Re: [PATCH 2/4] AFS: Add a function to excise a rejected write from the pagecache

[David Howells <dhowells@redhat.com>]

Andrew Morton <akpm@linux-foundation.org> wrote:

> So my reason for asking the above is to try to find a way to make all these
> new PG-error games just go away.

Yeah.  However, there needs to be something to cover the gap between releasing
PG_writeback and getting PG_lock.  They have to be done in that order to avoid
deadlocking against truncate and other stuff, but that leaves a window in which
the page appears to be in a good state - one in which prepare_write() or
page_mkwrite() can potentially leak through.

Nick Piggin talked about using an extra lock, but as far as I can tell, that
just compounds the deadlock problems.

I suppose I could leave something in page->private that indicated that the
page was defunct, but that'd have to be done by the filesystem, probably
before calling cancel_rejected_write().

David