From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alasdair G Kergon Subject: Re: [dm-devel] [PATCH v10 1/8] block: Generalized bio pool freeing Date: Tue, 18 Sep 2012 17:31:57 +0100 Message-ID: <20120918163156.GC17356@agk-dp.fab.redhat.com> References: <1346970902-10931-1-git-send-email-koverstreet@google.com> <1346970902-10931-2-git-send-email-koverstreet@google.com> <20120914182828.GK15728@agk-dp.fab.redhat.com> <20120917205139.GB14492@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120917205139.GB14492-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Kent Overstreet Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Jens Axboe , Lars Ellenberg , Hannes Reinecke List-Id: linux-bcache@vger.kernel.org On Mon, Sep 17, 2012 at 01:51:39PM -0700, Kent Overstreet wrote: > That isn't a very good patch - it says it's clearing bi_end_io as a > precaution, but as a precaution to what? As a precaution against the endio function being called an extra time by mistake if a stray reference remains after the bio has been freed. Wipe this field when dm frees it. Defensive programming, basically, in response to a tricky bug he had to deal with. Alasdair