[RFC 02/24] block/block-copy: use block_status

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

Use bdrv_block_status_above to chose effective chunk size and to handle
zeroes effectively.

This substitutes checking for just being allocated or not, and drops
old code path for it. Assistance by backup job is dropped too, as
caching block-status information is more difficult than just caching
is-allocated information in our dirty bitmap, and backup job is not
good place for this caching anyway.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/block-copy.c | 67 +++++++++++++++++++++++++++++++++++++---------
 block/trace-events |  1 +
 2 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/block/block-copy.c b/block/block-copy.c
index 8602e2cae7..74295d93d5 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -152,7 +152,7 @@ void block_copy_set_callbacks(
  */
 static int coroutine_fn block_copy_do_copy(BlockCopyState *s,
                                            int64_t start, int64_t end,
-                                           bool *error_is_read)
+                                           bool zeroes, bool *error_is_read)
 {
     int ret;
     int nbytes = MIN(end, s->len) - start;
@@ -162,6 +162,18 @@ static int coroutine_fn block_copy_do_copy(BlockCopyState *s,
     assert(QEMU_IS_ALIGNED(end, s->cluster_size));
     assert(end < s->len || end == QEMU_ALIGN_UP(s->len, s->cluster_size));
 
+    if (zeroes) {
+        ret = bdrv_co_pwrite_zeroes(s->target, start, nbytes, s->write_flags &
+                                    ~BDRV_REQ_WRITE_COMPRESSED);
+        if (ret < 0) {
+            trace_block_copy_write_zeroes_fail(s, start, ret);
+            if (error_is_read) {
+                *error_is_read = false;
+            }
+        }
+        return ret;
+    }
+
     if (s->use_copy_range) {
         ret = bdrv_co_copy_range(s->source, start, s->target, start, nbytes,
                                  0, s->write_flags);
@@ -225,6 +237,34 @@ out:
     return ret;
 }
 
+static int block_copy_block_status(BlockCopyState *s, int64_t offset,
+                                   int64_t bytes, int64_t *pnum)
+{
+    int64_t num;
+    BlockDriverState *base;
+    int ret;
+
+    if (s->skip_unallocated && s->source->bs->backing) {
+        base = s->source->bs->backing->bs;
+    } else {
+        base = NULL;
+    }
+
+    ret = bdrv_block_status_above(s->source->bs, base, offset, bytes, &num,
+                                  NULL, NULL);
+    if (ret < 0 || num < s->cluster_size) {
+        num = s->cluster_size;
+        ret = BDRV_BLOCK_ALLOCATED | BDRV_BLOCK_DATA;
+    } else if (offset + num == s->len) {
+        num = QEMU_ALIGN_UP(num, s->cluster_size);
+    } else {
+        num = QEMU_ALIGN_DOWN(num, s->cluster_size);
+    }
+
+    *pnum = num;
+    return ret;
+}
+
 /*
  * Check if the cluster starting at offset is allocated or not.
  * return via pnum the number of contiguous clusters sharing this allocation.
@@ -301,7 +341,6 @@ int coroutine_fn block_copy(BlockCopyState *s,
 {
     int ret = 0;
     int64_t end = bytes + start; /* bytes */
-    int64_t status_bytes;
     BlockCopyInFlightReq req;
 
     /*
@@ -318,7 +357,7 @@ int coroutine_fn block_copy(BlockCopyState *s,
     block_copy_inflight_req_begin(s, &req, start, end);
 
     while (start < end) {
-        int64_t next_zero, chunk_end;
+        int64_t next_zero, chunk_end, status_bytes;
 
         if (!bdrv_dirty_bitmap_get(s->copy_bitmap, start)) {
             trace_block_copy_skip(s, start);
@@ -336,23 +375,25 @@ int coroutine_fn block_copy(BlockCopyState *s,
             chunk_end = next_zero;
         }
 
-        if (s->skip_unallocated) {
-            ret = block_copy_reset_unallocated(s, start, &status_bytes);
-            if (ret == 0) {
-                trace_block_copy_skip_range(s, start, status_bytes);
-                start += status_bytes;
-                continue;
-            }
-            /* Clamp to known allocated region */
-            chunk_end = MIN(chunk_end, start + status_bytes);
+        ret = block_copy_block_status(s, start, chunk_end - start,
+                                      &status_bytes);
+        if (s->skip_unallocated && !(ret & BDRV_BLOCK_ALLOCATED)) {
+            bdrv_reset_dirty_bitmap(s->copy_bitmap, start, status_bytes);
+            s->progress_reset_callback(s->progress_opaque);
+            trace_block_copy_skip_range(s, start, status_bytes);
+            start += status_bytes;
+            continue;
         }
 
+        chunk_end = MIN(chunk_end, start + status_bytes);
+
         trace_block_copy_process(s, start);
 
         bdrv_reset_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
 
         co_get_from_shres(s->mem, chunk_end - start);
-        ret = block_copy_do_copy(s, start, chunk_end, error_is_read);
+        ret = block_copy_do_copy(s, start, chunk_end, ret & BDRV_BLOCK_ZERO,
+                                 error_is_read);
         co_put_to_shres(s->mem, chunk_end - start);
         if (ret < 0) {
             bdrv_set_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
diff --git a/block/trace-events b/block/trace-events
index 6ba86decca..346537a1d2 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -48,6 +48,7 @@ block_copy_process(void *bcs, int64_t start) "bcs %p start %"PRId64
 block_copy_copy_range_fail(void *bcs, int64_t start, int ret) "bcs %p start %"PRId64" ret %d"
 block_copy_read_fail(void *bcs, int64_t start, int ret) "bcs %p start %"PRId64" ret %d"
 block_copy_write_fail(void *bcs, int64_t start, int ret) "bcs %p start %"PRId64" ret %d"
+block_copy_write_zeroes_fail(void *bcs, int64_t start, int ret) "bcs %p start %"PRId64" ret %d"
 
 # ../blockdev.c
 qmp_block_job_cancel(void *job) "job %p"
-- 
2.21.0