Bug 31112

Created attachment 50852 [details]
Kernel log showing the problem

I noticed a bug with writes to block devices that disappeared (like removed USB sticks). The bug with introduced with:

commit aaead25b954879e1a708ff2f3602f494c18d20b5
Author: Christoph Hellwig <hch@lst.de>
Date:   Mon Oct 4 14:25:33 2010 +0200

    writeback: always use sb->s_bdi for writeback purposes

and I just checked that it is still present in v2.6.38. The last released version without that problem was v2.6.35.

Here are the steps I'm able to reproduce the problem:

- insert an USB stick with one partition and ext2 file system
- mount it: mount /dev/sdb1 /mnt
- open a handle to the stick: cat > /mnt/foo
- start writing to the file by pressing <Return> once
- remove the stick
- continue writing by pressing <Return> again
- kernel panic happens

I will attach the kernel log of the described session and the configuration I used for tracking it to the named commit.

The problem was already reported on lkml by other people:

- https://lkml.org/lkml/2011/2/28/272 (Patch included)
- https://lkml.org/lkml/2010/12/9/436

Torsten