Re: [Qemu-devel] [PATCH 1/2] block: Add bs->node_name to hold the name of a bs node of the bs graph.

[Jeff Cody]

On Thu, Nov 07, 2013 at 04:01:42PM +0100, Benoît Canet wrote:
> Add the minimum of code to prepare the followings patches.
> 
> If no node_name is provided to bdrv_new the bs->node_name is set to 
> "undefined".
> This will allow to have some default string to communicate in QMP and HMP.
> This also make "undefined" a reserved string for bs->node_name.

Hi Benoît,

Is it necessary to have a reserved string, or would an empty
null-terminated string be able to implicitly denote the name as
undefined?

> 
> Signed-off-by: Benoit Canet <address@hidden>
> ---
>  block.c                   | 70 
> +++++++++++++++++++++++++++++++++++------------
>  block/blkverify.c         |  2 +-
>  block/iscsi.c             |  2 +-
>  block/vmdk.c              |  2 +-
>  block/vvfat.c             |  4 +--
>  blockdev.c                |  8 +++---
>  hw/block/xen_disk.c       |  2 +-
>  include/block/block.h     |  3 +-
>  include/block/block_int.h |  9 +++++-
>  qemu-img.c                |  6 ++--
>  qemu-io.c                 |  2 +-
>  qemu-nbd.c                |  2 +-
>  12 files changed, 77 insertions(+), 35 deletions(-)
> 
> diff --git a/block.c b/block.c
> index fd05a80..230e71a 100644
> --- a/block.c
> +++ b/block.c
> @@ -89,6 +89,9 @@ static int coroutine_fn 
> bdrv_co_do_write_zeroes(BlockDriverState *bs,
>  static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
>      QTAILQ_HEAD_INITIALIZER(bdrv_states);
>  
> +static QTAILQ_HEAD(, BlockDriverState) graph_bdrv_states =
> +    QTAILQ_HEAD_INITIALIZER(graph_bdrv_states);
> +
>  static QLIST_HEAD(, BlockDriver) bdrv_drivers =
>      QLIST_HEAD_INITIALIZER(bdrv_drivers);
>  
> @@ -318,14 +321,26 @@ void bdrv_register(BlockDriver *bdrv)
>  }
>  
>  /* create a new block device (by default it is empty) */
> -BlockDriverState *bdrv_new(const char *device_name)
> +BlockDriverState *bdrv_new(const char *device_name, const char *node_name)
>  {
>      BlockDriverState *bs;
>  
>      bs = g_malloc0(sizeof(BlockDriverState));
>      pstrcpy(bs->device_name, sizeof(bs->device_name), device_name);
>      if (device_name[0] != '\0') {
> -        QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
> +        QTAILQ_INSERT_TAIL(&bdrv_states, bs, device_list);
> +    }
> +    /* if node name is given store it in bs and insert bs in the graph bs 
> list
> +     * note: undefined is a reserved node name
> +     */
> +    if (node_name &&
> +        node_name[0] != '\0' &&
> +        strcmp(node_name, "undefined")) {
> +        pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
> +        QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
> +    /* else set the bs node name to undefined for QMP and HMP */
> +    } else {
> +        sprintf(bs->node_name, "undefined");
>      }
>      bdrv_iostatus_disable(bs);
>      notifier_list_init(&bs->close_notifiers);
> @@ -870,7 +885,7 @@ int bdrv_file_open(BlockDriverState **pbs, const char 
> *filename,
>          options = qdict_new();
>      }
>  
> -    bs = bdrv_new("");
> +    bs = bdrv_new("", NULL);
>      bs->options = options;
>      options = qdict_clone_shallow(options);
>  
> @@ -992,7 +1007,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict 
> *options, Error **errp)
>                                         sizeof(backing_filename));
>      }
>  
> -    bs->backing_hd = bdrv_new("");
> +    bs->backing_hd = bdrv_new("", NULL);
>  
>      if (bs->backing_format[0] != '\0') {
>          back_drv = bdrv_find_format(bs->backing_format);
> @@ -1062,7 +1077,7 @@ int bdrv_open(BlockDriverState *bs, const char 
> *filename, QDict *options,
>             instead of opening 'filename' directly */
>  
>          /* if there is a backing file, use it */
> -        bs1 = bdrv_new("");
> +        bs1 = bdrv_new("", NULL);
>          ret = bdrv_open(bs1, filename, NULL, 0, drv, &local_err);
>          if (ret < 0) {
>              bdrv_unref(bs1);
> @@ -1495,7 +1510,7 @@ void bdrv_close_all(void)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          bdrv_close(bs);
>      }
>  }
> @@ -1524,7 +1539,7 @@ static bool bdrv_requests_pending(BlockDriverState *bs)
>  static bool bdrv_requests_pending_all(void)
>  {
>      BlockDriverState *bs;
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          if (bdrv_requests_pending(bs)) {
>              return true;
>          }
> @@ -1554,7 +1569,7 @@ void bdrv_drain_all(void)
>          /* FIXME: We do not have timer support here, so this is effectively
>           * a busy wait.
>           */
> -        QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +        QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>              if (bdrv_start_throttled_reqs(bs)) {
>                  busy = true;
>              }
> @@ -1570,7 +1585,7 @@ void bdrv_drain_all(void)
>  void bdrv_make_anon(BlockDriverState *bs)
>  {
>      if (bs->device_name[0] != '\0') {
> -        QTAILQ_REMOVE(&bdrv_states, bs, list);
> +        QTAILQ_REMOVE(&bdrv_states, bs, device_list);
>      }
>      bs->device_name[0] = '\0';

