From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51768) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEqWX-0003LV-84 for qemu-devel@nongnu.org; Mon, 13 Jul 2015 23:04:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZEqWS-0006OD-3a for qemu-devel@nongnu.org; Mon, 13 Jul 2015 23:04:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55698) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEqWR-0006NX-R9 for qemu-devel@nongnu.org; Mon, 13 Jul 2015 23:04:44 -0400 Date: Tue, 14 Jul 2015 11:04:39 +0800 From: Fam Zheng Message-ID: <20150714030439.GA24907@ad.nay.redhat.com> References: <1436500012-32593-1-git-send-email-famz@redhat.com> <1436500012-32593-11-git-send-email-famz@redhat.com> <55A445CA.4040306@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55A445CA.4040306@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3 10/15] block: add block job transactions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow Cc: Kevin Wolf , Jeff Cody , qemu-devel@nongnu.org, Max Reitz , vsementsov@parallels.com, stefanha@redhat.com On Mon, 07/13 19:12, John Snow wrote: > > > On 07/09/2015 11:46 PM, Fam Zheng wrote: > > From: Stefan Hajnoczi > > > > Sometimes block jobs must execute as a transaction group. Finishing > > jobs wait until all other jobs are ready to complete successfully. > > Failure or cancellation of one job cancels the other jobs in the group. > > > > Signed-off-by: Stefan Hajnoczi > > [Rewrite the implementation which is now contained in block_job_completed. > > --Fam] > > Signed-off-by: Fam Zheng > > --- > > blockjob.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++ > > include/block/block.h | 1 + > > include/block/blockjob.h | 26 +++++++++++++++ > > 3 files changed, 113 insertions(+) > > > > diff --git a/blockjob.c b/blockjob.c > > index e057dd5..7b59b53 100644 > > --- a/blockjob.c > > +++ b/blockjob.c > > @@ -36,6 +36,16 @@ > > #include "qemu/timer.h" > > #include "qapi-event.h" > > > > +/* Transactional group of block jobs */ > > +struct BlockJobTxn { > > + > > + /* Is this txn being cancelled? */ > > + bool aborting; > > + > > + /* List of jobs */ > > + QLIST_HEAD(, BlockJob) jobs; > > +}; > > + > > void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs, > > int64_t speed, BlockCompletionFunc *cb, > > void *opaque, Error **errp) > > @@ -84,6 +94,59 @@ void block_job_release(BlockDriverState *bs) > > g_free(job); > > } > > > > +static void block_job_completed_txn(BlockJobTxn *txn, BlockJob *job, int ret) > > +{ > > + AioContext *ctx; > > + BlockJob *other_job, *next; > > + if (ret < 0 || block_job_is_cancelled(job)) { > > + if (!txn->aborting) { > > + /* We are the first failed job. Cancel other jobs. */ > > What guarantee against a race is there at this point? Something to do > with deferring back to the main loop before we call completion? This is always in the main thread, so there can't be any race. > > Do jobs always complete in the main thread? Yes. > > > + txn->aborting = true; > > + QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) { > > + if (other_job == job || other_job->completed) { > > + continue; > > + } > > + ctx = bdrv_get_aio_context(other_job->bs); > > + aio_context_acquire(ctx); > > + block_job_cancel_sync(other_job); > > + assert(other_job->completed); > > + aio_context_release(ctx); > > + } > > + QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) { > > + if (other_job->driver->txn_abort) { > > + other_job->driver->txn_abort(other_job); > > + } > > + other_job->cb(other_job->opaque, > > + other_job->ret ? : -ECANCELED); > > + block_job_release(other_job->bs); > > + } > > + } else { > > + /* > > + * We are cancelled by another job, who will handle everything. > > + */ > > + return; > > + } > > + } else { > > + /* > > + * Successful completion, see if there is other running jobs in this > > + * txn. */ > > s/is/are/ OK. > > > + QLIST_FOREACH(other_job, &txn->jobs, txn_list) { > > + if (!other_job->completed) { > > + return; > > + } > > + } > > Clever (though quadratic!) :~) If someone suggest there could be 1000+ jobs in a txn, I can add a counter. > > > + /* We are the last completed job, commit the transaction. */ > > + QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) { > > + if (other_job->driver->txn_commit) { > > + other_job->driver->txn_commit(other_job); > > + } > > + assert(other_job->ret == 0); > > + other_job->cb(other_job->opaque, 0); > > + block_job_release(other_job->bs); > > Worth creating some static local/inline routine and sharing it with > block_job_completed? Mayb when a 3rd common line comes? > > > + } > > + } > > +} > > + > > void block_job_completed(BlockJob *job, int ret) > > { > > BlockDriverState *bs = job->bs; > > @@ -96,6 +159,10 @@ void block_job_completed(BlockJob *job, int ret) > > qemu_bh_delete(job->defer_to_main_loop_data.bh); > > job->defer_to_main_loop_data.bh = NULL; > > } > > + if (job->txn) { > > + block_job_completed_txn(job->txn, job, ret); > > + return; > > + } > > job->cb(job->opaque, ret); > > block_job_release(bs); > > } > > @@ -384,3 +451,22 @@ void block_job_defer_to_main_loop(BlockJob *job, > > > > qemu_bh_schedule(data->bh); > > } > > + > > +BlockJobTxn *block_job_txn_new(void) > > +{ > > + BlockJobTxn *txn = g_new0(BlockJobTxn, 1); > > + QLIST_INIT(&txn->jobs); > > + return txn; > > +} > > + > > +void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job) > > +{ > > + if (!txn) { > > + return; > > + } > > + > > + assert(!job->txn); > > + job->txn = txn; > > + > > + QLIST_INSERT_HEAD(&txn->jobs, job, txn_list); > > +} > > diff --git a/include/block/block.h b/include/block/block.h > > index 7437590..c7fc5b6 100644 > > --- a/include/block/block.h > > +++ b/include/block/block.h > > @@ -13,6 +13,7 @@ > > typedef struct BlockDriver BlockDriver; > > typedef struct BlockJob BlockJob; > > typedef struct BdrvChildRole BdrvChildRole; > > +typedef struct BlockJobTxn BlockJobTxn; > > > > typedef struct BlockDriverInfo { > > /* in bytes, 0 if irrelevant */ > > diff --git a/include/block/blockjob.h b/include/block/blockjob.h > > index 5bac2e2..d854ee0 100644 > > --- a/include/block/blockjob.h > > +++ b/include/block/blockjob.h > > @@ -157,6 +157,9 @@ struct BlockJob { > > */ > > int ret; > > > > + /** Non-NULL if this job is part of a transaction */ > > + BlockJobTxn *txn; > > + QLIST_ENTRY(BlockJob) txn_list; > > }; > > > > /** > > @@ -389,4 +392,27 @@ void block_job_defer_to_main_loop(BlockJob *job, > > BlockJobDeferToMainLoopFn *fn, > > void *opaque); > > > > +/** > > + * block_job_txn_new: > > + * > > + * Allocate and return a new block job transaction. Jobs can be added to the > > + * transaction using block_job_txn_add_job(). > > + * > > + * All jobs in the transaction either complete successfully or fail/cancel as a > > + * group. Jobs wait for each other before completing. Cancelling one job > > + * cancels all jobs in the transaction. > > + */ > > +BlockJobTxn *block_job_txn_new(void); > > + > > +/** > > + * block_job_txn_add_job: > > + * @txn: The transaction (may be NULL) > > + * @job: Job to add to the transaction > > + * > > + * Add @job to the transaction. The @job must not already be in a transaction. > > + * The block job driver must call block_job_txn_prepare_to_complete() before > > + * final cleanup and completion. > > + */ > > +void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job); > > + > > #endif > > > > This definitely combines the best of our approaches AND has less code to > boot. Great! > > Nitpicks and comment spelling aside: > Reviewed-by: John Snow Thanks! > > -- > (linguistic postscript: I don't know how to say "Stefan and I's patches" > because I think 'I' is incorrect here because the subject of the > sentence is the patches, not Stefan or myself. I think it's some variant > on "me" "my" or "mine," but can't quite work it out. English is hard, or > I'm stupid, or both.) > LOL! Fam