Re: [PATCH 2/4 v2] brd: Add getgeo to block ops
[Posted August 13, 2014 by corbet]
| From: |
| One Thousand Gnomes <gnomes-AT-lxorguk.ukuu.org.uk> |
| To: |
| Boaz Harrosh <boaz-AT-plexistor.com> |
| Subject: |
| Re: [PATCH 2/4 v2] brd: Add getgeo to block ops |
| Date: |
| Thu, 7 Aug 2014 19:20:32 +0100 |
| Message-ID: |
| <20140807192032.70e71fa7@alan.etchedpixels.co.uk> |
| Cc: |
| Jens Axboe <axboe-AT-kernel.dk>, Ross Zwisler <ross.zwisler-AT-linux.intel.com>, Matthew Wilcox <willy-AT-linux.intel.com>, linux-kernel <linux-kernel-AT-vger.kernel.org>, linux-fsdevel <linux-fsdevel-AT-vger.kernel.org> |
| Archive‑link: | |
Article |
On Thu, 07 Aug 2014 17:03:08 +0300
Boaz Harrosh <boaz@plexistor.com> wrote:
> From: Boaz Harrosh <boaz@plexistor.com>
>
> Some programs like fdisk, require HDIO_GETGEO to work, which requires we
> implement getgeo.
>
> We set all hd_geometry members to 1, because this way fdisk
> math will not try its crazy geometry math and get stuff totally wrong.
If you are running a new storage system for god sake don't use DOS
partitioning, use GPT or something sane.
> +static int brd_getgeo(struct block_device *bd, struct hd_geometry *geo)
> +{
> + /* Just tell fdisk to get out of the way. The math here is so
> + * convoluted and does not make any sense at all. With all 1s
> + * The math just gets out of the way.
> + * NOTE: I was trying to get some values that will make fdisk
> + * Want to align first sector on 4K (like 8, 16, 20, ... sectors) but
> + * nothing worked, I searched the net the math is not your regular
> + * simple multiplication at all. If you managed to get these please
> + * fix here. For now we use 4k physical sectors for this
> + */
> + geo->heads = 1;
> + geo->sectors = 1;
> + geo->cylinders = 1;
> + return 0;
This is then going to blow up on your with some other tool. Fix fdisk
instead. Lying to apps generally ends up like children lying to parents -
the lie gets more complicated to keep up each case you find until it
breaks.
Alan
