[Qemu-devel] [PATCH] job: drop job_drain

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

In job_finish_sync job_enter should be enough for a job to make some
progress and draining is a wrong tool for it. So use job_enter directly
here and drop job_drain with all related staff not used more.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---

It's a continuation for
   [PATCH v4] blockjob: drain all job nodes in block_job_drain

 include/block/blockjob_int.h | 19 -------------------
 include/qemu/job.h           | 13 -------------
 block/backup.c               | 19 +------------------
 block/commit.c               |  1 -
 block/mirror.c               | 28 +++-------------------------
 block/stream.c               |  1 -
 blockjob.c                   | 13 -------------
 job.c                        | 12 +-----------
 8 files changed, 5 insertions(+), 101 deletions(-)

diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h
index e4a318dd15..e2824a36a8 100644
--- a/include/block/blockjob_int.h
+++ b/include/block/blockjob_int.h
@@ -52,17 +52,6 @@ struct BlockJobDriver {
      * besides job->blk to the new AioContext.
      */
     void (*attached_aio_context)(BlockJob *job, AioContext *new_context);
-
-    /*
-     * If the callback is not NULL, it will be invoked when the job has to be
-     * synchronously cancelled or completed; it should drain BlockDriverStates
-     * as required to ensure progress.
-     *
-     * Block jobs must use the default implementation for job_driver.drain,
-     * which will in turn call this callback after doing generic block job
-     * stuff.
-     */
-    void (*drain)(BlockJob *job);
 };
 
 /**
@@ -107,14 +96,6 @@ void block_job_free(Job *job);
  */
 void block_job_user_resume(Job *job);
 
-/**
- * block_job_drain:
- * Callback to be used for JobDriver.drain in all block jobs. Drains the main
- * block node associated with the block jobs and calls BlockJobDriver.drain for
- * job-specific actions.
- */
-void block_job_drain(Job *job);
-
 /**
  * block_job_ratelimit_get_delay:
  *
diff --git a/include/qemu/job.h b/include/qemu/job.h
index 9e7cd1e4a0..09739b8dd9 100644
--- a/include/qemu/job.h
+++ b/include/qemu/job.h
@@ -220,13 +220,6 @@ struct JobDriver {
      */
     void (*complete)(Job *job, Error **errp);
 
-    /*
-     * If the callback is not NULL, it will be invoked when the job has to be
-     * synchronously cancelled or completed; it should drain any activities
-     * as required to ensure progress.
-     */
-    void (*drain)(Job *job);
-
     /**
      * 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
@@ -470,12 +463,6 @@ bool job_user_paused(Job *job);
  */
 void job_user_resume(Job *job, Error **errp);
 
-/*
- * Drain any activities as required to ensure progress. This can be called in a
- * loop to synchronously complete a job.
- */
-void job_drain(Job *job);
-
 /**
  * Get the next element from the list of block jobs after @job, or the
  * first one if @job is %NULL.
diff --git a/block/backup.c b/block/backup.c
index 715e1d3be8..d1ecdfa9aa 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -320,21 +320,6 @@ void backup_do_checkpoint(BlockJob *job, Error **errp)
     hbitmap_set(backup_job->copy_bitmap, 0, backup_job->len);
 }
 
-static void backup_drain(BlockJob *job)
-{
-    BackupBlockJob *s = container_of(job, BackupBlockJob, common);
-
-    /* Need to keep a reference in case blk_drain triggers execution
-     * of backup_complete...
-     */
-    if (s->target) {
-        BlockBackend *target = s->target;
-        blk_ref(target);
-        blk_drain(target);
-        blk_unref(target);
-    }
-}
-
 static BlockErrorAction backup_error_action(BackupBlockJob *job,
                                             bool read, int error)
 {
@@ -488,13 +473,11 @@ static const BlockJobDriver backup_job_driver = {
         .job_type               = JOB_TYPE_BACKUP,
         .free                   = block_job_free,
         .user_resume            = block_job_user_resume,
-        .drain                  = block_job_drain,
         .run                    = backup_run,
         .commit                 = backup_commit,
         .abort                  = backup_abort,
         .clean                  = backup_clean,
-    },
-    .drain                  = backup_drain,
+    }
 };
 
 static int64_t backup_calculate_cluster_size(BlockDriverState *target,
diff --git a/block/commit.c b/block/commit.c
index 2c5a6d4ebc..697a779d8e 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -216,7 +216,6 @@ static const BlockJobDriver commit_job_driver = {
         .job_type      = JOB_TYPE_COMMIT,
         .free          = block_job_free,
         .user_resume   = block_job_user_resume,
-        .drain         = block_job_drain,
         .run           = commit_run,
         .prepare       = commit_prepare,
         .abort         = commit_abort,
diff --git a/block/mirror.c b/block/mirror.c
index 8cb75fb409..b91abe0288 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -644,14 +644,11 @@ static int mirror_exit_common(Job *job)
     bdrv_ref(mirror_top_bs);
     bdrv_ref(target_bs);
 
