Re: [Qemu-block] [Qemu-devel] [PATCH for-2.11] nbd/client: Use error_prepend() correctly

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> When using error prepend(), it is necessary to end with a space
> in the format string; otherwise, messages come out incorrectly,
> such as when connecting to a socket that hangs up immediately:
>
> can't open device nbd://localhost:10809/: Failed to read dataUnexpected 
> end-of-file before all bytes were read
>
> Originally botched in commit e44ed99d, then several more instances
> added in the meantime.
>
> CC: address@hidden
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  nbd/client.c | 50 ++++++++++++++++++++++++++------------------------
>  1 file changed, 26 insertions(+), 24 deletions(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index 1880103d2a..4e15fc484d 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -79,12 +79,12 @@ static int nbd_send_option_request(QIOChannel *ioc, 
> uint32_t opt,
>      stl_be_p(&req.length, len);
>
>      if (nbd_write(ioc, &req, sizeof(req), errp) < 0) {
> -        error_prepend(errp, "Failed to send option request header");
> +        error_prepend(errp, "Failed to send option request header: ");
>          return -1;
>      }
>
>      if (len && nbd_write(ioc, (char *) data, len, errp) < 0) {
> -        error_prepend(errp, "Failed to send option request data");
> +        error_prepend(errp, "Failed to send option request data: ");
>          return -1;
>      }
>
> @@ -113,7 +113,7 @@ static int nbd_receive_option_reply(QIOChannel *ioc, 
> uint32_t opt,
>  {
>      QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
>      if (nbd_read(ioc, reply, sizeof(*reply), errp) < 0) {
> -        error_prepend(errp, "failed to read option reply");
> +        error_prepend(errp, "failed to read option reply: ");
>          nbd_send_opt_abort(ioc);
>          return -1;
>      }

Preexisting: inconsistent capitalization (Failed vs. failed).

In general, prepend chains looks slightly less ugly when each link
starts with a lower case letter.  Compare:

    can't open device nbd://localhost:10809/: failed to read data: unexpected 
end-of-file before all bytes were read
    Can't open device nbd://localhost:10809/: Failed to read data: Unexpected 
end-of-file before all bytes were read

Neither message is really good, but the second one is ugly to boot.

