Re: [Qemu-devel] [PATCH V4 1/6] snapshot: add parameter *errp in snapshot create

[Max Reitz]

On 14.10.2013 23:52, Wenchao Xia wrote:
> The return value is only used for error report before this patch,
> so change the function protype to return void.
>
> Signed-off-by: Wenchao Xia <address@hidden>
> ---
>  block/qcow2-snapshot.c    |   27 +++++++++++++++++++++++----
>  block/qcow2.h             |    4 +++-
>  block/rbd.c               |   21 ++++++++++++---------
>  block/sheepdog.c          |   29 ++++++++++++++++++++---------
>  block/snapshot.c          |   19 +++++++++++++------
>  blockdev.c                |   10 ++++------
>  include/block/block_int.h |    5 +++--
>  include/block/snapshot.h  |    5 +++--
>  qemu-img.c                |   10 ++++++----
>  savevm.c                  |   12 ++++++++----
>  10 files changed, 95 insertions(+), 47 deletions(-)
>
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index 3529c68..b373f9a 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -347,7 +347,9 @@ static int find_snapshot_by_id_or_name(BlockDriverState 
> *bs,
>  }
>  
>  /* if no id is provided, a new one is constructed */
> -int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
> +void qcow2_snapshot_create(BlockDriverState *bs,
> +                           QEMUSnapshotInfo *sn_info,
> +                           Error **errp)
>  {
>      BDRVQcowState *s = bs->opaque;
>      QCowSnapshot *new_snapshot_list = NULL;
> @@ -366,7 +368,8 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>  
>      /* Check that the ID is unique */
>      if (find_snapshot_by_id_and_name(bs, sn_info->id_str, NULL) >= 0) {
> -        return -EEXIST;
> +        error_setg(errp, "Snapshot with id %s already exist", 
> sn_info->id_str);
> +        return;
>      }
>  
>      /* Populate sn with passed data */
> @@ -383,6 +386,9 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>      l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * 
> sizeof(uint64_t));
>      if (l1_table_offset < 0) {
>          ret = l1_table_offset;
> +        error_setg(errp,
> +                   "Failed in allocation of snapshot L1 table: %d (%s)",
> +                   ret, strerror(-ret));

You may want to use error_setg_errno instead (here and in many other
places in this patch).

>          goto fail;
>      }
>  
> @@ -397,12 +403,20 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>      ret = qcow2_pre_write_overlap_check(bs, 0, sn->l1_table_offset,
>                                          s->l1_size * sizeof(uint64_t));
>      if (ret < 0) {
> +        error_setg(errp, "Failed in overlap check for snapshot L1 table at %"
> +                   PRIu64 " with size %" PRIu64 ": %d (%s)",
> +                   sn->l1_table_offset, s->l1_size * sizeof(uint64_t),
> +                   ret, strerror(-ret));

s->l1_size * sizeof(uint64_t) is of the same type as uint64_t (PRIu64)
only on 64 bit systems. On 32 bit systems, it probably is the same as
uint32_t (because of a different size_t width).

>          goto fail;
>      }
>  
>      ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
>                        s->l1_size * sizeof(uint64_t));
>      if (ret < 0) {
> +        error_setg(errp, "Failed in update of snapshot L1 table at %"
> +                   PRIu64 " with size %" PRIu64 ": %d (%s)",
> +                   sn->l1_table_offset, s->l1_size * sizeof(uint64_t),
> +                   ret, strerror(-ret));

Same here.

>          goto fail;
>      }
>  
> @@ -416,6 +430,9 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>       */
>      ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 
> 1);
>      if (ret < 0) {
> +        error_setg(errp, "Failed in update of refcount for snapshot at %"
> +                   PRIu64 " with size %d: %d (%s)",
> +                   s->l1_table_offset, s->l1_size,  ret, strerror(-ret));
>          goto fail;
>      }
>  
> @@ -431,6 +448,8 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>  
>      ret = qcow2_write_snapshots(bs);
>      if (ret < 0) {
> +        /* Following line will be replaced with more detailed error later */
> +        error_setg(errp, "Failed in write of snapshot");
>          g_free(s->snapshots);
>          s->snapshots = old_snapshot_list;
>          s->nb_snapshots--;
> @@ -452,14 +471,14 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>        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;
> +    return;
>  }
>  
>  /* copy the snapshot 'snapshot_name' into the current disk image */
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 922e190..c0a3d01 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -481,7 +481,9 @@ int qcow2_zero_clusters(BlockDriverState *bs, uint64_t 
> offset, int nb_sectors);
>  int qcow2_expand_zero_clusters(BlockDriverState *bs);
>  
>  /* qcow2-snapshot.c functions */
> -int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
> +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,
> diff --git a/block/rbd.c b/block/rbd.c
> index 4a1ea5b..6181999 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -860,14 +860,16 @@ static int qemu_rbd_truncate(BlockDriverState *bs, 
> int64_t offset)
>      return 0;
>  }
>  
> -static int qemu_rbd_snap_create(BlockDriverState *bs,
> -                                QEMUSnapshotInfo *sn_info)
> +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') {
> -        return -EINVAL; /* we need a name for rbd snapshots */
> +        error_setg(errp, "rbd snapshot need a valid name");

