On Friday, 27 August 1999 at 8:55:04 +0200, Poul-Henning Kamp wrote:
> In message <[EMAIL PROTECTED]>, Greg Lehey writes:
>> On Thursday, 26 August 1999 at 16:25:14 -0700, Matthew Dillon wrote:
>>>>>> int devminor; /* minor number */
>>>>>>
>>>>>> devminor = minor(dev);
>>>>>> + dev->si_bsize_phys = DEV_BSIZE;
>>>>>> + dev->si_bsize_best = BLKDEV_IOSIZE;
>>>>>> + dev->si_bsize_max = MAXBSIZE;
>>>>>
>>>>> Bingo! Thank you.
>>>>
>>>> Cool, I expect grog will commit it soon.
>>
>> So did I until I read this message.
>>
>>> The patch for ccd is not quite right. Here is the patch from my
>>> big fat patch at http://www.backplane.com/FreeBSD4/
>>>
>>> The problem is that you cannot simply set the physical sector
>>> size to DEV_BSIZE if the underlying device has a larger sector
>>> size. If you do, specfs's blocksize alignment (another fix in
>>> my big fat patch) will be incorrect and result in an I/O error
>>> on the physical media.
>>>
>>> For example, swap-backed VN devices have a sector size of one page,
>>> i.e. 4K.
>>
>> Vinum currently doesn't track the sector size of the drives. I'll
>> have to put some code in there to DTRT. In the meantime, I'll set
>> si_bsize_best to 4K in the hope that this will be OK. Are there any
>> larger block sizes in current use?
>
> 4K is probably too conservative, it only applies if you have a
> swap-backed vn device at the bottom, which would be a truly
> weird thing to do with vinum.
I think I've heard of people doing things like this. Cybernet were
thinking of it a long time ago, but I think I've talked them out of
it.
> Don't spend too much time on tracking the sector size yet. I think
> the si_bsize stuff needs some thinking before we do more with it.
OK, I'll set it to 4 kB at the moment and make a note to myself to fix
it when dev_t stops changing.
Greg
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