Re: Block: Trouble with kobject initialisation for blk_cmd_filter

From: FUJITA Tomonori
Date: Tue Sep 09 2008 - 08:46:17 EST

On Tue, 9 Sep 2008 12:28:45 +0200
Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:

> On Fri, Sep 05 2008, Elias Oltmanns wrote:
> > Hi all,
> >
> > current usage of the kobject in struct blk_cmd_filter is flawed. Doing
> > # modprobe -r sd-mod && modprobe sd-mod
> > while, for instance, a usb-stick is plugged in currently results in
> > nasty warnings and a dump_stack(). Since blk_cmd_filter is embedded in
> > struct request_queue, I don't see the need for a kobject anyway. What
> > about the much simpler option of a struct attribute_group in this
> > particular case?
> >
> > This would imply that the cmd_filter subdirectory would appear under
> > sda/queue/ rather than sda/ (which is probably the right place) but,
> > alas, we have to keep compatibility in mind. So I've made some changes
> > to sysfs along the way in order to provide a legacy symlink. I'd have to
> > seperate these two changes for submission but I wanted to know your
> > opinion about it all first.
> >
> > Thinking about it now makes me wonder whether this is too much for a rc
> > patch and whether we should just allocate the struct blk_cmd_filter
> > dynamically and have done with it. Anyway, tell me what you think.
> I think this patch is a step in the right direction, lets get rid of
> that pesky kobject just for the cmdfilter. Can you resend the patch
> _without_ the sysfs changes and link support? We haven't released a
> kernel with cmd filter support yet, so we can change the location still
> and not have to worry about compatability.

The sysfs changes looks too much for 2.6.27-rcX but without the sysfs
changes, we have the cmdfilter under /sys/block/sda/queue/, right? We
don't need to worry about compatibility, but /sys/block/sda is more
appropriate? (though I don't think that the cmd filter is a good idea
so I don't care much).

Jens, would it be better to just disable the cmdfilter stuff for
2.6.27? It's too late for another try to fix this broken stuff, I
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