Re: [Qemu-devel] [PATCH v4 09/11] block: update return value from bdrv_snapshot_create

[Markus Armbruster]

Pavel Hrdina <address@hidden> writes:

> If we provide error message we don't have to also provide return
> value because we could check if there is any error message or not.
>
> Signed-off-by: Pavel Hrdina <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> ---
>  block.c                   | 24 ++++++++++--------------
>  block/qcow2-snapshot.c    | 12 +++++-------
>  block/qcow2.h             |  6 +++---
>  block/rbd.c               | 15 ++++++---------
>  block/sheepdog.c          |  9 ++++-----
>  include/block/block.h     |  6 +++---
>  include/block/block_int.h |  6 +++---
>  qemu-img.c                |  9 ++++-----
>  savevm.c                  |  4 ++--
>  9 files changed, 40 insertions(+), 51 deletions(-)
>
> diff --git a/block.c b/block.c
> index 17231d2..d009ce7 100644
> --- a/block.c
> +++ b/block.c
> @@ -3304,27 +3304,23 @@ BlockDriverState *bdrv_snapshots(void)
>      return NULL;
>  }
>  
> -int bdrv_snapshot_create(BlockDriverState *bs,
> -                         QEMUSnapshotInfo *sn_info,
> -                         Error **errp)
> +void bdrv_snapshot_create(BlockDriverState *bs,
> +                          QEMUSnapshotInfo *sn_info,
> +                          Error **errp)
>  {
>      BlockDriver *drv = bs->drv;
>  
>      if (!drv) {
>          error_setg(errp, "device '%s' has no medium",
>                     bdrv_get_device_name(bs));
> -        return -ENOMEDIUM;
> -    }
> -    if (drv->bdrv_snapshot_create) {
> -        return drv->bdrv_snapshot_create(bs, sn_info, errp);
> -    }
> -    if (bs->file) {
> -        return bdrv_snapshot_create(bs->file, sn_info, errp);
> +    } else if (drv->bdrv_snapshot_create) {
> +        drv->bdrv_snapshot_create(bs, sn_info, errp);
> +    } else if (bs->file) {
> +        bdrv_snapshot_create(bs->file, sn_info, errp);
> +    } else {
> +        error_setg(errp, "snapshot is not supported for '%s'",
> +                   bdrv_get_format_name(bs));
>      }
> -
> -    error_setg(errp, "snapshot is not supported for '%s'",
> -               bdrv_get_format_name(bs));
> -    return -ENOTSUP;
>  }
>  
>  int bdrv_snapshot_goto(BlockDriverState *bs,
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index b34179e..f49b95f 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -315,9 +315,9 @@ static int find_snapshot_by_id_or_name(BlockDriverState 
> *bs, const char *name)
>  }
>  
>  /* if no id is provided, a new one is constructed */
> -int qcow2_snapshot_create(BlockDriverState *bs,
> -                          QEMUSnapshotInfo *sn_info,
> -                          Error **errp)
> +void qcow2_snapshot_create(BlockDriverState *bs,
> +                           QEMUSnapshotInfo *sn_info,
> +                           Error **errp)
>  {
>      BDRVQcowState *s = bs->opaque;
>      QCowSnapshot *new_snapshot_list = NULL;
> @@ -337,7 +337,7 @@ int qcow2_snapshot_create(BlockDriverState *bs,
>      /* Check that the ID is unique */
>      if (find_snapshot_by_id(bs, sn_info->id_str) >= 0) {
>          error_setg(errp, "parameter 'name' has to be unique ID");
> -        return -EEXIST;
> +        return;
>      }
>  
>      /* Populate sn with passed data */
> @@ -413,14 +413,12 @@ int qcow2_snapshot_create(BlockDriverState *bs,
>        qcow2_check_refcounts(bs, &result, 0);
>      }
>  #endif
> -    return 0;
> +    return;
>  
>  fail:
>      g_free(sn->id_str);
>      g_free(sn->name);
>      g_free(l1_table);
> -
> -    return ret;
>  }

One of the assignment to ret is now redundant: ret = l1_table_offset.

