Re: [Qemu-devel] [PATCH 1/3] nbd: Drop BDS backpointer

[Paolo Bonzini]

On 02/02/2015 22:40, Max Reitz wrote:
> Before this patch, the "opaque" pointer in an NBD BDS points to a
> BDRVNBDState, which contains an NbdClientSession object, which in turn
> contains a pointer to the BDS. This pointer may become invalid due to
> bdrv_swap(), so drop it, and instead pass the BDS directly to the
> nbd-client.c functions which then retrieve the NbdClientSession object
> from there.

Looks good, but please change function names from nbd_client_session_foo
to nbd_client_foo or even just nbd_foo if they do not take an
NbdClientSession* as the first parameter.

Thanks,

Paolo

> Signed-off-by: Max Reitz <address@hidden>
> ---
>  block/nbd-client.c | 95 
> ++++++++++++++++++++++++++++--------------------------
>  block/nbd-client.h | 20 ++++++------
>  block/nbd.c        | 37 ++++++++-------------
>  3 files changed, 73 insertions(+), 79 deletions(-)
> 
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index 28bfb62..4ede714 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -43,20 +43,23 @@ static void 
> nbd_recv_coroutines_enter_all(NbdClientSession *s)
>      }
>  }
>  
> -static void nbd_teardown_connection(NbdClientSession *client)
> +static void nbd_teardown_connection(BlockDriverState *bs)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
> +
>      /* finish any pending coroutines */
>      shutdown(client->sock, 2);
>      nbd_recv_coroutines_enter_all(client);
>  
> -    nbd_client_session_detach_aio_context(client);
> +    nbd_client_session_detach_aio_context(bs);
>      closesocket(client->sock);
>      client->sock = -1;
>  }
>  
>  static void nbd_reply_ready(void *opaque)
>  {
> -    NbdClientSession *s = opaque;
> +    BlockDriverState *bs = opaque;
> +    NbdClientSession *s = nbd_get_client_session(bs);
>      uint64_t i;
>      int ret;
>  
> @@ -89,28 +92,29 @@ static void nbd_reply_ready(void *opaque)
>      }
>  
>  fail:
> -    nbd_teardown_connection(s);
> +    nbd_teardown_connection(bs);
>  }
>  
>  static void nbd_restart_write(void *opaque)
>  {
> -    NbdClientSession *s = opaque;
> +    BlockDriverState *bs = opaque;
>  
> -    qemu_coroutine_enter(s->send_coroutine, NULL);
> +    qemu_coroutine_enter(nbd_get_client_session(bs)->send_coroutine, NULL);
>  }
>  
> -static int nbd_co_send_request(NbdClientSession *s,
> -    struct nbd_request *request,
> -    QEMUIOVector *qiov, int offset)
> +static int nbd_co_send_request(BlockDriverState *bs,
> +                               struct nbd_request *request,
> +                               QEMUIOVector *qiov, int offset)
>  {
> +    NbdClientSession *s = nbd_get_client_session(bs);
>      AioContext *aio_context;
>      int rc, ret;
>  
>      qemu_co_mutex_lock(&s->send_mutex);
>      s->send_coroutine = qemu_coroutine_self();
> -    aio_context = bdrv_get_aio_context(s->bs);
> +    aio_context = bdrv_get_aio_context(bs);
>      aio_set_fd_handler(aio_context, s->sock,
> -                       nbd_reply_ready, nbd_restart_write, s);
> +                       nbd_reply_ready, nbd_restart_write, bs);
>      if (qiov) {
>          if (!s->is_unix) {
>              socket_set_cork(s->sock, 1);
> @@ -129,7 +133,7 @@ static int nbd_co_send_request(NbdClientSession *s,
>      } else {
>          rc = nbd_send_request(s->sock, request);
>      }
> -    aio_set_fd_handler(aio_context, s->sock, nbd_reply_ready, NULL, s);
> +    aio_set_fd_handler(aio_context, s->sock, nbd_reply_ready, NULL, bs);
>      s->send_coroutine = NULL;
>      qemu_co_mutex_unlock(&s->send_mutex);
>      return rc;
> @@ -195,10 +199,11 @@ static void nbd_coroutine_end(NbdClientSession *s,
>      }
>  }
>  
> -static int nbd_co_readv_1(NbdClientSession *client, int64_t sector_num,
> +static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
>                            int nb_sectors, QEMUIOVector *qiov,
>                            int offset)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      struct nbd_request request = { .type = NBD_CMD_READ };
>      struct nbd_reply reply;
>      ssize_t ret;
> @@ -207,7 +212,7 @@ static int nbd_co_readv_1(NbdClientSession *client, 
