Hi,I have a linux *mapper device on the host, I would like to get the start offset.I get this by the following ioctl . Although the call succeeds but it sets the hd_geometry_rec to "0"

I checked through gdb , the ioctl call suceeds ,but sets all the field of hd_geometry to "0"
(gdb) p hd_geometry_rec$2 = {heads = 0 '', sectors = 0 '', cylinders = 0, start = 0}

The device configuration===================[root@localh trunk]# uname -aLinux localh 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

[root@localh trunk]# fdisk -l /dev/mapper/mpath4
Disk /dev/mapper/mpath4: 523 MB, 523960320 bytes255 heads, 63 sectors/track, 63 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes

** * * * * * *Device Boot * * *Start * * * * End * * *Blocks * Id *System/dev/mapper/mpath4p1 * * * * * * * 1 * * * * *10 * * * 80293+ *83 *Linux/dev/mapper/mpath4p2 * * * * * * *11 * * * * *20 * * * 80325 * 83 *Linux
/dev/mapper/mpath4p3 * * * * * * *21 * * * * *30 * * * 80325 * 83 *Linux/dev/mapper/mpath4p4 * * * * * * *31 * * * * *38 * * * 64260 * 83 *Linux[root@localh trunk]#

The Source code============** struct hd_geometry * hd_geometry_rec;** unsigned int*offset;
**// *Here p_ppdevname is */dev/mapper/mpath4p4**if ((fd = open(p_ppdevname, O_RDONLY | O_NONBLOCK)) < 0)
** *{** * *//Error** *}

***
** * * * if ((sts = ioctl(fd, HDIO_GETGEO, &hd_geometry_rec)) < 0)** * * * * {

** * * * * *// Error** * * * * }*** * * *else** * * * * {** * * * * * * offset = (unsigned int) hd_geometry_rec.start;** * * * * }*

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With best regards,
Santosh.


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On 10/14/2010 11:40 AM, Santosh Sarangi wrote:
> Hi,
> I have a linux mapper device on the host, I would like to get the start
> offset.
> I get this by the following ioctl . Although the call succeeds but it sets
> the hd_geometry_rec to "0"
>
> I checked through gdb , the ioctl call suceeds ,but sets all the field of
> hd_geometry to "0"
>
Yep. Device-mapper device are able to report the geometry, but you
have to set it first :-)

The attached patch should fix this.

Cheers,

Hannes
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Dr. Hannes Reinecke zSeries & Storage
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On mar., 2010-11-30 at 08:33 +0100, Hannes Reinecke wrote:
> On 10/14/2010 11:40 AM, Santosh Sarangi wrote:
> > Hi,
> > I have a linux mapper device on the host, I would like to get the start
> > offset.
> > I get this by the following ioctl . Although the call succeeds but it sets
> > the hd_geometry_rec to "0"
> >
> > I checked through gdb , the ioctl call suceeds ,but sets all the field of
> > hd_geometry to "0"
> >
> Yep. Device-mapper device are able to report the geometry, but you
> have to set it first :-)
>
> The attached patch should fix this.
>
Applied.
Thanks.

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