* jffs on non-MTD device?
@ 2001-05-24 22:52 Pavel Machek
2001-05-25 8:44 ` David Woodhouse
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Pavel Machek @ 2001-05-24 22:52 UTC (permalink / raw)
To: kernel list, jffs-dev
Hi!
I'm trying to run jffs on my ATA-flash disk (running ext2 could kill
some flash cells too soon, right?) but it refuses:
if (MAJOR(dev) != MTD_BLOCK_MAJOR) {
printk(KERN_WARNING "JFFS: Trying to mount a "
"non-mtd device.\n");
return 0;
}
What are reasons for this check?
Pavel
--
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: jffs on non-MTD device?
2001-05-24 22:52 jffs on non-MTD device? Pavel Machek
@ 2001-05-25 8:44 ` David Woodhouse
2001-06-11 11:45 ` Padraig Brady
2001-06-11 12:41 ` David Woodhouse
2 siblings, 0 replies; 4+ messages in thread
From: David Woodhouse @ 2001-05-25 8:44 UTC (permalink / raw)
To: Pavel Machek; +Cc: kernel list, jffs-dev
pavel@suse.cz said:
> I'm trying to run jffs on my ATA-flash disk (running ext2 could kill
> some flash cells too soon, right?) but it refuses:
CompactFlash does wear levelling internally.
> if (MAJOR(dev) != MTD_BLOCK_MAJOR) {
> printk(KERN_WARNING "JFFS: Trying to mount a "
> "non-mtd device.\n");
> return 0;
> }
> What are reasons for this check?
JFFS doesn't actually use the block device interface. Specifying it in the
mount command is simply a hack to make life easier, which nobody's yet
managed to obsolete. We actually use the underlying MTD device:
mtd = get_mtd_device(NULL, MINOR(dev));
If you want JFFS (or JFFS2) on a CF device - in the apparent absence of any
other relatively low overhead, compressing, journalling file system to use
on it - then you need to provide a translation driver similar to the mtdram
one which fakes an MTD device, using a block device as backing store.
--
dwmw2
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: jffs on non-MTD device?
2001-05-24 22:52 jffs on non-MTD device? Pavel Machek
2001-05-25 8:44 ` David Woodhouse
@ 2001-06-11 11:45 ` Padraig Brady
2001-06-11 12:41 ` David Woodhouse
2 siblings, 0 replies; 4+ messages in thread
From: Padraig Brady @ 2001-06-11 11:45 UTC (permalink / raw)
To: Pavel Machek; +Cc: kernel list, jffs-dev
Some (most?) CF disks have hareware wareleveling.
I use ext2 with e2compr patch.
Padraig.
Pavel Machek wrote:
>Hi!
>
>I'm trying to run jffs on my ATA-flash disk (running ext2 could kill
>some flash cells too soon, right?) but it refuses:
>
> if (MAJOR(dev) != MTD_BLOCK_MAJOR) {
> printk(KERN_WARNING "JFFS: Trying to mount a "
> "non-mtd device.\n");
> return 0;
> }
>
>What are reasons for this check?
>
> Pavel
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: jffs on non-MTD device?
2001-05-24 22:52 jffs on non-MTD device? Pavel Machek
2001-05-25 8:44 ` David Woodhouse
2001-06-11 11:45 ` Padraig Brady
@ 2001-06-11 12:41 ` David Woodhouse
2 siblings, 0 replies; 4+ messages in thread
From: David Woodhouse @ 2001-06-11 12:41 UTC (permalink / raw)
To: Padraig Brady; +Cc: Pavel Machek, kernel list, jffs-dev
Padraig@AnteFacto.com said:
> Some (most?) CF disks have hareware wareleveling. I use ext2 with
> e2compr patch.
There are some who want a journalling filesystem on their CF device.
Did anyone do e3compr yet? :)
Personally, I wouldn't bother with it - these things have a form of
pseudo-filesystem, probably similar to FTL or NFTL, implemented internally
to emulate a block device, and it's been reported that they don't do that
particularly well - they break down and lose data if you put them through
the kind of repeated power cycle tests that JFFS and JFFS2 have been
subjected to. A journalling filesystem on an unreliable medium is sort of
pointless.
Far better to use a real flash device. But maybe I'm biased :)
--
dwmw2
^ permalink raw reply [flat|nested] 4+ messages in thread
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2001-05-24 22:52 jffs on non-MTD device? Pavel Machek
2001-05-25 8:44 ` David Woodhouse
2001-06-11 11:45 ` Padraig Brady
2001-06-11 12:41 ` David Woodhouse
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