Re: [Qemu-devel] [PATCH] ide: Add resize callback to ide/core

[Fam Zheng <famz@redhat.com>]

On Tue, 08/12 14:44, John Snow wrote:
> Currently, if the block device backing the IDE drive is resized,
> the information about the device as cached inside of the IDEState
> structure is not updated, thus when a guest OS re-queries the drive,
> it is unable to see the expanded size.
> 
> This patch adds a resize callback to correct this, and marks the
> identify buffer cache as being dirty to force ide_identify to
> regenerate this information. This callback also attempts to update
> the legacy CHS values, if only to maintain a sense of
> informational consistency.
> 
> Lastly, a Linux guest as-is cannot resize a libata drive while in-use,
> but it can see the expanded size as part of a bus rescan event.
> This patch also allows guests such as Linux to see the new drive size
> after a soft reboot event, without having to exit the QEMU process.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  hw/ide/core.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index db191a6..6c86e21 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -2099,6 +2099,30 @@ static bool ide_cd_is_medium_locked(void *opaque)
>      return ((IDEState *)opaque)->tray_locked;
>  }
>  
> +static void ide_resize_cb(void *opaque)
> +{
> +    IDEState *s = opaque;
> +    IDEDevice *dev = s->unit ? s->bus->slave : s->bus->master;
> +    uint64_t nb_sectors;
> +
> +    /* Convince blkconf_geometry to re-determine geometry */
> +    dev->conf.cyls = 0;
> +    dev->conf.heads = 0;
> +    dev->conf.secs = 0;
> +
> +    blkconf_geometry(&dev->conf, &dev->chs_trans, 65536, 16, 255);

blkconf_geometry could return -1 for invalid CHS values that but shouldn't
hurt as far as I can see:

Reviewed-by: Fam Zheng <famz@redhat.com>

> +    bdrv_get_geometry(s->bs, &nb_sectors);
> +
> +    s->nb_sectors = nb_sectors;
> +    s->cylinders = dev->conf.cyls;
> +    s->heads = dev->conf.heads;
> +    s->sectors = dev->conf.secs;
> +    s->chs_trans = dev->chs_trans;
> +
> +    /* Let ide_identify() know it needs to regenerate the response. */
> +    s->identify_set = 0;
> +}
> +
>  static const BlockDevOps ide_cd_block_ops = {
>      .change_media_cb = ide_cd_change_cb,
>      .eject_request_cb = ide_cd_eject_request_cb,
> @@ -2106,6 +2130,10 @@ static const BlockDevOps ide_cd_block_ops = {
>      .is_medium_locked = ide_cd_is_medium_locked,
>  };
>  
> +static const BlockDevOps ide_hd_block_ops = {
> +    .resize_cb = ide_resize_cb,
> +};
> +
>  int ide_init_drive(IDEState *s, BlockDriverState *bs, IDEDriveKind kind,
>                     const char *version, const char *serial, const char *model,
>                     uint64_t wwn,
> @@ -2142,6 +2170,7 @@ int ide_init_drive(IDEState *s, BlockDriverState *bs, IDEDriveKind kind,
>              error_report("Can't use a read-only drive");
>              return -1;
>          }
> +        bdrv_set_dev_ops(bs, &ide_hd_block_ops, s);
>      }
>      if (serial) {
>          pstrcpy(s->drive_serial_str, sizeof(s->drive_serial_str), serial);
> -- 
> 1.9.3
> 
>