Re: [Qemu-devel] [PATCH v3 3/5] block: Add driver methods to probe blocksizes and geometry

[Thomas Huth <thuth@linux.vnet.ibm.com>]

On Fri,  5 Dec 2014 18:56:19 +0100
Ekaterina Tumanova <tumanova@linux.vnet.ibm.com> wrote:

> This patch introduces driver methods of defining disk blocksizes
> (physical and logical) and hard drive geometry.
> The method is only implemented for "host_device". For "raw" devices
> driver calls child's method.
> 
> For the time being geometry detection will only work for DASD devices.
> In order to check that a local check_for_dasd function was introduced,
> which calls BIODASDINFO2 ioctl and returns its rc.
> 
> Blocksizes detection fuction will probe sizes for DASD devices and
> set default for other devices.
> 
> Signed-off-by: Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>
> ---
>  block/raw-posix.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  block/raw_bsd.c   | 14 +++++++++
>  2 files changed, 105 insertions(+)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 633d5bc..33f9983 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -56,6 +56,7 @@
>  #include <linux/cdrom.h>
>  #include <linux/fd.h>
>  #include <linux/fs.h>
> +#include <linux/hdreg.h>
>  #ifndef FS_NOCOW_FL
>  #define FS_NOCOW_FL                     0x00800000 /* Do not cow file */
>  #endif
> @@ -90,6 +91,10 @@
>  #include <xfs/xfs.h>
>  #endif
> 
> +#ifdef __s390__
> +#include <asm/dasd.h>
> +#endif
> +
>  //#define DEBUG_FLOPPY
> 
>  //#define DEBUG_BLOCK
> @@ -242,6 +247,20 @@ static int probe_logical_blocksize(int fd, unsigned int *sector_size)
>      return 0;
>  }
> 
> +/*
> + * Set physical block size via ioctl. On success return 0. Otherwise -errno.
> + */
> +static int probe_physical_blocksize(int fd, unsigned int *blk_size)
> +{
> +#ifdef BLKPBSZGET
> +    if (ioctl(fd, BLKPBSZGET, blk_size) < 0) {
> +        return -errno;
> +    }
> +#endif
> +
> +    return 0;
> +}
> +
>  static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
>  {
>      BDRVRawState *s = bs->opaque;
> @@ -662,6 +681,76 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>      bs->bl.opt_mem_alignment = s->buf_align;
>  }
> 
> +static int check_for_dasd(int fd)
> +{
> +#ifdef BIODASDINFO2
> +    struct dasd_information2_t info = {0};
> +
> +    return ioctl(fd, BIODASDINFO2, &info);
> +#endif
> +    return -1;

I'd put the "return -1" line into an #else branch of the #ifdef, so
that you do not end up with two consecutive return statements in case
BIODASDINFO2 is defined.

> +}
> +
> +/*
> + * Try to get the device blocksize. On success 0. On failure return -errno.
> + * Currently only implemented for DASD drives.
> + */
> +static int hdev_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
> +{
> +    BDRVRawState *s = bs->opaque;
> +    int ret;
> +
> +    /* If DASD, get blocksizes */
> +    if (check_for_dasd(s->fd) < 0) {
> +        return -1;
> +    }
> +    ret = probe_logical_blocksize(s->fd, &bsz->log);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +    return probe_physical_blocksize(s->fd, &bsz->phys);
> +}
> +
> +/*
> + * Try to get the device geometry. On success 0. On failure return -errno.

"On success return 0"

> + * Currently only implemented for DASD drives.
> + */
> +static int hdev_probe_geometry(BlockDriverState *bs, hdGeometry *geo)
> +{
> +    BDRVRawState *s = bs->opaque;
> +    struct hd_geometry ioctl_geo = {0};
> +    uint32_t blksize;
> +
> +    /* If DASD, get it's geometry */
> +    if (check_for_dasd(s->fd) < 0) {
> +        return -1;
> +    }
> +    if (ioctl(s->fd, HDIO_GETGEO, &ioctl_geo) < 0) {
> +        return -errno;
> +    }
> +    /* HDIO_GETGEO may return success even though geo contains zeros
> +       (e.g. certain multipath setups) */
> +    if (!ioctl_geo.heads || !ioctl_geo.sectors || !ioctl_geo.cylinders) {
> +        return -1;
> +    }
> +    /* Do not return a geometry for partition */
> +    if (ioctl_geo.start != 0) {
> +        return -1;
> +    }
> +    geo->heads = ioctl_geo.heads;
> +    geo->sectors = ioctl_geo.sectors;
> +    if (bs->total_sectors) {

Maybe add a comment here why you've got to calculate the cylinders here
instead of using ioctl_geo.cylinders ?

> +        if (!probe_physical_blocksize(s->fd, &blksize)) {
> +            geo->cylinders = bs->total_sectors / (blksize / BDRV_SECTOR_SIZE)
> +                                               / (geo->heads * geo->sectors);
> +            return 0;
> +        }
> +    }
> +    geo->cylinders = ioctl_geo.cylinders;
> +
> +    return 0;
> +}
> +
>  static ssize_t handle_aiocb_ioctl(RawPosixAIOData *aiocb)
>  {
>      int ret;
> @@ -2127,6 +2216,8 @@ static BlockDriver bdrv_host_device = {
>      .bdrv_get_info = raw_get_info,
>      .bdrv_get_allocated_file_size
>                          = raw_get_allocated_file_size,
> +    .bdrv_probe_blocksizes = hdev_probe_blocksizes,
> +    .bdrv_probe_geometry = hdev_probe_geometry,
> 
>      .bdrv_detach_aio_context = raw_detach_aio_context,
>      .bdrv_attach_aio_context = raw_attach_aio_context,
> diff --git a/block/raw_bsd.c b/block/raw_bsd.c
> index 401b967..cfd5249 100644
> --- a/block/raw_bsd.c
> +++ b/block/raw_bsd.c
> @@ -173,6 +173,18 @@ static int raw_probe(const uint8_t *buf, int buf_size, const char *filename)
>      return 1;
>  }
> 
> +static int raw_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
> +{
> +    bdrv_probe_blocksizes(bs->file, bsz);
> +
> +    return 0;
> +}
> +
> +static int raw_probe_geometry(BlockDriverState *bs, hdGeometry *geo)
> +{
> +    return bdrv_probe_geometry(bs->file, geo);
> +}
> +
>  static BlockDriver bdrv_raw = {
>      .format_name          = "raw",
>      .bdrv_probe           = &raw_probe,
> @@ -190,6 +202,8 @@ static BlockDriver bdrv_raw = {
>      .has_variable_length  = true,
>      .bdrv_get_info        = &raw_get_info,
>      .bdrv_refresh_limits  = &raw_refresh_limits,
> +    .bdrv_probe_blocksizes = &raw_probe_blocksizes,
> +    .bdrv_probe_geometry  = &raw_probe_geometry,
>      .bdrv_is_inserted     = &raw_is_inserted,
>      .bdrv_media_changed   = &raw_media_changed,
>      .bdrv_eject           = &raw_eject,

Hmmm, raw_probe_blocksizes() calls bdrv_probe_blocksizes(), but when I
look at your patch 1/5, bdrv_probe_blocksizes() wants to call
drv->bdrv_probe_blocksizes() (i.e. raw_probe_blocksizes()) again?
Don't you get an endless recursive loop here? Or did I miss something?
*confused*

 Thomas