Re: [PATCH v3 3/5] block: refactor error handling of commit_iteration

[Vladimir Sementsov-Ogievskiy]

On 01.09.24 17:24, Vincent Vanlaer wrote:
Signed-off-by: Vincent Vanlaer <libvirt-e6954...@volkihar.be>
---
  block/commit.c | 37 ++++++++++++++++++++++---------------
  1 file changed, 22 insertions(+), 15 deletions(-)
diff --git a/block/commit.c b/block/commit.c
index 9eedd1fa47..288e413be3 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -130,7 +130,6 @@ static void commit_clean(Job *job)
  
  static int commit_iteration(CommitBlockJob *s, int64_t offset, int64_t *n, void *buf) {
      int ret = 0;
-    bool copy;
      bool error_in_source = true;
  
      /* Copy if allocated above the base */
@@ -140,19 +139,34 @@ static int commit_iteration(CommitBlockJob *s, int64_t 
offset, int64_t *n, void
              n, NULL, NULL, NULL);
      }
  
-    copy = (ret >= 0 && ret & BDRV_BLOCK_ALLOCATED);
+    if (ret < 0) {
+        goto handle_error;
+    }
+
      trace_commit_one_iteration(s, offset, *n, ret);

this way we loose trace point for error case. Let's move trace_... above "if 
(ret.."

-    if (copy) {
+
+    if (ret & BDRV_BLOCK_ALLOCATED) {
          assert(*n < SIZE_MAX);
  
          ret = blk_co_pread(s->top, offset, *n, buf, 0);
-        if (ret >= 0) {
-            ret = blk_co_pwrite(s->base, offset, *n, buf, 0);
-            if (ret < 0) {
-                error_in_source = false;
-            }
+        if (ret < 0) {
+            goto handle_error;
          }
+
+        ret = blk_co_pwrite(s->base, offset, *n, buf, 0);
+        if (ret < 0) {
+            error_in_source = false;
+            goto handle_error;
+        }
+
+        block_job_ratelimit_processed_bytes(&s->common, *n);
      }
+
+    /* Publish progress */
+
+    job_progress_update(&s->common.job, *n);
+

it looks a bit strange to fallthrough to "handle_error" from success path


I suggest:

@@ -166,17 +166,17 @@ static int commit_iteration(CommitBlockJob *s, int64_t 
offset, int64_t *n, void
 
     job_progress_update(&s->common.job, *n);
 
-handle_error:
-    if (ret < 0) {
-        BlockErrorAction action = block_job_error_action(&s->common, 
s->on_error,
-                                                         error_in_source, 
-ret);
-        if (action == BLOCK_ERROR_ACTION_REPORT) {
-            return ret;
-        } else {
-            *n = 0;
-        }
+    return 0;
+
+fail:
+    BlockErrorAction action = block_job_error_action(&s->common, s->on_error,
+                                                     error_in_source, -ret);
+    if (action == BLOCK_ERROR_ACTION_REPORT) {
+        return ret;
     }
 
+    /* Retry iteration */
+    *n = 0;
     return 0;
 }



(also, "fail" name is more popular for such labels:
$ git grep 'goto fail' | wc -l
1334
)



+handle_error:
      if (ret < 0) {
          BlockErrorAction action = block_job_error_action(&s->common, 
s->on_error,
                                                           error_in_source, 
-ret);
@@ -160,15 +174,8 @@ static int commit_iteration(CommitBlockJob *s, int64_t 
offset, int64_t *n, void
              return ret;
          } else {
              *n = 0;
-            return 0;
          }
      }
-    /* Publish progress */
-    job_progress_update(&s->common.job, *n);
-
-    if (copy) {
-        block_job_ratelimit_processed_bytes(&s->common, *n);
-    }
  
      return 0;
  }

--
Best regards,
Vladimir