Re: [Qemu-devel] [PATCH] iscsi: add iscsi_truncate support

[Paolo Bonzini]

Il 15/02/2013 11:58, Peter Lieven ha scritto:
> this patch adds iscsi_truncate which effectively allows for online
> resizing of iscsi volumes. for this to work you have to resize
> the volume on your storage and then call block_resize command
> in qemu which will issue a readcapacity16 to update the capacity.
> 
> Signed-off-by: Peter Lieven <address@hidden>
> ---
>  block/iscsi.c |   74
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
> 
> diff --git a/block/iscsi.c b/block/iscsi.c
> index deb3b68..37f12b3 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -67,6 +67,12 @@ typedef struct IscsiAIOCB {
>  #endif
>  } IscsiAIOCB;
> 
> +struct IscsiTask {
> +    IscsiLun *iscsilun;
> +    int status;
> +    int complete;
> +};
> +
>  #define NOP_INTERVAL 5000
>  #define MAX_NOP_FAILURES 3
> 
> @@ -700,6 +706,73 @@ iscsi_getlength(BlockDriverState *bs)
>      return len;
>  }
> 
> +static void
> +iscsi_readcapacity16_cb(struct iscsi_context *iscsi, int status,
> +                        void *command_data, void *opaque)
> +{
> +    struct IscsiTask *itask = opaque;
> +    struct scsi_readcapacity16 *rc16;
> +    struct scsi_task *task = command_data;
> +
> +    if (status != 0) {
> +        error_report("iSCSI: Failed to read capacity of iSCSI lun. %s",
> +                     iscsi_get_error(iscsi));
> +        itask->status   = 1;
> +        itask->complete = 1;
> +        scsi_free_scsi_task(task);
> +        return;
> +    }
> +
> +    rc16 = scsi_datain_unmarshall(task);
> +    if (rc16 == NULL) {
> +        error_report("iSCSI: Failed to unmarshall readcapacity16 data.");
> +        itask->status   = 1;
> +        itask->complete = 1;
> +        scsi_free_scsi_task(task);
> +        return;
> +    }
> +
> +    itask->iscsilun->block_size = rc16->block_length;
> +    itask->iscsilun->num_blocks = rc16->returned_lba + 1;
> +
> +    itask->status   = 0;
> +    itask->complete = 1;
> +    scsi_free_scsi_task(task);
> +}
> +
> +static int iscsi_truncate(BlockDriverState *bs, int64_t offset)
> +{
> +    IscsiLun *iscsilun = bs->opaque;
> +    struct IscsiTask itask;
> +    struct scsi_task *task = NULL;
> +
> +    if (iscsilun->type != TYPE_DISK) {
> +        return -ENOTSUP;
> +    }
> +
> +    itask.iscsilun = iscsilun;
> +    itask.status = 0;
> +    itask.complete = 0;
> +
> +    task = iscsi_readcapacity16_task(iscsilun->iscsi, iscsilun->lun,
> +                                 iscsi_readcapacity16_cb, &itask);

You can use iscsi_readcapacity16_sync.  In fact, you probably should
extract code from iscsi_open and reuse it here.

Paolo

> +    if (task == NULL) {
> +         error_report("iSCSI: failed to send readcapacity16 command.");
> +         return -EINVAL;
> +    }
> +
> +    while (!itask.complete) {
> +        iscsi_set_events(iscsilun);
> +        qemu_aio_wait();
> +    }
> +
> +    if (offset > iscsi_getlength(bs)) {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
>  static int parse_chap(struct iscsi_context *iscsi, const char *target)
>  {
>      QemuOptsList *list;
> @@ -1093,6 +1166,7 @@ static BlockDriver bdrv_iscsi = {
>      .create_options  = iscsi_create_options,
> 
>      .bdrv_getlength  = iscsi_getlength,
> +    .bdrv_truncate   = iscsi_truncate,
> 
>      .bdrv_aio_readv  = iscsi_aio_readv,
>      .bdrv_aio_writev = iscsi_aio_writev,