[PATCH v2] migration/channel-block: fix return value for qio_channel_block_{readv, writev}

[Fiona Ebner]

in the error case. The documentation in include/io/channel.h states
that -1 or QIO_CHANNEL_ERR_BLOCK should be returned upon error. Simply
passing along the return value from the bdrv-functions has the
potential to confuse the call sides. Non-blocking mode is not
implemented currently, so -1 it is.

Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
---

v1 -> v2:
    * Use error_setg_errno() instead of error_setg().
    * Use "failed" instead of "returned error" in error message. Now
      that no numerical error code is used, this sounds a bit nicer
      IMHO.

 migration/channel-block.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/migration/channel-block.c b/migration/channel-block.c
index c55c8c93ce..f4ab53acdb 100644
--- a/migration/channel-block.c
+++ b/migration/channel-block.c
@@ -62,7 +62,8 @@ qio_channel_block_readv(QIOChannel *ioc,
     qemu_iovec_init_external(&qiov, (struct iovec *)iov, niov);
     ret = bdrv_readv_vmstate(bioc->bs, &qiov, bioc->offset);
     if (ret < 0) {
-        return ret;
+        error_setg_errno(errp, -ret, "bdrv_readv_vmstate failed");
+        return -1;
     }
 
     bioc->offset += qiov.size;
@@ -86,7 +87,8 @@ qio_channel_block_writev(QIOChannel *ioc,
     qemu_iovec_init_external(&qiov, (struct iovec *)iov, niov);
     ret = bdrv_writev_vmstate(bioc->bs, &qiov, bioc->offset);
     if (ret < 0) {
-        return ret;
+        error_setg_errno(errp, -ret, "bdrv_writev_vmstate failed");
+        return -1;
     }
 
     bioc->offset += qiov.size;
-- 
2.30.2