Do you need to do anything here to remove the BDS from your graph list?
e.g. QTAILQ_REMOVE(&graph_bdrv_states, bs, node_list)

>  }
> @@ -1626,7 +1641,12 @@ static void bdrv_move_feature_fields(BlockDriverState 
> *bs_dest,
>      /* keep the same entry in bdrv_states */
>      pstrcpy(bs_dest->device_name, sizeof(bs_dest->device_name),
>              bs_src->device_name);
> -    bs_dest->list = bs_src->list;
> +    bs_dest->device_list = bs_src->device_list;
> +
> +    /* keep the same entry in graph_bdrv_states */
> +    pstrcpy(bs_dest->node_name, sizeof(bs_dest->node_name),
> +            bs_src->node_name);
> +    bs_dest->node_list   = bs_src->node_list;
>  }
>  
>  /*
> @@ -1950,7 +1970,7 @@ int bdrv_commit_all(void)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          if (bs->drv && bs->backing_hd) {
>              int ret = bdrv_commit(bs);
>              if (ret < 0) {
> @@ -3017,11 +3037,12 @@ void bdrv_iterate_format(void (*it)(void *opaque, 
> const char *name),
>      }
>  }
>  
> +/* This function is to find block backend bs */
>  BlockDriverState *bdrv_find(const char *name)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          if (!strcmp(name, bs->device_name)) {
>              return bs;
>          }
> @@ -3029,19 +3050,32 @@ BlockDriverState *bdrv_find(const char *name)
>      return NULL;
>  }
>  
> +/* This function is to find a node in the bs graph */
> +BlockDriverState *bdrv_find_node(const char *node_name)
> +{
> +    BlockDriverState *bs;
> +
> +    QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
> +        if (!strcmp(node_name, bs->node_name)) {
> +            return bs;
> +        }
> +    }
> +    return NULL;
> +}
> +
>  BlockDriverState *bdrv_next(BlockDriverState *bs)
>  {
>      if (!bs) {
>          return QTAILQ_FIRST(&bdrv_states);
>      }
> -    return QTAILQ_NEXT(bs, list);
> +    return QTAILQ_NEXT(bs, device_list);
>  }
>  
>  void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs), void 
> *opaque)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          it(opaque, bs);
>      }
>  }
> @@ -3061,7 +3095,7 @@ int bdrv_flush_all(void)
>      BlockDriverState *bs;
>      int result = 0;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          int ret = bdrv_flush(bs);
>          if (ret < 0 && !result) {
>              result = ret;
> @@ -4127,7 +4161,7 @@ void bdrv_invalidate_cache_all(void)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          bdrv_invalidate_cache(bs);
>      }
>  }
> @@ -4136,7 +4170,7 @@ void bdrv_clear_incoming_migration_all(void)
>  {
>      BlockDriverState *bs;
>  
> -    QTAILQ_FOREACH(bs, &bdrv_states, list) {
> +    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
>          bs->open_flags = bs->open_flags & ~(BDRV_O_INCOMING);
>      }
>  }
> @@ -4582,7 +4616,7 @@ void bdrv_img_create(const char *filename, const char 
> *fmt,
>              back_flags =
>                  flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
>  
> -            bs = bdrv_new("");
> +            bs = bdrv_new("", NULL);
>  
>              ret = bdrv_open(bs, backing_file->value.s, NULL, back_flags,
>                              backing_drv, &local_err);
> diff --git a/block/blkverify.c b/block/blkverify.c
> index 55819a0..674b6a5 100644
> --- a/block/blkverify.c
> +++ b/block/blkverify.c
> @@ -155,7 +155,7 @@ static int blkverify_open(BlockDriverState *bs, QDict 
> *options, int flags,
>          goto fail;
>      }
>  
> -    s->test_file = bdrv_new("");
> +    s->test_file = bdrv_new("", NULL);
>      ret = bdrv_open(s->test_file, filename, NULL, flags, NULL, &local_err);
>      if (ret < 0) {
>          error_propagate(errp, local_err);
> diff --git a/block/iscsi.c b/block/iscsi.c
> index a2a961e..5031593 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -1461,7 +1461,7 @@ static int iscsi_create(const char *filename, 
> QEMUOptionParameter *options,
>      IscsiLun *iscsilun = NULL;
