Re: Few problems in mtd system

[Maxim Levitsky <maximlevitsky@gmail.com>]

On Tue, 2009-12-22 at 21:32 +0100, Michael Trimarchi wrote: 
> Maxim Levitsky wrote:
> > On Mon, 2009-12-21 at 15:00 +0100, Jörn Engel wrote: 
> >   
> >> On Sun, 20 December 2009 22:59:55 +0200, Maxim Levitsky wrote:
> >>     
> >>> I suspect that older non type M cards didn't have such emulation, but
> >>> were real nand chips, bacause there are some references on the web about
> >>> using XD card as a nand chip replacement.
> >>> Such card as I have will really will make very poor nand replacement...
> >>>       
> >> If you want to know whether the cards or the readers are to blame, you
> >> can try to buy an old alauda reader on ebay.  It is too slow to be
> >> useful for most purposes, but I believe it did give me full access with
> >> my cards.
> >>
> >>     
> >>> Folks, could you review my other questions about bugs in mtd core, and
> >>> tell your opinion?
> >>>       
> >
> > I have several problems, more correctly bugs in mtd system I have to fix
> > to make my driver work.
> >
> > Lets start from  the problem I face now.
> >
> > Problem is that add_mtd_blktrans_dev is called with mtd_table_mutex
> > locked, but it calls add_disk which opens the block device if you
> > specify that you need partitions on the disk. Open routine 'looks' at
> > mtd table using get_mtd_device, and thus deadlocks.
> >
> > Do you have a clue how to fix that so it won't break anything?
> >   
> I try to follow the call, can you send the block stack trace?
> just change the lock on get_mtd_device with a try_lock and BUG on
> if it is taken
I don't want to crash the system now, but I know exactly the trace:
(this is created manually)

get_mtd_device
blktrans_open
__blkdev_get
blkdev_get
register_disk
add_disk
add_mtd_blktrans_dev
ssfdcr_add_mtd
blktrans_notify_add
add_mtd_device - takes the lock
rsc_register_nand_device - my driver function


The point is that that ssfdc specifies:

.part_bits = SSFDCR_PARTN_BITS

This triggers the open of the block device by block core.

Tomorrow I will post full backtrace.

Best regards,
Maxim Levitsky