From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alasdair G Kergon Subject: Re: [dm-devel] [PATCH 2/2] block: Avoid deadlocks with bio allocation by stacking drivers Date: Tue, 11 Sep 2012 00:45:34 +0100 Message-ID: <20120910234534.GD10477@agk-dp.fab.redhat.com> References: <20120910202435.GG16360@google.com> <20120910204010.GA32310@google.com> <20120910213349.GH16360@google.com> <20120910213710.GA7677@google.com> <20120910215633.GA19739@google.com> <20120910220910.GB7677@google.com> <20120910225057.GA10477@agk-dp.fab.redhat.com> <20120910230917.GB10477@agk-dp.fab.redhat.com> <20120910233502.GH7677@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120910233502.GH7677-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Tejun Heo Cc: Kent Overstreet , axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, device-mapper development , david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mikulas Patocka , bharrosh-C4P08NqkoRlBDgjK7y7TUQ@public.gmane.org, Vivek Goyal List-Id: linux-bcache@vger.kernel.org On Mon, Sep 10, 2012 at 04:35:02PM -0700, Tejun Heo wrote: > debug. Would it be difficult to convert dm drivers to collect size > requirements and use front-pad for all per-bio data? I can't give a quick answer because a single bio may require a variable number (depending on the bio content) of (sequential) mempool_allocs from the same mempool to complete its processing, so we do have to audit all this very carefully to see what can/can't be pulled out. Alasdair