The variable could be eliminated entirely, but that's a matter of taste.
Some people prefer "ret = foo(); if (ret < 0)", others "if (foo() < 0)".

Actually, some of the error_setg()s should perhaps be
error_setg_errno()s.  Then we'd still need ret.

>  
>  /* copy the snapshot 'snapshot_name' into the current disk image */
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 9d93b83..d467478 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -382,9 +382,9 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t 
> offset,
>  int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int 
> nb_sectors);
>  
>  /* qcow2-snapshot.c functions */
> -int qcow2_snapshot_create(BlockDriverState *bs,
> -                          QEMUSnapshotInfo *sn_info,
> -                          Error **errp);
> +void qcow2_snapshot_create(BlockDriverState *bs,
> +                           QEMUSnapshotInfo *sn_info,
> +                           Error **errp);
>  int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
>  int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id);
>  int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab);
> diff --git a/block/rbd.c b/block/rbd.c
> index cdbee18..5167f2c 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -815,16 +815,16 @@ static int qemu_rbd_truncate(BlockDriverState *bs, 
> int64_t offset)
>      return 0;
>  }
>  
> -static int qemu_rbd_snap_create(BlockDriverState *bs,
> -                                QEMUSnapshotInfo *sn_info,
> -                                Error **errp)
> +static void qemu_rbd_snap_create(BlockDriverState *bs,
> +                                 QEMUSnapshotInfo *sn_info,
> +                                 Error **errp)
>  {
>      BDRVRBDState *s = bs->opaque;
>      int r;
>  
>      if (sn_info->name[0] == '\0') {
>          error_setg(errp, "parameter 'name' cannot be empty");
> -        return -EINVAL; /* we need a name for rbd snapshots */
> +        return; /* we need a name for rbd snapshots */
>      }
>  
>      /*
> @@ -834,21 +834,18 @@ static int qemu_rbd_snap_create(BlockDriverState *bs,
>      if (sn_info->id_str[0] != '\0' &&
>          strcmp(sn_info->id_str, sn_info->name) != 0) {
>          error_setg(errp, "ID and name have to be equal");
> -        return -EINVAL;
> +        return;
>      }
>  
>      if (strlen(sn_info->name) >= sizeof(sn_info->id_str)) {
>          error_setg(errp, "parameter 'name' has to be shorter than 127 
> chars");
> -        return -ERANGE;
> +        return;
>      }
>  
>      r = rbd_snap_create(s->image, sn_info->name);
>      if (r < 0) {
>          error_setg_errno(errp, -r, "failed to create snapshot");
> -        return r;
>      }
> -
> -    return 0;
>  }
>  
>  static int qemu_rbd_snap_remove(BlockDriverState *bs,
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index e38bdf5..cf11dfb 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -1767,9 +1767,9 @@ static int coroutine_fn 
> sd_co_flush_to_disk(BlockDriverState *bs)
>      return acb->ret;
>  }
>  
> -static int sd_snapshot_create(BlockDriverState *bs,
> -                              QEMUSnapshotInfo *sn_info,
> -                              Error **errp)
> +static void sd_snapshot_create(BlockDriverState *bs,
> +                               QEMUSnapshotInfo *sn_info,
> +                               Error **errp)
>  {
>      BDRVSheepdogState *s = bs->opaque;
>      int ret, fd;
> @@ -1784,7 +1784,7 @@ static int sd_snapshot_create(BlockDriverState *bs,
>      if (s->is_snapshot) {
>          error_setg(errp, "you can't create a snapshot '%s' of a snapshot VDI 
> "
>                     "%s (%" PRIu32 ")", sn_info->name, s->name, 
> s->inode.vdi_id);
> -        return -EINVAL;
> +        return;
>      }
>  
>      dprintf("%s %s\n", sn_info->name, sn_info->id_str);
> @@ -1836,7 +1836,6 @@ static int sd_snapshot_create(BlockDriverState *bs,
>  
>  cleanup:
>      closesocket(fd);
> -    return ret;
>  }
>  

Same here.