>      QDict *bs_options;
>  
> -    bs = bdrv_new("");
> +    bs = bdrv_new("", NULL);
>  
>      /* Read out options */
>      while (options && options->name) {
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 32ec8b77..97801c2 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1672,7 +1672,7 @@ static int vmdk_create(const char *filename, 
> QEMUOptionParameter *options,
>          return -ENOTSUP;
>      }
>      if (backing_file) {
> -        BlockDriverState *bs = bdrv_new("");
> +        BlockDriverState *bs = bdrv_new("", NULL);
>          ret = bdrv_open(bs, backing_file, NULL, 0, NULL, errp);
>          if (ret != 0) {
>              bdrv_unref(bs);
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 3ddaa0b..a8b6011 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -2935,7 +2935,7 @@ static int enable_write_target(BDRVVVFATState *s)
>          goto err;
>      }
>  
> -    s->qcow = bdrv_new("");
> +    s->qcow = bdrv_new("", NULL);
>  
>      ret = bdrv_open(s->qcow, s->qcow_filename, NULL,
>              BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH, bdrv_qcow,
> @@ -2951,7 +2951,7 @@ static int enable_write_target(BDRVVVFATState *s)
>      unlink(s->qcow_filename);
>  #endif
>  
> -    s->bs->backing_hd = bdrv_new("");
> +    s->bs->backing_hd = bdrv_new("", NULL);
>      s->bs->backing_hd->drv = &vvfat_write_target;
>      s->bs->backing_hd->opaque = g_malloc(sizeof(void*));
>      *(void**)s->bs->backing_hd->opaque = s;
> diff --git a/blockdev.c b/blockdev.c
> index b260477..ac47413 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -469,7 +469,7 @@ static DriveInfo *blockdev_init(QDict *bs_opts,
>      /* init */
>      dinfo = g_malloc0(sizeof(*dinfo));
>      dinfo->id = g_strdup(qemu_opts_id(opts));
> -    dinfo->bdrv = bdrv_new(dinfo->id);
> +    dinfo->bdrv = bdrv_new(dinfo->id, NULL);
>      dinfo->bdrv->open_flags = snapshot ? BDRV_O_SNAPSHOT : 0;
>      dinfo->bdrv->read_only = ro;
>      dinfo->type = type;
> @@ -1254,7 +1254,7 @@ static void 
> external_snapshot_prepare(BlkTransactionState *common,
>      }
>  
>      /* We will manually add the backing_hd field to the bs later */
> -    state->new_bs = bdrv_new("");
> +    state->new_bs = bdrv_new("", NULL);
>      /* TODO Inherit bs->options or only take explicit options with an
>       * extended QMP command? */
>      ret = bdrv_open(state->new_bs, new_image_file, NULL,
> @@ -1921,7 +1921,7 @@ void qmp_drive_backup(const char *device, const char 
> *target,
>          return;
>      }
>  
> -    target_bs = bdrv_new("");
> +    target_bs = bdrv_new("", NULL);
>      ret = bdrv_open(target_bs, target, NULL, flags, drv, &local_err);
>      if (ret < 0) {
>          bdrv_unref(target_bs);
> @@ -2055,7 +2055,7 @@ void qmp_drive_mirror(const char *device, const char 
> *target,
>      /* Mirroring takes care of copy-on-write using the source's backing
>       * file.
>       */
> -    target_bs = bdrv_new("");
> +    target_bs = bdrv_new("", NULL);
>      ret = bdrv_open(target_bs, target, NULL, flags | BDRV_O_NO_BACKING, drv,
>                      &local_err);
>      if (ret < 0) {
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 098f6c6..d89e025 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -808,7 +808,7 @@ static int blk_connect(struct XenDevice *xendev)
>      if (!blkdev->dinfo) {
>          /* setup via xenbus -> create new block driver instance */
>          xen_be_printf(&blkdev->xendev, 2, "create new bdrv (xenbus 
> setup)\n");
> -        blkdev->bs = bdrv_new(blkdev->dev);
> +        blkdev->bs = bdrv_new(blkdev->dev, NULL);
>          if (blkdev->bs) {
>              Error *local_err = NULL;
>              BlockDriver *drv = 
> bdrv_find_whitelisted_format(blkdev->fileproto,
> diff --git a/include/block/block.h b/include/block/block.h
> index 3560deb..2d27bd9 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -149,7 +149,7 @@ int bdrv_create(BlockDriver *drv, const char* filename,