*needs (or "requires")

> +        return; /* we need a name for rbd snapshots */
>      }
>  
>      /*
> @@ -876,20 +878,21 @@ static int qemu_rbd_snap_create(BlockDriverState *bs,
>       */
>      if (sn_info->id_str[0] != '\0' &&
>          strcmp(sn_info->id_str, sn_info->name) != 0) {
> -        return -EINVAL;
> +        error_setg(errp, "rbd snapshot id should be empty or equal to name");
> +        return;
>      }
>  
>      if (strlen(sn_info->name) >= sizeof(sn_info->id_str)) {
> -        return -ERANGE;
> +        error_setg(errp, "rbd snapshot name is too long");
> +        return;
>      }
>  
>      r = rbd_snap_create(s->image, sn_info->name);
>      if (r < 0) {
> -        error_report("failed to create snap: %s", strerror(-r));
> -        return r;
> +        error_setg(errp,
> +                   "Failed to create snapshot: %d (%s)",
> +                   r, strerror(-r));
>      }
> -
> -    return 0;
>  }
>  
>  static int qemu_rbd_snap_remove(BlockDriverState *bs,
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index 5f81c93..67aaeb7 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -1961,7 +1961,9 @@ static int coroutine_fn 
> sd_co_flush_to_disk(BlockDriverState *bs)
>      return acb->ret;
>  }
>  
> -static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo 
> *sn_info)
> +static void sd_snapshot_create(BlockDriverState *bs,
> +                               QEMUSnapshotInfo *sn_info,
> +                               Error **errp)
>  {
>      BDRVSheepdogState *s = bs->opaque;
>      int ret, fd;
> @@ -1974,10 +1976,10 @@ static int sd_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>              s->name, sn_info->vm_state_size, s->is_snapshot);
>  
>      if (s->is_snapshot) {
> -        error_report("You can't create a snapshot of a snapshot VDI, "
> -                     "%s (%" PRIu32 ").", s->name, s->inode.vdi_id);
> +        error_setg(errp, "You can't create a snapshot of a snapshot VDI, "
> +                   "%s (%" PRIu32 ")", s->name, s->inode.vdi_id);
>  
> -        return -EINVAL;
> +        return;
>      }
>  
>      DPRINTF("%s %s\n", sn_info->name, sn_info->id_str);
> @@ -1995,21 +1997,27 @@ static int sd_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>      fd = connect_to_sdog(s);
>      if (fd < 0) {
>          ret = fd;
> +        error_setg(errp, "Failed to connect: %d (%s)", ret, strerror(-ret));

You may remove the "ret = fd" line before the error_setg(), if you want
to; but then you'd have to replace the ret in the error_setg() by fd (it
should be an error_setg_errno() again, anyway). Do as you please.

>          goto cleanup;
>      }
>  
>      ret = write_object(fd, (char *)&s->inode, 
> vid_to_vdi_oid(s->inode.vdi_id),
>                         s->inode.nr_copies, datalen, 0, false, 
> s->cache_flags);
>      if (ret < 0) {
> -        error_report("failed to write snapshot's inode.");
> +        error_setg(errp,
> +                   "Failed to write snapshot's inode: %d (%s)",
> +                   ret, strerror(-ret));
>          goto cleanup;
>      }
>  
>      ret = do_sd_create(s, s->name, s->inode.vdi_size, s->inode.vdi_id, 
> &new_vid,
>                         1);
>      if (ret < 0) {
> -        error_report("failed to create inode for snapshot. %s",
> -                     strerror(errno));
> +        error_setg(errp,
> +                   "Failed to create inode for snapshot: %d (%s), "
> +                   "errno %d (%s)",
> +                   ret, strerror(-ret),
> +                   errno, strerror(errno));

This and the following hunk are actually places, where error_setg()
seems better than error_setg_errno() (because it's unclear whether -ret
or errno contains the true error value).

