[pbs-devel] applied: [PATCH v2 qemu] PVE: handle PBS write callback with big blocks correctly

[Fabian Grünbichler]

On July 22, 2020 3:47 pm, Stefan Reiter wrote:
> Under certain conditions QEMU will push more than the given blocksize
> into the callback at once. Handle it like VMA does, by iterating the
> data until all is written.
> 
> The block size is stored per backup device to be used in the callback.
> This avoids relying on PROXMOX_BACKUP_DEFAULT_CHUNK_SIZE, in case it is
> made configurable in the future.
> 
> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> ---
> 
> v2:
> * save chunk size explicitly to avoid depending on
>   PROXMOX_BACKUP_DEFAULT_CHUNK_SIZE
> 
>  pve-backup.c | 30 ++++++++++++++++++++++--------
>  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/pve-backup.c b/pve-backup.c
> index 77eb475563..40d8136f1a 100644
> --- a/pve-backup.c
> +++ b/pve-backup.c
> @@ -67,6 +67,7 @@ opts_init(pvebackup_init);
>  typedef struct PVEBackupDevInfo {
>      BlockDriverState *bs;
>      size_t size;
> +    uint64_t block_size;
>      uint8_t dev_id;
>      bool completed;
>      char targetfile[PATH_MAX];
> @@ -147,17 +148,28 @@ pvebackup_co_dump_pbs_cb(
>          return -1;
>      }
>  
> -    pbs_res = proxmox_backup_co_write_data(backup_state.pbs, di->dev_id, buf, start, size, &local_err);
> -    qemu_co_mutex_unlock(&backup_state.dump_callback_mutex);
> +    uint64_t transferred = 0;
> +    uint64_t reused = 0;
> +    while (transferred < size) {
> +        uint64_t left = size - transferred;
> +        uint64_t to_transfer = left < di->block_size ? left : di->block_size;
>  
> -    if (pbs_res < 0) {
> -        pvebackup_propagate_error(local_err);
> -        return pbs_res;
> -    } else {
> -        size_t reused = (pbs_res == 0) ? size : 0;
> -        pvebackup_add_transfered_bytes(size, !buf ? size : 0, reused);
> +        pbs_res = proxmox_backup_co_write_data(backup_state.pbs, di->dev_id,
> +            buf ? buf + transferred : NULL, start + transferred, to_transfer, &local_err);
> +        transferred += to_transfer;
> +
> +        if (pbs_res < 0) {
> +            pvebackup_propagate_error(local_err);
> +            qemu_co_mutex_unlock(&backup_state.dump_callback_mutex);
> +            return pbs_res;
> +        }
> +
> +        reused += pbs_res == 0 ? to_transfer : 0;
>      }
>  
> +    qemu_co_mutex_unlock(&backup_state.dump_callback_mutex);
> +    pvebackup_add_transfered_bytes(size, !buf ? size : 0, reused);
> +
>      return size;
>  }
>  
> @@ -730,6 +742,8 @@ static void coroutine_fn pvebackup_co_prepare(void *opaque)
>              PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
>              l = g_list_next(l);
>  
> +            di->block_size = dump_cb_block_size;
> +
>              const char *devname = bdrv_get_device_name(di->bs);
>  
>              BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(di->bs, PBS_BITMAP_NAME);
> -- 
> 2.20.1
> 
> 
> 
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