> int64_t sector_num,
>      request.len = nb_sectors * 512;
>  
>      nbd_coroutine_start(client, &request);
> -    ret = nbd_co_send_request(client, &request, NULL, 0);
> +    ret = nbd_co_send_request(bs, &request, NULL, 0);
>      if (ret < 0) {
>          reply.error = -ret;
>      } else {
> @@ -218,15 +223,16 @@ static int nbd_co_readv_1(NbdClientSession *client, 
> int64_t sector_num,
>  
>  }
>  
> -static int nbd_co_writev_1(NbdClientSession *client, int64_t sector_num,
> +static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
>                             int nb_sectors, QEMUIOVector *qiov,
>                             int offset)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      struct nbd_request request = { .type = NBD_CMD_WRITE };
>      struct nbd_reply reply;
>      ssize_t ret;
>  
> -    if (!bdrv_enable_write_cache(client->bs) &&
> +    if (!bdrv_enable_write_cache(bs) &&
>          (client->nbdflags & NBD_FLAG_SEND_FUA)) {
>          request.type |= NBD_CMD_FLAG_FUA;
>      }
> @@ -235,7 +241,7 @@ static int nbd_co_writev_1(NbdClientSession *client, 
> int64_t sector_num,
>      request.len = nb_sectors * 512;
>  
>      nbd_coroutine_start(client, &request);
> -    ret = nbd_co_send_request(client, &request, qiov, offset);
> +    ret = nbd_co_send_request(bs, &request, qiov, offset);
>      if (ret < 0) {
>          reply.error = -ret;
>      } else {
> @@ -249,14 +255,13 @@ static int nbd_co_writev_1(NbdClientSession *client, 
> int64_t sector_num,
>   * remain aligned to 4K. */
>  #define NBD_MAX_SECTORS 2040
>  
> -int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
> -    int nb_sectors, QEMUIOVector *qiov)
> +int nbd_client_session_co_readv(BlockDriverState *bs, int64_t sector_num,
> +                                int nb_sectors, QEMUIOVector *qiov)
>  {
>      int offset = 0;
>      int ret;
>      while (nb_sectors > NBD_MAX_SECTORS) {
> -        ret = nbd_co_readv_1(client, sector_num,
> -                             NBD_MAX_SECTORS, qiov, offset);
> +        ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
>          if (ret < 0) {
>              return ret;
>          }
> @@ -264,17 +269,16 @@ int nbd_client_session_co_readv(NbdClientSession 
> *client, int64_t sector_num,
>          sector_num += NBD_MAX_SECTORS;
>          nb_sectors -= NBD_MAX_SECTORS;
>      }
> -    return nbd_co_readv_1(client, sector_num, nb_sectors, qiov, offset);
> +    return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
>  }
>  
> -int nbd_client_session_co_writev(NbdClientSession *client, int64_t 
> sector_num,
> +int nbd_client_session_co_writev(BlockDriverState *bs, int64_t sector_num,
>                                   int nb_sectors, QEMUIOVector *qiov)
>  {
>      int offset = 0;
>      int ret;
>      while (nb_sectors > NBD_MAX_SECTORS) {
> -        ret = nbd_co_writev_1(client, sector_num,
> -                              NBD_MAX_SECTORS, qiov, offset);
> +        ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
>          if (ret < 0) {
>              return ret;
>          }
> @@ -282,11 +286,12 @@ int nbd_client_session_co_writev(NbdClientSession 
> *client, int64_t sector_num,
>          sector_num += NBD_MAX_SECTORS;
>          nb_sectors -= NBD_MAX_SECTORS;
>      }
> -    return nbd_co_writev_1(client, sector_num, nb_sectors, qiov, offset);
> +    return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
>  }
>  
> -int nbd_client_session_co_flush(NbdClientSession *client)
> +int nbd_client_session_co_flush(BlockDriverState *bs)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      struct nbd_request request = { .type = NBD_CMD_FLUSH };
>      struct nbd_reply reply;
>      ssize_t ret;
> @@ -303,7 +308,7 @@ int nbd_client_session_co_flush(NbdClientSession *client)
>      request.len = 0;
>  
>      nbd_coroutine_start(client, &request);
> -    ret = nbd_co_send_request(client, &request, NULL, 0);
> +    ret = nbd_co_send_request(bs, &request, NULL, 0);
>      if (ret < 0) {
>          reply.error = -ret;
>      } else {
> @@ -313,9 +318,10 @@ int nbd_client_session_co_flush(NbdClientSession *client)
>      return -reply.error;
>  }
>  
