Messages in this thread | | | Date | Wed, 22 Oct 2008 11:24:10 +0800 | From | "Bryan Wu" <> | Subject | Re: [BUG] re-modprobe a nand controller driver module will cause system crash. |
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Hi folks,
Did anyone meet this issue before?
-Bryan
On Thu, Oct 16, 2008 at 6:56 PM, Bryan Wu <cooloney@kernel.org> wrote: > Hi folks, > > These days I found a subtle bug which should be related with mtdcore layers. > The detailed story is located at > https://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?action=TrackerItemEdit&tracker_id=141&tracker_item_id=4463. > > Briefly speaking, > 1) modprobe a nand controller driver to add_mtd_paritition(). > 2) add_mtd_partition->add_devices->blktrans_notify_add->mtdblock_add_mtd->add_mtd_blktrans_dev > 3) in add_mtd_blktrans_dev, alloc_disk will be called to create a new > gendisk structure according to the partition setting. > 4) "gd->queue = tr->blkcore_priv->rq;" > No matter how many partitions (in my test, 2 partitions), there > will be the same number gendisk structures but just 1 queue. > They all use the same request_queue which is created in > register_mtd_blktrans. > 5) mtdblockd kthread handles this request_queue for mtdblock layer. > 6) There is one backing_dev_info structure member (not pointer) in > request_queue. so for several mtd partitions (serveral gendisks) there > is only one bdi structure instance. > 7) So the problem is in add_disk(), > bdi_register_dev(bdi, MKDEV(disk->major, disk->first_minor)); > For 1st partition mtdblock0, it will create /sys/class/bdi/31:0 > and register information in bdi structure instance. > Then for 2nd partition mtdblock1, because the bdi structure > instance is the same as the 1st partition, it will overwrite bdi > structure and create /sys/class/bdi/31:1. > So the bdi info of 1st partition are totally lost. > 8) When we rmmod the nand controller driver, del_mtd_partition will > only remove /sys/class/bdi/31:1 but left 1st partition > /sys/class/bdi/31:0 there. > 9) modprobe again will let the bug show up. > > I found this bug does not relate with my nand flash controller driver > and it should be fixed in mtdblock layer. > And if we just add only one partition, there is no such bug at all. I > tried to solve this bug, but it related with > mtdblock/mtd_blktrans/block/bdi. It is diffcult for me to find a way > to satisfy all the parts with minimal changes. > > IMHO, can we just simply remove the bdi_register_dev (in add_disk) and > bdi_unregister_dev (in unlink_disk)? > > P.S. I also found this bug in latest 2.6.27 kernel mainline. > > Thanks > -Bryan >
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