Re: MTD/block regression (was Re: Slub debugging NAND error in 2.6.25.10.atmel.2)

[Jens Axboe <jens.axboe@oracle.com>]

On Sun, Aug 31 2008, Geert Uytterhoeven wrote:
> On Sat, 30 Aug 2008, FUJITA Tomonori wrote:
> > On Fri, 29 Aug 2008 16:28:24 +0200
> > Haavard Skinnemoen <haavard.skinnemoen@atmel.com> wrote:
> > > Haavard Skinnemoen <haavard.skinnemoen@atmel.com> wrote:
> > > > Hmm...I just saw this when booting 2.6.27-rc5 on the NGW100:
> > > > 
> > > > kobject (91ce8410): tried to init an initialized object, something is seriously wrong.
> > > > Call trace:
> > > >  [<90017184>] dump_stack+0x18/0x20
> > > >  [<900c1894>] kobject_init+0x28/0x5c
> > > >  [<900c1bf6>] kobject_init_and_add+0xe/0x24
> > > >  [<900beff0>] blk_register_filter+0x28/0x40
> > > >  [<900be224>] add_disk+0x38/0x68
> > > >  [<900e70f0>] add_mtd_blktrans_dev+0x174/0x184
> > > >  [<900e748e>] mtdblock_add_mtd+0x36/0x3c
> > > >  [<900e6e38>] blktrans_notify_add+0x1a/0x3a
> > > >  [<900e533c>] add_mtd_device+0x60/0xa0
> > > >  [<900e5f7e>] add_mtd_partitions+0x37a/0x3a0
> > > >  [<900ec4d0>] physmap_flash_probe+0x1ec/0x21c
> > > >  [<900e0f24>] platform_drv_probe+0x10/0x12
> > > >  [<900e06d0>] driver_probe_device+0x84/0xf0
> > > >  [<900e076a>] __driver_attach+0x2e/0x44
> > > >  [<900e0096>] bus_for_each_dev+0x2e/0x4c
> > > >  [<900e05b6>] driver_attach+0x12/0x14
> > > >  [<900e036c>] bus_add_driver+0x6c/0x178
> > > >  [<900e08a4>] driver_register+0x58/0xb0
> > > >  [<900e1126>] platform_driver_register+0x56/0x5c
> > > >  [<9000aaf6>] physmap_init+0xa/0x10
> > > >  [<9001422a>] do_one_initcall+0x2a/0x10c
> > > >  [<900005b8>] kernel_init+0x48/0x90
> > > >  [<9001fcc0>] do_exit+0x0/0x4cc
> > > 
> > > Ok, it turns out it's not related. It's a newly introduced regression
> > > which I've bisected down to:
> > > 
> > > commit abf5439370491dd6fbb4fe1a7939680d2a9bc9d4
> > > Author: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > > Date:   Sat Aug 16 14:10:05 2008 +0900
> > > 
> > >     block: move cmdfilter from gendisk to request_queue
> > 
> > Really sorry about that. A fix was queued in Jens' tree:
> > 
> > http://marc.info/?l=linux-kernel&m=122000748432301&w=2
> > 
> > 
> > > Unfortunately, I can't revert it cleanly, so it could be a false
> > > positive. But it does sort of make sense, since it makes the filter
> > > per-queue instead of per-gendisk, so if MTD uses the same queue for
> > > several block devices, the filter kobject might end up being
> > > initialized multiple times. Or something.
> > 
> > Right, the problem is that MTD uses the same queue for multiple
> > gendisks. It would be great if a MTD developer could fix it.
> 
> I'm also seeing it with drivers/block/ataflop.c (also a single queue) on
> ARAnyM.
> 
> And from looking at drivers/block/floppy.c and drivers/block/amiflop.c,
> I guess it happens there, too.
> 
> Any other single-queue drivers that got broken???

The pending change will eliminate this problem so that single queue
devices will work fine again. They should still work fine in -rc5, just
with the annoying WARN_ON() for each device per queue.

-- 
Jens Axboe