> -int nbd_client_session_co_discard(NbdClientSession *client, int64_t 
> sector_num,
> -    int nb_sectors)
> +int nbd_client_session_co_discard(BlockDriverState *bs, int64_t sector_num,
> +                                  int nb_sectors)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      struct nbd_request request = { .type = NBD_CMD_TRIM };
>      struct nbd_reply reply;
>      ssize_t ret;
> @@ -327,7 +333,7 @@ int nbd_client_session_co_discard(NbdClientSession 
> *client, int64_t sector_num,
>      request.len = nb_sectors * 512;
>  
>      nbd_coroutine_start(client, &request);
> -    ret = nbd_co_send_request(client, &request, NULL, 0);
> +    ret = nbd_co_send_request(bs, &request, NULL, 0);
>      if (ret < 0) {
>          reply.error = -ret;
>      } else {
> @@ -338,43 +344,41 @@ int nbd_client_session_co_discard(NbdClientSession 
> *client, int64_t sector_num,
>  
>  }
>  
> -void nbd_client_session_detach_aio_context(NbdClientSession *client)
> +void nbd_client_session_detach_aio_context(BlockDriverState *bs)
>  {
> -    aio_set_fd_handler(bdrv_get_aio_context(client->bs), client->sock,
> -                       NULL, NULL, NULL);
> +    aio_set_fd_handler(bdrv_get_aio_context(bs),
> +                       nbd_get_client_session(bs)->sock, NULL, NULL, NULL);
>  }
>  
> -void nbd_client_session_attach_aio_context(NbdClientSession *client,
> +void nbd_client_session_attach_aio_context(BlockDriverState *bs,
>                                             AioContext *new_context)
>  {
> -    aio_set_fd_handler(new_context, client->sock,
> -                       nbd_reply_ready, NULL, client);
> +    aio_set_fd_handler(new_context, nbd_get_client_session(bs)->sock,
> +                       nbd_reply_ready, NULL, bs);
>  }
>  
> -void nbd_client_session_close(NbdClientSession *client)
> +void nbd_client_session_close(BlockDriverState *bs)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      struct nbd_request request = {
>          .type = NBD_CMD_DISC,
>          .from = 0,
>          .len = 0
>      };
>  
> -    if (!client->bs) {
> -        return;
> -    }
>      if (client->sock == -1) {
>          return;
>      }
>  
>      nbd_send_request(client->sock, &request);
>  
> -    nbd_teardown_connection(client);
> -    client->bs = NULL;
> +    nbd_teardown_connection(bs);
>  }
>  
> -int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
> +int nbd_client_session_init(BlockDriverState *bs,
>                              int sock, const char *export, Error **errp)
>  {
> +    NbdClientSession *client = nbd_get_client_session(bs);
>      int ret;
>  
>      /* NBD handshake */
> @@ -391,13 +395,12 @@ int nbd_client_session_init(NbdClientSession *client, 
> BlockDriverState *bs,
>  
>      qemu_co_mutex_init(&client->send_mutex);
>      qemu_co_mutex_init(&client->free_sema);
> -    client->bs = bs;
>      client->sock = sock;
>  
>      /* Now that we're connected, set the socket to be non-blocking and
>       * kick the reply mechanism.  */
>      qemu_set_nonblock(sock);
> -    nbd_client_session_attach_aio_context(client, bdrv_get_aio_context(bs));
> +    nbd_client_session_attach_aio_context(bs, bdrv_get_aio_context(bs));
>  
>      logout("Established connection with NBD server\n");
>      return 0;
> diff --git a/block/nbd-client.h b/block/nbd-client.h
> index cfeecc2..49daccc 100644
> --- a/block/nbd-client.h
> +++ b/block/nbd-client.h
> @@ -31,24 +31,24 @@ typedef struct NbdClientSession {
>      struct nbd_reply reply;
>  
>      bool is_unix;
> -
> -    BlockDriverState *bs;
>  } NbdClientSession;
>  
> -int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
> +NbdClientSession *nbd_get_client_session(BlockDriverState *bs);
> +
> +int nbd_client_session_init(BlockDriverState *bs,
>                              int sock, const char *export_name, Error **errp);
> -void nbd_client_session_close(NbdClientSession *client);
> +void nbd_client_session_close(BlockDriverState *bs);
>  
> -int nbd_client_session_co_discard(NbdClientSession *client, int64_t 
> sector_num,
> +int nbd_client_session_co_discard(BlockDriverState *bs, int64_t sector_num,
>                                    int nb_sectors);
