Re: [PATCH v2 4/5] migration: Teach QEMUFile to be QIOChannel-aware

[Dr. David Alan Gilbert]

* Peter Xu (peterx@redhat.com) wrote:
> migration uses QIOChannel typed qemufiles.  In follow up patches, we'll need
> the capability to identify this fact, so that we can get the backing 
> QIOChannel
> from a QEMUFile.
> 
> We can also define types for QEMUFile but so far since we only need to be able
> to identify QIOChannel, introduce a boolean which is simpler.
> 
> Introduce another helper qemu_file_get_ioc() to return the ioc backend of a
> qemufile if has_ioc is set.
> 
> No functional change.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>

Yep, one day we'll sort out the block case, but until then

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/qemu-file-channel.c |  4 ++--
>  migration/qemu-file.c         | 17 ++++++++++++++++-
>  migration/qemu-file.h         |  4 +++-
>  migration/ram.c               |  2 +-
>  migration/savevm.c            |  4 ++--
>  5 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/migration/qemu-file-channel.c b/migration/qemu-file-channel.c
> index 867a5ed0c3..2f8b1fcd46 100644
> --- a/migration/qemu-file-channel.c
> +++ b/migration/qemu-file-channel.c
> @@ -187,11 +187,11 @@ static const QEMUFileOps channel_output_ops = {
>  QEMUFile *qemu_fopen_channel_input(QIOChannel *ioc)
>  {
>      object_ref(OBJECT(ioc));
> -    return qemu_fopen_ops(ioc, &channel_input_ops);
> +    return qemu_fopen_ops(ioc, &channel_input_ops, true);
>  }
>  
>  QEMUFile *qemu_fopen_channel_output(QIOChannel *ioc)
>  {
>      object_ref(OBJECT(ioc));
> -    return qemu_fopen_ops(ioc, &channel_output_ops);
> +    return qemu_fopen_ops(ioc, &channel_output_ops, true);
>  }
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 1eacf9e831..6338d8e2ff 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -55,6 +55,8 @@ struct QEMUFile {
>      Error *last_error_obj;
>      /* has the file has been shutdown */
>      bool shutdown;
> +    /* Whether opaque points to a QIOChannel */
> +    bool has_ioc;
>  };
>  
>  /*
> @@ -101,7 +103,7 @@ bool qemu_file_mode_is_not_valid(const char *mode)
>      return false;
>  }
>  
> -QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops)
> +QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops, bool has_ioc)
>  {
>      QEMUFile *f;
>  
> @@ -109,6 +111,7 @@ QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps 
> *ops)
>  
>      f->opaque = opaque;
>      f->ops = ops;
> +    f->has_ioc = has_ioc;
>      return f;
>  }
>  
> @@ -851,3 +854,15 @@ void qemu_file_set_blocking(QEMUFile *f, bool block)
>          f->ops->set_blocking(f->opaque, block, NULL);
>      }
>  }
> +
> +/*
> + * Return the ioc object if it's a migration channel.  Note: it can return 
> NULL
> + * for callers passing in a non-migration qemufile.  E.g. see 
> qemu_fopen_bdrv()
> + * and its usage in e.g. load_snapshot().  So we need to check against NULL
> + * before using it.  If without the check, migration_incoming_state_destroy()
> + * could fail for load_snapshot().
> + */
> +QIOChannel *qemu_file_get_ioc(QEMUFile *file)
> +{
> +    return file->has_ioc ? QIO_CHANNEL(file->opaque) : NULL;
> +}
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index a9b6d6ccb7..3f36d4dc8c 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -27,6 +27,7 @@
>  
>  #include <zlib.h>
>  #include "exec/cpu-common.h"
> +#include "io/channel.h"
>  
>  /* Read a chunk of data from a file at the given position.  The pos argument
>   * can be ignored if the file is only be used for streaming.  The number of
> @@ -119,7 +120,7 @@ typedef struct QEMUFileHooks {
>      QEMURamSaveFunc *save_page;
>  } QEMUFileHooks;
>  
> -QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops);
> +QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops, bool has_ioc);
>  void qemu_file_set_hooks(QEMUFile *f, const QEMUFileHooks *hooks);
>  int qemu_get_fd(QEMUFile *f);
>  int qemu_fclose(QEMUFile *f);
> @@ -179,5 +180,6 @@ void ram_control_load_hook(QEMUFile *f, uint64_t flags, 
> void *data);
>  size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
>                               ram_addr_t offset, size_t size,
>                               uint64_t *bytes_sent);
> +QIOChannel *qemu_file_get_ioc(QEMUFile *file);
>  
>  #endif
> diff --git a/migration/ram.c b/migration/ram.c
> index f728f5072f..08b3cb7a4a 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -550,7 +550,7 @@ static int compress_threads_save_setup(void)
>          /* comp_param[i].file is just used as a dummy buffer to save data,
>           * set its ops to empty.
>           */
> -        comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops);
> +        comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops, false);
>          comp_param[i].done = true;
>          comp_param[i].quit = false;
>          qemu_mutex_init(&comp_param[i].mutex);
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 72848b946c..96b5e5d639 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -168,9 +168,9 @@ static const QEMUFileOps bdrv_write_ops = {
>  static QEMUFile *qemu_fopen_bdrv(BlockDriverState *bs, int is_writable)
>  {
>      if (is_writable) {
> -        return qemu_fopen_ops(bs, &bdrv_write_ops);
> +        return qemu_fopen_ops(bs, &bdrv_write_ops, false);
>      }
> -    return qemu_fopen_ops(bs, &bdrv_read_ops);
> +    return qemu_fopen_ops(bs, &bdrv_read_ops, false);
>  }
>  
>  
> -- 
> 2.31.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK