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SubjectRe: fs: Inode cache scalability V3
On Wed, Oct 13, 2010 at 05:46:09PM -0400, Christoph Hellwig wrote:
> On Wed, Oct 13, 2010 at 11:58:45AM -0400, Christoph Hellwig wrote:
> >
> > It's 100% reproducible on my kvm VM. The bug is the assert_spin_locked
> > in redirty_tail. I really can't find a way how we reach it without
> > d_lock so this really confuses me.
> We are for some reason getting a block device inode that is on the
> dirty list of a bdi that it doesn't point to. Still trying to figure
> out how exactly that happens.

It's because __blkdev_put reset the bdi on the mapping, and bdev inodes
are still special cased to not use s_bdi unlike everybody else. So
we keep switch between different bdis that get locked.

I wonder what's a good workaround for that. Just flushing out all
dirty state of a block device inode on last close would fix, but we'd
still have all the dragons hidden underneath until we finally sort
out the bdi reference mess.

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