Re: [PATCH v2 01/18] migration: Fix file migration with fdset

[Peter Xu <peterx@redhat.com>]

On Thu, May 23, 2024 at 04:05:31PM -0300, Fabiano Rosas wrote:
> When the "file:" migration support was added we missed the special
> case in the qemu_open_old implementation that allows for a particular
> file name format to be used to refer to a set of file descriptors that
> have been previously provided to QEMU via the add-fd QMP command.
> 
> When using this fdset feature, we should not truncate the migration
> file because being given an fd means that the management layer is in
> control of the file and will likely already have some data written to
> it. This is further indicated by the presence of the 'offset'
> argument, which indicates the start of the region where QEMU is
> allowed to write.
> 
> Fix the issue by replacing the O_TRUNC flag on open by an ftruncate
> call, which will take the offset into consideration.
> 
> Fixes: 385f510df5 ("migration: file URI offset")
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Fabiano Rosas <farosas@suse.de>

Reviewed-by: Peter Xu <peterx@redhat.com>

Right below the change, did we forget to free the ioc if
qio_channel_io_seek() failed?

> ---
>  migration/file.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/file.c b/migration/file.c
> index ab18ba505a..ba5b5c44ff 100644
> --- a/migration/file.c
> +++ b/migration/file.c
> @@ -84,12 +84,19 @@ void file_start_outgoing_migration(MigrationState *s,
>  
>      trace_migration_file_outgoing(filename);
>  
> -    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
> -                                     0600, errp);
> +    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY, 0600, errp);
>      if (!fioc) {
>          return;
>      }
>  
> +    if (ftruncate(fioc->fd, offset)) {
> +        error_setg_errno(errp, errno,
> +                         "failed to truncate migration file to offset %" PRIx64,
> +                         offset);
> +        object_unref(OBJECT(fioc));
> +        return;
> +    }
> +
>      outgoing_args.fname = g_strdup(filename);
>  
>      ioc = QIO_CHANNEL(fioc);
> -- 
> 2.35.3
> 

-- 
Peter Xu