: |
[Qemu-block] [RFC v4 15/21] blockjobs: add prepare callback |
Date: |
Fri, 23 Feb 2018 18:51:36 -0500 |
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 <address@hidden>
---
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
- Re: [Qemu-block] [Qemu-devel] [RFC v4 08/21] blockjobs: add ABORTING state, (continued)