[Qemu-devel] [PATCH] block: Don't throw away errno via error_setg

[Jeff Cody <jcody@redhat.com>]

There are a handful of places in the block layer where a failure path
has a valid -errno value, yet error_setg() is used.  Those instances
should instead use error_setg_errno(), to preserve as much error
information as possible.

This patch replaces those instances with error_setg_errno(), so that
errno is passed up the stack in the error message.

Reported-By: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/mirror.c         | 13 +++++++++----
 block/qcow2-snapshot.c |  8 +++++---
 block/vmdk.c           |  6 +++---
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 41bb83c..b31d840 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -633,6 +633,7 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
 {
     int64_t length, base_length;
     int orig_base_flags;
+    int ret;
 
     assert(errp != NULL);
 
@@ -644,19 +645,23 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
 
     length = bdrv_getlength(bs);
     if (length < 0) {
-        error_setg(errp, "Unable to determine length of %s", bs->filename);
+        error_setg_errno(errp, -length,
+                         "Unable to determine length of %s", bs->filename);
         goto error_restore_flags;
     }
 
     base_length = bdrv_getlength(base);
     if (base_length < 0) {
-        error_setg(errp, "Unable to determine length of %s", base->filename);
+        error_setg_errno(errp, -base_length,
+                         "Unable to determine length of %s", base->filename);
         goto error_restore_flags;
     }
 
     if (length > base_length) {
-        if (bdrv_truncate(base, length) < 0) {
-            error_setg(errp, "Top image %s is larger than base image %s, and "
+        ret = bdrv_truncate(base, length);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret,
+                            "Top image %s is larger than base image %s, and "
                              "resize of base image failed",
                              bs->filename, base->filename);
             goto error_restore_flags;
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index ad8bf3d..2fc6320 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -606,7 +606,8 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
     s->nb_snapshots--;
     ret = qcow2_write_snapshots(bs);
     if (ret < 0) {
-        error_setg(errp, "Failed to remove snapshot from snapshot list");
+        error_setg_errno(errp, -ret,
+                         "Failed to remove snapshot from snapshot list");
         return ret;
     }
 
@@ -624,7 +625,7 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
     ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset,
                                          sn.l1_size, -1);
     if (ret < 0) {
-        error_setg(errp, "Failed to free the cluster and L1 table");
+        error_setg_errno(errp, -ret, "Failed to free the cluster and L1 table");
         return ret;
     }
     qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t),
@@ -633,7 +634,8 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
     /* must update the copied flag on the current cluster offsets */
     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
     if (ret < 0) {
-        error_setg(errp, "Failed to update snapshot status in disk");
+        error_setg_errno(errp, -ret,
+                         "Failed to update snapshot status in disk");
         return ret;
     }
 
diff --git a/block/vmdk.c b/block/vmdk.c
index e809e2e..ff6f5ee 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1502,7 +1502,7 @@ static int vmdk_create_extent(const char *filename, int64_t filesize,
     if (flat) {
         ret = bdrv_truncate(bs, filesize);
         if (ret < 0) {
-            error_setg(errp, "Could not truncate file");
+            error_setg_errno(errp, -ret, "Could not truncate file");
         }
         goto exit;
     }
@@ -1562,7 +1562,7 @@ static int vmdk_create_extent(const char *filename, int64_t filesize,
 
     ret = bdrv_truncate(bs, le64_to_cpu(header.grain_offset) << 9);
     if (ret < 0) {
-        error_setg(errp, "Could not truncate file");
+        error_setg_errno(errp, -ret, "Could not truncate file");
         goto exit;
     }
 
@@ -1846,7 +1846,7 @@ static int vmdk_create(const char *filename, QEMUOptionParameter *options,
     if (desc_offset == 0) {
         ret = bdrv_truncate(new_bs, desc_len);
         if (ret < 0) {
-            error_setg(errp, "Could not truncate file");
+            error_setg_errno(errp, -ret, "Could not truncate file");
         }
     }
 exit:
-- 
1.8.3.1