Max

>          goto cleanup;
>      }
>  
> @@ -2019,7 +2027,10 @@ static int sd_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>                        s->inode.nr_copies, datalen, 0, s->cache_flags);
>  
>      if (ret < 0) {
> -        error_report("failed to read new inode info. %s", strerror(errno));
> +        error_setg(errp, "Failed to read new inode info: %d (%s), "
> +                   "errno %d (%s)",
> +                   ret, strerror(-ret),
> +                   errno, strerror(errno));
>          goto cleanup;
>      }
>  
> @@ -2029,7 +2040,7 @@ static int sd_snapshot_create(BlockDriverState *bs, 
> QEMUSnapshotInfo *sn_info)
>  
>  cleanup:
>      closesocket(fd);
> -    return ret;
> +    return;
>  }
>  
>  /*
> diff --git a/block/snapshot.c b/block/snapshot.c
> index a05c0c0..3122e3c 100644
> --- a/block/snapshot.c
> +++ b/block/snapshot.c
> @@ -138,20 +138,27 @@ int bdrv_can_snapshot(BlockDriverState *bs)
>      return 1;
>  }
>  
> -int bdrv_snapshot_create(BlockDriverState *bs,
> -                         QEMUSnapshotInfo *sn_info)
> +void bdrv_snapshot_create(BlockDriverState *bs,
> +                          QEMUSnapshotInfo *sn_info,
> +                          Error **errp)
>  {
>      BlockDriver *drv = bs->drv;
>      if (!drv) {
> -        return -ENOMEDIUM;
> +        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
> +        return;
>      }
>      if (drv->bdrv_snapshot_create) {
> -        return drv->bdrv_snapshot_create(bs, sn_info);
> +        drv->bdrv_snapshot_create(bs, sn_info, errp);
> +        return;
>      }
>      if (bs->file) {
> -        return bdrv_snapshot_create(bs->file, sn_info);
> +        bdrv_snapshot_create(bs->file, sn_info, errp);
> +        return;
>      }
> -    return -ENOTSUP;
> +
> +    error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
> +              drv->format_name, bdrv_get_device_name(bs),
> +              "internal snapshot creation");
>  }
>  
>  int bdrv_snapshot_goto(BlockDriverState *bs,
> diff --git a/blockdev.c b/blockdev.c
> index 4f76e28..c4e7124 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1077,7 +1077,7 @@ static void 
> internal_snapshot_prepare(BlkTransactionState *common,
>      qemu_timeval tv;
>      BlockdevSnapshotInternal *internal;
>      InternalSnapshotState *state;
> -    int ret1;
> +    Error *local_err = NULL;
>  
>      g_assert(common->action->kind ==
>               TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC);
> @@ -1135,11 +1135,9 @@ static void 
> internal_snapshot_prepare(BlkTransactionState *common,
>      sn->date_nsec = tv.tv_usec * 1000;
>      sn->vm_clock_nsec = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>  
> -    ret1 = bdrv_snapshot_create(bs, sn);
> -    if (ret1 < 0) {
> -        error_setg_errno(errp, -ret1,
> -                         "Failed to create snapshot '%s' on device '%s'",
> -                         name, device);
> +    bdrv_snapshot_create(bs, sn, &local_err);
> +    if (error_is_set(&local_err)) {
> +        error_propagate(errp, local_err);
>          return;
>      }
>  
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index a48731d..553d843 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -161,8 +161,9 @@ 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);
> +    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,
> diff --git a/include/block/snapshot.h b/include/block/snapshot.h
> index 012bf22..a998316 100644
> --- a/include/block/snapshot.h
> +++ b/include/block/snapshot.h
> @@ -47,8 +47,9 @@ bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
>                                         QEMUSnapshotInfo *sn_info,
>                                         Error **errp);
>  int bdrv_can_snapshot(BlockDriverState *bs);
> -int bdrv_snapshot_create(BlockDriverState *bs,
> -                         QEMUSnapshotInfo *sn_info);
> +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,
> diff --git a/qemu-img.c b/qemu-img.c
> index 926f0a0..aa8b46f 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -2080,10 +2080,12 @@ 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);
> -        if (ret) {
> -            error_report("Could not create snapshot '%s': %d (%s)",
> -                snapshot_name, ret, strerror(-ret));
> +        bdrv_snapshot_create(bs, &sn, &err);
> +        if (error_is_set(&err)) {
> +            error_report("Could not create snapshot '%s': %s",
> +                         snapshot_name, error_get_pretty(err));
> +            error_free(err);
> +            ret = 1;
>          }
>          break;
>  
> diff --git a/savevm.c b/savevm.c
> index 2f631d4..617d6eb 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -2366,6 +2366,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
>      qemu_timeval tv;
>      struct tm tm;
>      const char *name = qdict_get_try_str(qdict, "name");
> +    Error *err = NULL;
>  
>      /* Verify if there is a device that doesn't support snapshots and is 
> writable */
>      bs = NULL;
> @@ -2439,10 +2440,13 @@ void do_savevm(Monitor *mon, const QDict *qdict)
>          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);
> -            if (ret < 0) {
> -                monitor_printf(mon, "Error while creating snapshot on 
> '%s'\n",
> -                               bdrv_get_device_name(bs1));
> +            bdrv_snapshot_create(bs1, sn, &err);
> +            if (error_is_set(&err)) {
> +                monitor_printf(mon,
> +                               "Error while creating snapshot on '%s': %s\n",
> +                               bdrv_get_device_name(bs1),
> +                               error_get_pretty(err));
> +                error_free(err);
>              }
>          }
>      }