>  static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
> diff --git a/include/block/block.h b/include/block/block.h
> index ee9399c..1a6a6a7 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -331,9 +331,9 @@ BlockStats *bdrv_query_stats(const BlockDriverState *bs);
>  int bdrv_can_snapshot(BlockDriverState *bs);
>  int bdrv_is_snapshot(BlockDriverState *bs);
>  BlockDriverState *bdrv_snapshots(void);
> -int bdrv_snapshot_create(BlockDriverState *bs,
> -                         QEMUSnapshotInfo *sn_info,
> -                         Error **errp);
> +void bdrv_snapshot_create(BlockDriverState *bs,
> +                          QEMUSnapshotInfo *sn_info,
> +                          Error **errp);
>  int bdrv_snapshot_goto(BlockDriverState *bs,
>                         const char *snapshot_id);
>  int bdrv_snapshot_delete(BlockDriverState *bs, const char *snapshot_id);
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 2feaa16..8760517 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -153,9 +153,9 @@ struct BlockDriver {
>      int (*bdrv_write_compressed)(BlockDriverState *bs, int64_t sector_num,
>                                   const uint8_t *buf, int nb_sectors);
>  
> -    int (*bdrv_snapshot_create)(BlockDriverState *bs,
> -                                QEMUSnapshotInfo *sn_info,
> -                                Error **errp);
> +    void (*bdrv_snapshot_create)(BlockDriverState *bs,
> +                                 QEMUSnapshotInfo *sn_info,
> +                                 Error **errp);
>      int (*bdrv_snapshot_goto)(BlockDriverState *bs,
>                                const char *snapshot_id);
>      int (*bdrv_snapshot_delete)(BlockDriverState *bs, const char 
> *snapshot_id);
> diff --git a/qemu-img.c b/qemu-img.c
> index d5f81cc..154d913 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1942,6 +1942,7 @@ static int img_snapshot(int argc, char **argv)
>      int action = 0;
>      qemu_timeval tv;
>      bool quiet = false;
> +    Error *local_err;
>  
>      bdrv_oflags = BDRV_O_FLAGS | BDRV_O_RDWR;
>      /* Parse commandline parameters */
> @@ -2018,11 +2019,9 @@ static int img_snapshot(int argc, char **argv)
>          sn.date_sec = tv.tv_sec;
>          sn.date_nsec = tv.tv_usec * 1000;
>  
> -        ret = bdrv_snapshot_create(bs, &sn, NULL);
> -        if (ret) {
> -            error_report("Could not create snapshot '%s': %d (%s)",
> -                snapshot_name, ret, strerror(-ret));
> -        }
> +        local_err = NULL;
> +        bdrv_snapshot_create(bs, &sn, &local_err);
> +        ret = qemu_img_handle_error(local_err);
>          break;
>  
>      case SNAPSHOT_APPLY:

Error message changes, hopefully for the better.  Should be mentioned in
commit message.

> diff --git a/savevm.c b/savevm.c
> index 7b127eb..6ac4ece 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -2342,8 +2342,8 @@ SnapshotInfo *qmp_vm_snapshot_save(bool has_name, const 
> char *name,
>          if (bdrv_can_snapshot(bs1)) {
>              /* Write VM state size only to the image that contains the state 
> */
>              sn->vm_state_size = (bs == bs1 ? vm_state_size : 0);
> -            ret = bdrv_snapshot_create(bs1, sn, &local_err);
> -            if (ret < 0) {
> +            bdrv_snapshot_create(bs1, sn, &local_err);
> +            if (error_is_set(&local_err)) {
>                  error_propagate(errp, local_err);
>              }
>          }

I think this changes HMP error messages and QMP error objects, hopefully
for the better.  Should be mentioned in commit message.