On Sun, 2010-11-21 at 18:57 +0100, Andi Kleen wrote:
> Alexander Kolesen <kolesen.a@xxxxxxxxx> writes:
>
> [Rafael, a new regression]
>
> > Hello.
> > I've built a kernel from
> > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
> > (Date: Fri Nov 19 19:46:45 2010 -0800)
> > and got a kernel oops when tried to access to unplugged,
> > but mounted external usb storage formatted with JFS.
>
> Al seems to be the last person who touched it, maybe it's
> related to his changes, like this one.
>
> commit 152a08366671080f27b32e0c411ad620c5f88b57
> Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Date: Sun Jul 25 00:46:55 2010 +0400
>
> new helper: mount_bdev()
>
> ... and switch of the obvious get_sb_bdev() users to ->mount()
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
I haven't dug too far into this yet, but I suspect that
aaead25b954879e1a708ff2f3602f494c18d20b5 is related.
commit aaead25b954879e1a708ff2f3602f494c18d20b5
Author: Christoph Hellwig <hch@xxxxxx>
Date: Mon Oct 4 14:25:33 2010 +0200
writeback: always use sb->s_bdi for writeback purposes
I'll have to look at what happens when a device is unplugged to see if
JFS is missing something, or it's more of a generic problem. I'm open
to suggestions from anybody on cc.
Thanks,
Shaggy
>
> >
> > Steps to reproduce:
> > mkfs.jfs /dev/sdb1 (unpluggable USB hard drive)
> > mount /dev/sdb1 /mnt/drive
> > cd /mnt/drive
> > touch test
> > sync
> > ..unplug a drive
> > ls
> >
> >
> > Result:
> > BUG: unable to handle kernel NULL pointer dereference at
> > 0000000000000020
> > IP: __mark_inode_dirty
> >
> > Then I got a kernel coredump. Here is a stack trace:
> >
> > (gdb) bt
> > #0 __mark_inode_dirty (inode=0xffff880078fc1490, flags=<value optimized out>) at fs/fs-writeback.c:990
> > #1 0xffffffff810e4990 in mark_inode_dirty_sync (mnt=0xffff88007862fd00, dentry=<value optimized out>) at include/linux/fs.h:1687
> > #2 touch_atime (mnt=0xffff88007862fd00, dentry=<value optimized out>) at fs/inode.c:1505
> > #3 0xffffffff810dfeb4 in file_accessed (file=0xffff88006afed600, filler=0xffffffff810dfcf8 <filldir>, buf=0xffff88007762bf38) at include/linux/fs.h:1763
> > #4 vfs_readdir (file=0xffff88006afed600, filler=0xffffffff810dfcf8 <filldir>, buf=0xffff88007762bf38) at fs/readdir.c:41
> > #5 0xffffffff810e001a in sys_getdents (fd=<value optimized out>, dirent=0x1f61468, count=32768) at fs/readdir.c:214
> > #6 0xffffffff810279ab in ?? () at arch/x86/kernel/entry_64.S:479
> > #7 0x00007f8b23d1a4c5 in ?? ()
> > #8 0x00000000000002bb in ?? ()
> > #9 0x0000000000000000 in ?? ()
> >
> > (gdb) p bdi
> > $1 = (struct backing_dev_info *) 0x0
> >
> > (gdb) p inode->i_mapping->backing_dev_info
> > $15 = (struct backing_dev_info *) 0xffff880078878d48
> >
> > (gdb) p inode->i_sb->s_bdi
> > $16 = (struct backing_dev_info *) 0x0
> >
> >
> > I can't do git bisect because on n'th step my system became unbootable.
> > But 2.6.35 doesn't fall.
--
Dave Kleikamp
IBM Linux Technology Center
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