Messages in this thread | | | Date | Mon, 16 Apr 2012 20:17:18 +0100 | From | Al Viro <> | Subject | Re: mtdchar kernel oops |
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On Mon, Apr 16, 2012 at 02:37:06PM +0200, Joel Reardon wrote: > The troubled asm pair corresponds to this line: > this_cpu_add(mnt->mnt_pcp->mnt_count, n) in the inline mnt_add_count(). > So I suppose that perhaps either mnt is bad, or mnt_pcp is bad. > > I'm using nandsim to simulate the mtd device. Steps are simple, load the > modules: > nand_ecc nand nand_ids mtd mtd_blkdevs mtdblock mtdchar > nandsim first_id_byte=0x20 second_id_byte=0xa5 third_id_byte=0x00 fourth_id_byte=0x15 parts=0xa40 rptwear=1000 > > then `ubiformat /dev/mtd0` does the oops.
Not here:
root@dizzy:~# modprobe nandsim first_id_byte=0x20 second_id_byte=0xa5 third_id_byte=0x00 fourth_id_byte=0x15 parts=0xa40 rptwear=1000 ubiformat: mtd0 (nand), size 343932928 bytes (328.0 MiB), 2624 eraseblocks of 131072 bytes (128.0 KiB), min. I/O size 2048 bytes libscan: scanning eraseblock 2623 -- 100 % complete ubiformat: 2624 eraseblocks are supposedly empty ubiformat: formatting eraseblock 2623 -- 100 % complete root@dizzy:~# uname -a Linux dizzy 3.4.0-rc2+ #4 SMP Mon Apr 16 15:04:25 EDT 2012 x86_64 GNU/Linux
and no oopsen in sight...
> > Could you add printk into mtdchar_open(), dumping mnt and count values > > right after simple_pin_fs() call? > > > > It oopses before it returns from the simple_pin_fs call, so that won't be > possible...
Wha...? You mean, that happens on the _first_ simple_pin_fs() call? But that makes no damn sense whatsoever - we just do vfs_kern_mount(), get a vfsmount from it (and not an ERR_PTR(), at that), then store it into mnt and do mntget(mnt) followed by mntput(mnt). If that really happens when simple_pin_fs() gets called with mnt == NULL and count == 0, we have much bigger problem on hands...
Please, slap such printks before and after simple_pin_fs() in mtdchar_open() and before and after simple_release_fs() in mtdchar_close(). And verify that you have commit c65390f4dd49755863f6d772ec538ee4757c08d7 in your tree.
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