-    /* Remove target parent that still uses BLK_PERM_WRITE/RESIZE before
+    /*
+     * Remove target parent that still uses BLK_PERM_WRITE/RESIZE before
      * inserting target_bs at s->to_replace, where we might not be able to get
      * these permissions.
-     *
-     * Note that blk_unref() alone doesn't necessarily drop permissions because
-     * we might be running nested inside mirror_drain(), which takes an extra
-     * reference, so use an explicit blk_set_perm() first. */
-    blk_set_perm(s->target, 0, BLK_PERM_ALL, &error_abort);
+     */
     blk_unref(s->target);
     s->target = NULL;
 
@@ -1143,28 +1140,12 @@ static bool mirror_drained_poll(BlockJob *job)
     return !!s->in_flight;
 }
 
-static void mirror_drain(BlockJob *job)
-{
-    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
-
-    /* Need to keep a reference in case blk_drain triggers execution
-     * of mirror_complete...
-     */
-    if (s->target) {
-        BlockBackend *target = s->target;
-        blk_ref(target);
-        blk_drain(target);
-        blk_unref(target);
-    }
-}
-
 static const BlockJobDriver mirror_job_driver = {
     .job_driver = {
         .instance_size          = sizeof(MirrorBlockJob),
         .job_type               = JOB_TYPE_MIRROR,
         .free                   = block_job_free,
         .user_resume            = block_job_user_resume,
-        .drain                  = block_job_drain,
         .run                    = mirror_run,
         .prepare                = mirror_prepare,
         .abort                  = mirror_abort,
@@ -1172,7 +1153,6 @@ static const BlockJobDriver mirror_job_driver = {
         .complete               = mirror_complete,
     },
     .drained_poll           = mirror_drained_poll,
-    .drain                  = mirror_drain,
 };
 
 static const BlockJobDriver commit_active_job_driver = {
@@ -1181,7 +1161,6 @@ static const BlockJobDriver commit_active_job_driver = {
         .job_type               = JOB_TYPE_COMMIT,
         .free                   = block_job_free,
         .user_resume            = block_job_user_resume,
-        .drain                  = block_job_drain,
         .run                    = mirror_run,
         .prepare                = mirror_prepare,
         .abort                  = mirror_abort,
@@ -1189,7 +1168,6 @@ static const BlockJobDriver commit_active_job_driver = {
         .complete               = mirror_complete,
     },
     .drained_poll           = mirror_drained_poll,
-    .drain                  = mirror_drain,
 };
 
 static void coroutine_fn
diff --git a/block/stream.c b/block/stream.c
index 6ac1e7bec4..07f9908e1a 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -218,7 +218,6 @@ static const BlockJobDriver stream_job_driver = {
         .abort         = stream_abort,
         .clean         = stream_clean,
         .user_resume   = block_job_user_resume,
-        .drain         = block_job_drain,
     },
 };
 
diff --git a/blockjob.c b/blockjob.c
index 20b7f557da..4b8d0869c6 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -89,18 +89,6 @@ void block_job_free(Job *job)
     error_free(bjob->blocker);
 }
 
-void block_job_drain(Job *job)
-{
-    BlockJob *bjob = container_of(job, BlockJob, job);
-    const JobDriver *drv = job->driver;
-    BlockJobDriver *bjdrv = container_of(drv, BlockJobDriver, job_driver);
-
-    blk_drain(bjob->blk);
-    if (bjdrv->drain) {
-        bjdrv->drain(bjob);
-    }
-}
-
 static char *child_job_get_parent_desc(BdrvChild *c)
 {
     BlockJob *job = c->opaque;
@@ -421,7 +409,6 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     assert(is_block_job(&job->job));
     assert(job->job.driver->free == &block_job_free);
     assert(job->job.driver->user_resume == &block_job_user_resume);
-    assert(job->job.driver->drain == &block_job_drain);
 
     job->blk = blk;
 
diff --git a/job.c b/job.c
index 28dd48f8a5..04409b40aa 100644
--- a/job.c
+++ b/job.c
@@ -523,16 +523,6 @@ void coroutine_fn job_sleep_ns(Job *job, int64_t ns)
     job_pause_point(job);
 }
 
-void job_drain(Job *job)
-{
-    /* If job is !busy this kicks it into the next pause point. */
-    job_enter(job);
-
-    if (job->driver->drain) {
-        job->driver->drain(job);
-    }
-}
-
 /* Assumes the block_job_mutex is held */
 static bool job_timer_not_pending(Job *job)
 {
@@ -991,7 +981,7 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), Error **errp)
     }
 
     AIO_WAIT_WHILE(job->aio_context,
-                   (job_drain(job), !job_is_completed(job)));
+                   (job_enter(job), !job_is_completed(job)));
 
     ret = (job_is_cancelled(job) && job->ret == 0) ? -ECANCELED : job->ret;
     job_unref(job);
-- 
2.18.0