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SubjectRe: 2.6.28-rc2: (mtd)block/partitions BUG with kobject reference count
On Fri, Oct 31, 2008 at 7:47 AM, Kay Sievers <kay.sievers@vrfy.org> wrote:
> On Thu, Oct 30, 2008 at 22:51, Kay Sievers <kay.sievers@vrfy.org> wrote:
>> On Thu, Oct 30, 2008 at 00:28, Peter Korsgaard <jacmet@sunsite.dk> wrote:
>>>>>>>> "Rafael" == Rafael J Wysocki <rjw@sisk.pl> writes:
>>>
>>> Rafael> On Wednesday, 29 of October 2008, Peter Korsgaard wrote:
>>> >> Hi,
>>> >>
>>> >> I'm seing what looks like a kobject reference count issue with
>>> >> mtdblock_ro + mtd_dataflash + mtd partitions and repeated unbind/bind.
>>> >> I'm on 2.6.28-rc2, but I can reproduce the problem on 2.6.27 as well.
>>>
>>> Rafael> Is it reproducible with 2.6.26 too?
>>>
>>> Sorry, I haven't backported my platform support code to such "old"
>>> kernel. I can do it though, if you think it will help pinpoint the
>>> issue.
>>
>> This sounds like a possible reason for the problem:
>> "After digging into the mtd code, this bug is not related to our driver. It
>> should be a subtle bug in mtd core code.
>>
>> In add_mtd_partition, for 2 partitions, 2 gendisk structures will be
>> allocated. But these 2 gendisk->queue will be set to the same
>> request_queue. Then when unregistering the 1st partition, from the
>> same request_queue->backing_dev_info, the bdi struct will be set to
>> NULL. So for the 2nd partition (bdi == NULL), the sysfs dir of 2nd
>> partition will not be removed. Finally, when modprobe the module
>> again, the 2nd partition won't be added"
>> https://blackfin.uclinux.org/gf/tracker/4463
>
> Looks like a bdi issue:
> http://lkml.org/lkml/2008/10/30/519
>
> Peter, if I do this (whitespace mangled, just pasted in here), the
> error goes away for me. Can you try this?
>
> Thanks,
> Kay
>
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -515,7 +515,8 @@ void add_disk(struct gendisk *disk)
> blk_register_queue(disk);
>
> bdi = &disk->queue->backing_dev_info;
> - bdi_register_dev(bdi, disk_devt(disk));
> + if (!bdi->dev)
> + bdi_register_dev(bdi, disk_devt(disk));
> retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
> "bdi");
> WARN_ON(retval);

IMHO, this is a workaround, right? I think the final solution should
provide every 'gendisk' a dedicated 'bdi'.
So they won't mess up and overwrite.

-Bryan


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