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

[Peter Lieven]

On 15.02.2013 12:09, Paolo Bonzini wrote:
> 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.

Thats not possible afaik. Mixing sync and async commands in libiscsi is
a very bad thing. It will leed to nested event loops.

Peter


> 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,