block/block-copy: fix progress calculation

Assume we have two regions, A and B, and region B is in-flight now,
region A is not yet touched, but it is unallocated and should be
skipped.

Correspondingly, as progress we have

  total = A + B
  current = 0

If we reset unallocated region A and call progress_reset_callback,
it will calculate 0 bytes dirty in the bitmap and call
job_progress_set_remaining, which will set

   total = current + 0 = 0 + 0 = 0

So, B bytes are actually removed from total accounting. When job
finishes we'll have

   total = 0
   current = B

, which doesn't sound good.

This is because we didn't considered in-flight bytes, actually when
calculating remaining, we should have set (in_flight + dirty_bytes)
as remaining, not only dirty_bytes.

To fix it, let's refactor progress calculation, moving it to block-copy
itself instead of fixing callback. And, of course, track in_flight
bytes count.

We still have to keep one callback, to maintain backup job bytes_read
calculation, but it will go on soon, when we turn the whole backup
process into one block_copy call.

Cc: qemu-stable@nongnu.org
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <20200311103004.7649-3-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

block/backup.c

@@ -57,15 +57,6 @@ static void backup_progress_bytes_callback(int64_t bytes, void *opaque)
     BackupBlockJob *s = opaque;
 
     s->bytes_read += bytes;
-    job_progress_update(&s->common.job, bytes);
-}
-
-static void backup_progress_reset_callback(void *opaque)
-{
-    BackupBlockJob *s = opaque;
-    uint64_t estimate = bdrv_get_dirty_count(s->bcs->copy_bitmap);
-
-    job_progress_set_remaining(&s->common.job, estimate);
 }
 
 static int coroutine_fn backup_do_cow(BackupBlockJob *job,
@@ -464,8 +455,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     job->cluster_size = cluster_size;
     job->len = len;
 
-    block_copy_set_callbacks(bcs, backup_progress_bytes_callback,
+    block_copy_set_progress_callback(bcs, backup_progress_bytes_callback, job);
-                             backup_progress_reset_callback, job);
+    block_copy_set_progress_meter(bcs, &job->common.job.progress);
 
     /* Required permissions are already taken by backup-top target */
     block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL,

block/block-copy.c

@@ -127,17 +127,20 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
     return s;
 }
 
-void block_copy_set_callbacks(
+void block_copy_set_progress_callback(
         BlockCopyState *s,
         ProgressBytesCallbackFunc progress_bytes_callback,
-        ProgressResetCallbackFunc progress_reset_callback,
         void *progress_opaque)
 {
     s->progress_bytes_callback = progress_bytes_callback;
-    s->progress_reset_callback = progress_reset_callback;
     s->progress_opaque = progress_opaque;
 }
 
+void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm)
+{
+    s->progress = pm;
+}
+
 /*
  * block_copy_do_copy
  *
@@ -269,7 +272,9 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
 
     if (!ret) {
         bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
-        s->progress_reset_callback(s->progress_opaque);
+        progress_set_remaining(s->progress,
+                               bdrv_get_dirty_count(s->copy_bitmap) +
+                               s->in_flight_bytes);
     }
 
     *count = bytes;
@@ -331,15 +336,18 @@ int coroutine_fn block_copy(BlockCopyState *s,
         trace_block_copy_process(s, start);
 
         bdrv_reset_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
+        s->in_flight_bytes += chunk_end - start;
 
         co_get_from_shres(s->mem, chunk_end - start);
         ret = block_copy_do_copy(s, start, chunk_end, error_is_read);
         co_put_to_shres(s->mem, chunk_end - start);
+        s->in_flight_bytes -= chunk_end - start;
         if (ret < 0) {
             bdrv_set_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
             break;
         }
 
+        progress_work_done(s->progress, chunk_end - start);
         s->progress_bytes_callback(chunk_end - start, s->progress_opaque);
         start = chunk_end;
         ret = 0;

include/block/block-copy.h

@@ -26,7 +26,6 @@ typedef struct BlockCopyInFlightReq {
 } BlockCopyInFlightReq;
 
 typedef void (*ProgressBytesCallbackFunc)(int64_t bytes, void *opaque);
-typedef void (*ProgressResetCallbackFunc)(void *opaque);
 typedef struct BlockCopyState {
     /*
      * BdrvChild objects are not owned or managed by block-copy. They are
@@ -36,6 +35,7 @@ typedef struct BlockCopyState {
     BdrvChild *source;
     BdrvChild *target;
     BdrvDirtyBitmap *copy_bitmap;
+    int64_t in_flight_bytes;
     int64_t cluster_size;
     bool use_copy_range;
     int64_t copy_size;
@@ -60,15 +60,9 @@ typedef struct BlockCopyState {
      */
     bool skip_unallocated;
 
+    ProgressMeter *progress;
     /* progress_bytes_callback: called when some copying progress is done. */
     ProgressBytesCallbackFunc progress_bytes_callback;
-
-    /*
-     * progress_reset_callback: called when some bytes reset from copy_bitmap
-     * (see @skip_unallocated above). The callee is assumed to recalculate how
-     * many bytes remain based on the dirty bit count of copy_bitmap.
-     */
-    ProgressResetCallbackFunc progress_reset_callback;
     void *progress_opaque;
 
     SharedResource *mem;
@@ -79,12 +73,13 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
                                      BdrvRequestFlags write_flags,
                                      Error **errp);
 
-void block_copy_set_callbacks(
+void block_copy_set_progress_callback(
         BlockCopyState *s,
         ProgressBytesCallbackFunc progress_bytes_callback,
-        ProgressResetCallbackFunc progress_reset_callback,
         void *progress_opaque);
 
+void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm);
+
 void block_copy_state_free(BlockCopyState *s);
 
 int64_t block_copy_reset_unallocated(BlockCopyState *s,