block: Add errp to b{lk,drv}_truncate()

For one thing, this allows us to drop the error message generation from
qemu-img.c and blockdev.c and instead have it unified in
bdrv_truncate().

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170328205129.15138-3-mreitz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/block.c b/block.c
index 7b557f3..6a1937e 100644
--- a/block.c
+++ b/block.c
@@ -3307,7 +3307,7 @@ exit:
 /**
  * Truncate file to 'offset' bytes (needed only for file protocols)
  */
-int bdrv_truncate(BdrvChild *child, int64_t offset)
+int bdrv_truncate(BdrvChild *child, int64_t offset, Error **errp)
 {
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
@@ -3315,12 +3315,18 @@ int bdrv_truncate(BdrvChild *child, int64_t offset)
 
     assert(child->perm & BLK_PERM_RESIZE);
 
-    if (!drv)
+    if (!drv) {
+        error_setg(errp, "No medium inserted");
         return -ENOMEDIUM;
-    if (!drv->bdrv_truncate)
+    }
+    if (!drv->bdrv_truncate) {
+        error_setg(errp, "Image format driver does not support resize");
         return -ENOTSUP;
-    if (bs->read_only)
+    }
+    if (bs->read_only) {
+        error_setg(errp, "Image is read-only");
         return -EACCES;
+    }
 
     ret = drv->bdrv_truncate(bs, offset);
     if (ret == 0) {
@@ -3328,6 +3334,8 @@ int bdrv_truncate(BdrvChild *child, int64_t offset)
         bdrv_dirty_bitmap_truncate(bs);
         bdrv_parent_cb_resize(bs);
         ++bs->write_gen;
+    } else {
+        error_setg_errno(errp, -ret, "Failed to resize image");
     }
     return ret;
 }