[Qemu-devel] [PATCH 4/5] block/backup: Add subclassed notifier

[John Snow <jsnow@redhat.com>]

Instead of relying on peeking at bs->job, we want to explicitly get
a reference to the job that was involved in this notifier callback.

Extend the Notifier to include a job pointer, and include a reference
to the job registering the callback. This cuts out a few more cases
where we have to rely on bs->job.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 block/backup.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/block/backup.c b/block/backup.c
index 325e247..58c76be 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -89,11 +89,11 @@ static void cow_request_end(CowRequest *req)
 }
 
 static int coroutine_fn backup_do_cow(BlockDriverState *bs,
+                                      BackupBlockJob *job,
                                       int64_t sector_num, int nb_sectors,
                                       bool *error_is_read,
                                       bool is_write_notifier)
 {
-    BackupBlockJob *job = (BackupBlockJob *)bs->job;
     CowRequest cow_request;
     struct iovec iov;
     QEMUIOVector bounce_qiov;
@@ -187,10 +187,17 @@ out:
     return ret;
 }
 
+/* Extend the generic Notifier interface */
+typedef struct BackupNotifier {
+    NotifierWithReturn common;
+    BackupBlockJob *job;
+} BackupNotifier;
+
 static int coroutine_fn backup_before_write_notify(
         NotifierWithReturn *notifier,
         void *opaque)
 {
+    BackupNotifier *bnotifier = (BackupNotifier *)notifier;
     BdrvTrackedRequest *req = opaque;
     int64_t sector_num = req->offset >> BDRV_SECTOR_BITS;
     int nb_sectors = req->bytes >> BDRV_SECTOR_BITS;
@@ -198,7 +205,8 @@ static int coroutine_fn backup_before_write_notify(
     assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0);
     assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 
-    return backup_do_cow(req->bs, sector_num, nb_sectors, NULL, true);
+    return backup_do_cow(req->bs, bnotifier->job, sector_num,
+                         nb_sectors, NULL, true);
 }
 
 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
@@ -346,7 +354,8 @@ static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
                 if (yield_and_check(job)) {
                     return ret;
                 }
-                ret = backup_do_cow(bs, cluster * BACKUP_SECTORS_PER_CLUSTER,
+                ret = backup_do_cow(bs, job,
+                                    cluster * BACKUP_SECTORS_PER_CLUSTER,
                                     BACKUP_SECTORS_PER_CLUSTER, &error_is_read,
                                     false);
                 if ((ret < 0) &&
@@ -382,8 +391,11 @@ static void coroutine_fn backup_run(void *opaque)
     BlockDriverState *bs = job->common.bs;
     BlockDriverState *target = job->target;
     BlockdevOnError on_target_error = job->on_target_error;
-    NotifierWithReturn before_write = {
-        .notify = backup_before_write_notify,
+    BackupNotifier before_write = {
+        .common = {
+            .notify = backup_before_write_notify,
+        },
+        .job = job,
     };
     int64_t start, end;
     int ret = 0;
@@ -402,7 +414,8 @@ static void coroutine_fn backup_run(void *opaque)
         blk_iostatus_enable(target->blk);
     }
 
-    bdrv_add_before_write_notifier(bs, &before_write);
+    block_job_ref(&job->common);
+    bdrv_add_before_write_notifier(bs, (NotifierWithReturn *)&before_write);
 
     if (job->sync_mode == MIRROR_SYNC_MODE_NONE) {
         while (!block_job_is_cancelled(&job->common)) {
@@ -454,7 +467,7 @@ static void coroutine_fn backup_run(void *opaque)
                 }
             }
             /* FULL sync mode we copy the whole drive. */
-            ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER,
+            ret = backup_do_cow(bs, job, start * BACKUP_SECTORS_PER_CLUSTER,
                     BACKUP_SECTORS_PER_CLUSTER, &error_is_read, false);
             if (ret < 0) {
                 /* Depending on error action, fail now or retry cluster */
@@ -470,7 +483,8 @@ static void coroutine_fn backup_run(void *opaque)
         }
     }
 
-    notifier_with_return_remove(&before_write);
+    notifier_with_return_remove((NotifierWithReturn *)&before_write);
+    block_job_unref(&job->common);
 
     /* wait until pending backup_do_cow() calls have completed */
     qemu_co_rwlock_wrlock(&job->flush_rwlock);
-- 
2.4.3