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

[Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>]

On 12/10/2014 04:14 PM, Thomas Huth wrote:
> 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
>
>

No I don't :) Because raw_probe_blocksizes indeed calls 
bdrv_probe_blocksizes() dispatcher, but it calls it against different
driver: "bs->file". This child points to other driver, which represents
the actual nature of the device.

So the 2nd drv->bdrv_probe_blocksizes() call will actually be
a call to either hdev_probe_blocksizes() for "host_device" driver or
will be null for other drivers.

Kate.