linux-kernel - Re: UBI fastmap updates

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Message-ID: <4FEEDAA4.30105@nod.at>
Date:	Sat, 30 Jun 2012 12:53:24 +0200
From:	Richard Weinberger <richard@....at>
To:	Artem Bityutskiy <dedekind1@...il.com>
CC:	linux-mtd@...ts.infradead.org, nyoushchenko@...sta.com,
	artem.bityutskiy@...ux.intel.com, linux-kernel@...r.kernel.org,
	adrian.hunter@...el.com, Heinz.Egger@...utronix.de,
	thomas.wucher@...utronix.de, shmulik.ladkani@...il.com,
	tglx@...utronix.de, Marius.Mazarel@...l.ro, tim.bird@...sony.com
Subject: Re: UBI fastmap updates

Am 30.06.2012 12:43, schrieb Artem Bityutskiy:
> On Fri, 2012-06-29 at 17:14 +0200, Richard Weinberger wrote:
>> This is the next round of UBI fastmap updates.
>>
>> Fastmap is now disabled by default.
>> If you attach an image it will not automatically convert it
>> to the fastmap format.
>> UBI has a new module parameter "fm_auto".
>> If set to 1 UBI will create a fastmap automatically on your
>> flash device.
>> Please see commit "Add a module parameter to enable fastmap"
>> for more details.
> 
> One thing I've noticed is that you use vmalloc for some of the buffers
> you do I/O on (fm_raw). This is a problem for many ARM platforms because
> they cannot do DMA on such buffers. The drivers have to implement
> various workarouns for this: either fall back to memcopies or do an
> extra copy to a DMA-able buffers.
> 
> UBI and UBIFS already to I/O on vmalloc'ed buffers, an I am planning to
> fix this, which is not easy. Would be great to not add more of these.

There are only two buffers which use vmalloc() both are used to hold the raw fastmap and have
the same size.
If it helps I could preallocate a buffer in ubi-> and use it in both functions ubi_write_fastmap()
and ubi_scan_fastmap().

So basically you want me to get rid of any vmalloc()'ed buffer?
That's not easy.

Thanks,
//richard


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