[Qemu-devel] [PATCH V4 2/6] qcow2: add error message in qcow2_write_snapshots()

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

The function still returns int since qcow2_snapshot_delete() will
return the number.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
---
 block/qcow2-snapshot.c |   48 ++++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index b373f9a..4bd494b 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -152,7 +152,7 @@ fail:
 }
 
 /* add at the end of the file a new list of snapshots */
-static int qcow2_write_snapshots(BlockDriverState *bs)
+static int qcow2_write_snapshots(BlockDriverState *bs, Error **errp)
 {
     BDRVQcowState *s = bs->opaque;
     QCowSnapshot *sn;
@@ -183,10 +183,18 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
     offset = snapshots_offset;
     if (offset < 0) {
         ret = offset;
+        error_setg(errp,
+                   "Failed in allocation of cluster for snapshot list: "
+                   "%d (%s)",
+                   ret, strerror(-ret));
         goto fail;
     }
     ret = bdrv_flush(bs);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed in flush after snapshot list cluster allocation: "
+                   "%d (%s)",
+                   ret, strerror(-ret));
         goto fail;
     }
 
@@ -194,6 +202,10 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
      * must indeed be completely free */
     ret = qcow2_pre_write_overlap_check(bs, 0, offset, snapshots_size);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed in overlap check for snapshot list cluster at %"
+                   PRIi64 " with size %d: %d (%s)",
+                   offset, snapshots_size, ret, strerror(-ret));
         goto fail;
     }
 
@@ -227,24 +239,40 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
 
         ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));
         if (ret < 0) {
+            error_setg(errp,
+                       "Failed in write of snapshot header at %"
+                       PRIi64 " with size %" PRIu64 ": %d (%s)",
+                       offset, sizeof(h), ret, strerror(-ret));
             goto fail;
         }
         offset += sizeof(h);
 
         ret = bdrv_pwrite(bs->file, offset, &extra, sizeof(extra));
         if (ret < 0) {
+            error_setg(errp,
+                       "Failed in write of extra snapshot data at %"
+                       PRIi64 " with size %" PRIu64 ": %d (%s)",
+                       offset, sizeof(extra), ret, strerror(-ret));
             goto fail;
         }
         offset += sizeof(extra);
 
         ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size);
         if (ret < 0) {
+            error_setg(errp,
+                       "Failed in write of snapshot id string at %"
+                       PRIi64 " with size %d: %d (%s)",
+                       offset, id_str_size, ret, strerror(-ret));
             goto fail;
         }
         offset += id_str_size;
 
         ret = bdrv_pwrite(bs->file, offset, sn->name, name_size);
         if (ret < 0) {
+            error_setg(errp,
+                       "Failed in write of snapshot name string at %"
+                       PRIi64 " with size %d: %d (%s)",
+                       offset, name_size, ret, strerror(-ret));
             goto fail;
         }
         offset += name_size;
@@ -256,6 +284,9 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
      */
     ret = bdrv_flush(bs);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed in flush after snapshot list update: %d (%s)",
+                   ret, strerror(-ret));
         goto fail;
     }
 
@@ -268,6 +299,11 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
     ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
                            &header_data, sizeof(header_data));
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed in update of image header at %"
+                   PRIi64 " with size %" PRIu64 ":%d (%s)",
+                   offsetof(QCowHeader, nb_snapshots), sizeof(header_data),
+                   ret, strerror(-ret));
         goto fail;
     }
 
@@ -283,6 +319,9 @@ fail:
         qcow2_free_clusters(bs, snapshots_offset, snapshots_size,
                             QCOW2_DISCARD_ALWAYS);
     }
+    if (errp) {
+        g_assert(error_is_set(errp));
+    }
     return ret;
 }
 
@@ -446,10 +485,8 @@ void qcow2_snapshot_create(BlockDriverState *bs,
     s->snapshots = new_snapshot_list;
     s->snapshots[s->nb_snapshots++] = *sn;
 
-    ret = qcow2_write_snapshots(bs);
+    ret = qcow2_write_snapshots(bs, errp);
     if (ret < 0) {
-        /* Following line will be replaced with more detailed error later */
-        error_setg(errp, "Failed in write of snapshot");
         g_free(s->snapshots);
         s->snapshots = old_snapshot_list;
         s->nb_snapshots--;
@@ -623,9 +660,8 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
             s->snapshots + snapshot_index + 1,
             (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));
     s->nb_snapshots--;
-    ret = qcow2_write_snapshots(bs);
+    ret = qcow2_write_snapshots(bs, errp);
     if (ret < 0) {
-        error_setg(errp, "Failed to remove snapshot from snapshot list");
         return ret;
     }
 
-- 
1.7.1