> @@ -166,7 +166,7 @@ static int nbd_handle_reply_err(QIOChannel *ioc, 
> nbd_opt_reply *reply,
>          msg = g_malloc(reply->length + 1);
>          if (nbd_read(ioc, msg, reply->length, errp) < 0) {
>              error_prepend(errp, "failed to read option error 0x%" PRIx32
> -                          " (%s) message",
> +                          " (%s) message: ",
>                            reply->type, nbd_rep_lookup(reply->type));
>              goto cleanup;
>          }
> @@ -277,7 +277,7 @@ static int nbd_receive_list(QIOChannel *ioc, const char 
> *want, bool *match,
>          return -1;
>      }
>      if (nbd_read(ioc, &namelen, sizeof(namelen), errp) < 0) {
> -        error_prepend(errp, "failed to read option name length");
> +        error_prepend(errp, "failed to read option name length: ");
>          nbd_send_opt_abort(ioc);
>          return -1;
>      }
> @@ -290,7 +290,8 @@ static int nbd_receive_list(QIOChannel *ioc, const char 
> *want, bool *match,
>      }
>      if (namelen != strlen(want)) {
>          if (nbd_drop(ioc, len, errp) < 0) {
> -            error_prepend(errp, "failed to skip export name with wrong 
> length");
> +            error_prepend(errp,
> +                          "failed to skip export name with wrong length: ");
>              nbd_send_opt_abort(ioc);
>              return -1;
>          }
> @@ -299,14 +300,14 @@ static int nbd_receive_list(QIOChannel *ioc, const char 
> *want, bool *match,
>
>      assert(namelen < sizeof(name));
>      if (nbd_read(ioc, name, namelen, errp) < 0) {
> -        error_prepend(errp, "failed to read export name");
> +        error_prepend(errp, "failed to read export name: ");
>          nbd_send_opt_abort(ioc);
>          return -1;
>      }
>      name[namelen] = '\0';
>      len -= namelen;
>      if (nbd_drop(ioc, len, errp) < 0) {
> -        error_prepend(errp, "failed to read export description");
> +        error_prepend(errp, "failed to read export description: ");
>          nbd_send_opt_abort(ioc);
>          return -1;
>      }
> @@ -390,7 +391,7 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>              return -1;
>          }
>          if (nbd_read(ioc, &type, sizeof(type), errp) < 0) {
> -            error_prepend(errp, "failed to read info type");
> +            error_prepend(errp, "failed to read info type: ");
>              nbd_send_opt_abort(ioc);
>              return -1;
>          }
> @@ -405,13 +406,13 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>                  return -1;
>              }
>              if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
> -                error_prepend(errp, "failed to read info size");
> +                error_prepend(errp, "failed to read info size: ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
>              be64_to_cpus(&info->size);
>              if (nbd_read(ioc, &info->flags, sizeof(info->flags), errp) < 0) {
> -                error_prepend(errp, "failed to read info flags");
> +                error_prepend(errp, "failed to read info flags: ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
> @@ -428,7 +429,7 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>              }
>              if (nbd_read(ioc, &info->min_block, sizeof(info->min_block),
>                           errp) < 0) {
> -                error_prepend(errp, "failed to read info minimum block 
> size");
> +                error_prepend(errp, "failed to read info minimum block size: 
> ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
> @@ -441,7 +442,8 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>              }
>              if (nbd_read(ioc, &info->opt_block, sizeof(info->opt_block),
>                           errp) < 0) {
> -                error_prepend(errp, "failed to read info preferred block 
> size");
> +                error_prepend(errp,
> +                              "failed to read info preferred block size: ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
> @@ -455,7 +457,7 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>              }
>              if (nbd_read(ioc, &info->max_block, sizeof(info->max_block),
>                           errp) < 0) {
> -                error_prepend(errp, "failed to read info maximum block 
> size");
> +                error_prepend(errp, "failed to read info maximum block size: 
> ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
> @@ -467,7 +469,7 @@ static int nbd_opt_go(QIOChannel *ioc, const char 
> *wantname,
>          default:
>              trace_nbd_opt_go_info_unknown(type, nbd_info_lookup(type));
>              if (nbd_drop(ioc, len, errp) < 0) {
> -                error_prepend(errp, "Failed to read info payload");
> +                error_prepend(errp, "Failed to read info payload: ");
>                  nbd_send_opt_abort(ioc);
>                  return -1;
>              }
> @@ -618,7 +620,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>      }
>
>      if (nbd_read(ioc, buf, 8, errp) < 0) {
> -        error_prepend(errp, "Failed to read data");
> +        error_prepend(errp, "Failed to read data: ");
>          goto fail;
>      }
>
> @@ -637,7 +639,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>      }
>
>      if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
> -        error_prepend(errp, "Failed to read magic");
> +        error_prepend(errp, "Failed to read magic: ");
>          goto fail;
>      }
>      magic = be64_to_cpu(magic);
> @@ -649,7 +651,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>          bool fixedNewStyle = false;
>
>          if (nbd_read(ioc, &globalflags, sizeof(globalflags), errp) < 0) {
> -            error_prepend(errp, "Failed to read server flags");
> +            error_prepend(errp, "Failed to read server flags: ");
>              goto fail;
>          }
>          globalflags = be16_to_cpu(globalflags);
> @@ -665,7 +667,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>          /* client requested flags */
>          clientflags = cpu_to_be32(clientflags);
>          if (nbd_write(ioc, &clientflags, sizeof(clientflags), errp) < 0) {
> -            error_prepend(errp, "Failed to send clientflags field");
> +            error_prepend(errp, "Failed to send clientflags field: ");
>              goto fail;
>          }
>          if (tlscreds) {
> @@ -727,13 +729,13 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>
>          /* Read the response */
>          if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
> -            error_prepend(errp, "Failed to read export length");
> +            error_prepend(errp, "Failed to read export length: ");
>              goto fail;
>          }
>          be64_to_cpus(&info->size);
>
>          if (nbd_read(ioc, &info->flags, sizeof(info->flags), errp) < 0) {
> -            error_prepend(errp, "Failed to read export flags");
> +            error_prepend(errp, "Failed to read export flags: ");
>              goto fail;
>          }
>          be16_to_cpus(&info->flags);
> @@ -750,13 +752,13 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>          }
>
>          if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
> -            error_prepend(errp, "Failed to read export length");
> +            error_prepend(errp, "Failed to read export length: ");
>              goto fail;
>          }
>          be64_to_cpus(&info->size);
>
>          if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
> -            error_prepend(errp, "Failed to read export flags");
> +            error_prepend(errp, "Failed to read export flags: ");
>              goto fail;
>          }
>          be32_to_cpus(&oldflags);
> @@ -772,7 +774,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char 
> *name,
>
>      trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
>      if (zeroes && nbd_drop(ioc, 124, errp) < 0) {
> -        error_prepend(errp, "Failed to read reserved block");
> +        error_prepend(errp, "Failed to read reserved block: ");
>          goto fail;
>      }
>      rc = 0;

Reviewed-by: Markus Armbruster <address@hidden>