> -int nbd_client_session_co_flush(NbdClientSession *client);
> -int nbd_client_session_co_writev(NbdClientSession *client, int64_t 
> sector_num,
> +int nbd_client_session_co_flush(BlockDriverState *bs);
> +int nbd_client_session_co_writev(BlockDriverState *bs, int64_t sector_num,
>                                   int nb_sectors, QEMUIOVector *qiov);
> -int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
> +int nbd_client_session_co_readv(BlockDriverState *bs, int64_t sector_num,
>                                  int nb_sectors, QEMUIOVector *qiov);
>  
> -void nbd_client_session_detach_aio_context(NbdClientSession *client);
> -void nbd_client_session_attach_aio_context(NbdClientSession *client,
> +void nbd_client_session_detach_aio_context(BlockDriverState *bs);
> +void nbd_client_session_attach_aio_context(BlockDriverState *bs,
>                                             AioContext *new_context);
>  
>  #endif /* NBD_CLIENT_H */
> diff --git a/block/nbd.c b/block/nbd.c
> index 2e20831..f71fba0 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -224,6 +224,12 @@ static void nbd_config(BDRVNBDState *s, QDict *options, 
> char **export,
>      }
>  }
>  
> +NbdClientSession *nbd_get_client_session(BlockDriverState *bs)
> +{
> +    BDRVNBDState *s = bs->opaque;
> +    return &s->client;
> +}
> +
>  static int nbd_establish_connection(BlockDriverState *bs, Error **errp)
>  {
>      BDRVNBDState *s = bs->opaque;
> @@ -271,7 +277,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, 
> int flags,
>      }
>  
>      /* NBD handshake */
> -    result = nbd_client_session_init(&s->client, bs, sock, export, errp);
> +    result = nbd_client_session_init(bs, sock, export, errp);
>      g_free(export);
>      return result;
>  }
> @@ -279,35 +285,24 @@ static int nbd_open(BlockDriverState *bs, QDict 
> *options, int flags,
>  static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
>                          int nb_sectors, QEMUIOVector *qiov)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    return nbd_client_session_co_readv(&s->client, sector_num,
> -                                       nb_sectors, qiov);
> +    return nbd_client_session_co_readv(bs, sector_num, nb_sectors, qiov);
>  }
>  
>  static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
>                           int nb_sectors, QEMUIOVector *qiov)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    return nbd_client_session_co_writev(&s->client, sector_num,
> -                                        nb_sectors, qiov);
> +    return nbd_client_session_co_writev(bs, sector_num, nb_sectors, qiov);
>  }
>  
>  static int nbd_co_flush(BlockDriverState *bs)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    return nbd_client_session_co_flush(&s->client);
> +    return nbd_client_session_co_flush(bs);
>  }
>  
>  static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
>                            int nb_sectors)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    return nbd_client_session_co_discard(&s->client, sector_num,
> -                                         nb_sectors);
> +    return nbd_client_session_co_discard(bs, sector_num, nb_sectors);
>  }
>  
>  static void nbd_close(BlockDriverState *bs)
> @@ -315,7 +310,7 @@ static void nbd_close(BlockDriverState *bs)
>      BDRVNBDState *s = bs->opaque;
>  
>      qemu_opts_del(s->socket_opts);
> -    nbd_client_session_close(&s->client);
> +    nbd_client_session_close(bs);
>  }
>  
>  static int64_t nbd_getlength(BlockDriverState *bs)
> @@ -327,17 +322,13 @@ static int64_t nbd_getlength(BlockDriverState *bs)
>  
>  static void nbd_detach_aio_context(BlockDriverState *bs)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    nbd_client_session_detach_aio_context(&s->client);
> +    nbd_client_session_detach_aio_context(bs);
>  }
>  
>  static void nbd_attach_aio_context(BlockDriverState *bs,
>                                     AioContext *new_context)
>  {
> -    BDRVNBDState *s = bs->opaque;
> -
> -    nbd_client_session_attach_aio_context(&s->client, new_context);
> +    nbd_client_session_attach_aio_context(bs, new_context);
>  }
>  
>  static void nbd_refresh_filename(BlockDriverState *bs)
>