>      QEMUOptionParameter *options, Error **errp);
>  int bdrv_create_file(const char* filename, QEMUOptionParameter *options,
>                       Error **errp);
> -BlockDriverState *bdrv_new(const char *device_name);
> +BlockDriverState *bdrv_new(const char *device_name, const char *node_name);
>  void bdrv_make_anon(BlockDriverState *bs);
>  void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old);
>  void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top);
> @@ -339,6 +339,7 @@ void bdrv_lock_medium(BlockDriverState *bs, bool locked);
>  void bdrv_eject(BlockDriverState *bs, bool eject_flag);
>  const char *bdrv_get_format_name(BlockDriverState *bs);
>  BlockDriverState *bdrv_find(const char *name);
> +BlockDriverState *bdrv_find_node(const char *node_name);
>  BlockDriverState *bdrv_next(BlockDriverState *bs);
>  void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs),
>                    void *opaque);
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index a48731d..9e44136 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -297,11 +297,18 @@ struct BlockDriverState {
>      BlockdevOnError on_read_error, on_write_error;
>      bool iostatus_enabled;
>      BlockDeviceIoStatus iostatus;
> +
> +    /* the following member give a name to every node on the BlockDriverState
> +     * graph.
> +     */
> +    char node_name[32];
> +    QTAILQ_ENTRY(BlockDriverState) node_list;
> +    /* Device name is the name associated with the "drive" the guest see */
>      char device_name[32];
> +    QTAILQ_ENTRY(BlockDriverState) device_list;
>      HBitmap *dirty_bitmap;
>      int refcnt;
>      int in_use; /* users other than guest access, eg. block migration */
> -    QTAILQ_ENTRY(BlockDriverState) list;
>  
>      QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
>  
> diff --git a/qemu-img.c b/qemu-img.c
> index 926f0a0..215b7b2 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -269,7 +269,7 @@ static BlockDriverState *bdrv_new_open(const char 
> *filename,
>      Error *local_err = NULL;
>      int ret;
>  
> -    bs = bdrv_new("image");
> +    bs = bdrv_new("image", NULL);
>  
>      if (fmt) {
>          drv = bdrv_find_format(fmt);
> @@ -2225,7 +2225,7 @@ static int img_rebase(int argc, char **argv)
>      } else {
>          char backing_name[1024];
>  
> -        bs_old_backing = bdrv_new("old_backing");
> +        bs_old_backing = bdrv_new("old_backing", NULL);
>          bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));
>          ret = bdrv_open(bs_old_backing, backing_name, NULL, BDRV_O_FLAGS,
>                          old_backing_drv, &local_err);
> @@ -2236,7 +2236,7 @@ static int img_rebase(int argc, char **argv)
>              goto out;
>          }
>          if (out_baseimg[0]) {
> -            bs_new_backing = bdrv_new("new_backing");
> +            bs_new_backing = bdrv_new("new_backing", NULL);
>              ret = bdrv_open(bs_new_backing, out_baseimg, NULL, BDRV_O_FLAGS,
>                          new_backing_drv, &local_err);
>              if (ret) {
> diff --git a/qemu-io.c b/qemu-io.c
> index 3b3340a..3e1ea88 100644
> --- a/qemu-io.c
> +++ b/qemu-io.c
> @@ -63,7 +63,7 @@ static int openfile(char *name, int flags, int growable, 
> QDict *opts)
>              return 1;
>          }
>      } else {
> -        qemuio_bs = bdrv_new("hda");
> +        qemuio_bs = bdrv_new("hda", NULL);
>  
>          if (bdrv_open(qemuio_bs, name, opts, flags, NULL, &local_err) < 0) {
>              fprintf(stderr, "%s: can't open device %s: %s\n", progname, name,
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index c26c98e..35ef57c 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -572,7 +572,7 @@ int main(int argc, char **argv)
>          drv = NULL;
>      }
>  
> -    bs = bdrv_new("hda");
> +    bs = bdrv_new("hda", NULL);
>      srcpath = argv[optind];
>      ret = bdrv_open(bs, srcpath, NULL, flags, drv, &local_err);
>      if (ret < 0) {
> -- 
> 1.8.3.2
> 
>