Re: Block: Trouble with kobject initialisation for blk_cmd_filter

[Jens Axboe]

On Tue, Sep 09 2008, FUJITA Tomonori wrote:
> 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).

I agree, under sda/ makes a lot more sense than under sda/queue/

> 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
> guess.

Yeah, it's certainly starting to look like it... The amount of changes
to unbreak it are too large to submit now, so lets postpone it until
2.6.28.

-- 
Jens Axboe

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