[Libguestfs] [libnbd PATCH v2 1/5] lib: Refactor state event into command_common

[Richard W.M. Jones]

On Tue, May 21, 2019 at 10:15:48PM -0500, Eric Blake wrote:
> The next patch wants to make queuing commands smarter; rather than
> duplicating the logic at each command's call site, it's better to
> centralize things in command_common, and to also make this helper
> routine visible for use in NBD_CMD_DISC.

There's a few problems with this patch.

To avoid leaking symbols -- even though we have a linker script, not
all future platforms are expected to support it -- global symbols
which are not exported should be called nbd_internal_*.  So
command_common should be nbd_internal_command_common.

The bigger problem is:

> @@ -505,8 +495,5 @@ nbd_unlocked_aio_block_status (struct nbd_connection *conn,
>    cmd->extent_fn = extent;
>    cmd->extent_id = id;
> 
> -  if (nbd_internal_run (conn->h, conn, cmd_issue) == -1)
> -    return -1;
> -
>    return cmd->handle;

This changes the semantics of the function because the cmd->extent_*
fields are set too late.  (Yes, command_common is rather ad hoc :-)

Rich.

-- 
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