From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754595Ab0F0J1d (ORCPT ); Sun, 27 Jun 2010 05:27:33 -0400 Received: from verein.lst.de ([213.95.11.210]:53150 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753193Ab0F0J1c (ORCPT ); Sun, 27 Jun 2010 05:27:32 -0400 Date: Sun, 27 Jun 2010 11:26:52 +0200 From: Christoph Hellwig To: FUJITA Tomonori Cc: snitzer@redhat.com, hch@lst.de, axboe@kernel.dk, dm-devel@redhat.com, James.Bottomley@suse.de, linux-kernel@vger.kernel.org, martin.petersen@oracle.com, akpm@linux-foundation.org Subject: Re: [PATCH 1/2] block: fix leaks associated with discard request payload Message-ID: <20100627092652.GA11625@lst.de> References: <20100622180029.GA15950@redhat.com> <1277582211-10725-1-git-send-email-snitzer@redhat.com> <20100627174721D.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100627174721D.fujita.tomonori@lab.ntt.co.jp> User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 27, 2010 at 05:49:29PM +0900, FUJITA Tomonori wrote: > On Sat, 26 Jun 2010 15:56:50 -0400 > Mike Snitzer wrote: > > > Fix leaks introduced via "block: don't allocate a payload for discard > > request" commit a1d949f5f44. > > > > sd_done() is not called for REQ_TYPE_BLOCK_PC commands so cleanup > > discard request's payload directly in scsi_finish_command(). > > Instead of adding another discard hack to scsi_finish_command(), how > about converting discard to REQ_TYPE_FS request? discard is FS request > from the perspective of the block layer. It also fixes a problem that > discard isn't retried in the case of UNIT ATTENTION. > > I think that we can get more cleaner code if we handle discard as > normal (fs) request in the block layer (and scsi-ml). We need more > changes but this patch is the first step. Making discard a REQ_TYPE_FS inside scsi (it already is before entering sd_prep_fn) means we'll need to special case it all over the I/O submission and completion path. Having the payload length not matching the transfer length is something we don't expect for FS requests. > index e16185b..9e15c46 100644 > --- a/block/blk-lib.c > +++ b/block/blk-lib.c > @@ -20,6 +20,10 @@ static void blkdev_discard_end_io(struct bio *bio, int err) > if (bio->bi_private) > complete(bio->bi_private); > > + /* free the page that the lower layer allocated */ > + if (bio_page(bio)) > + __free_page(bio_page(bio)); > + This is exactly what this patchkit gets rid off. Having a payload page that the caller tracks (previously fully, with this patch only for freeing) makes DM's life a lot harder. Remember we don't actually store any payload in there before entering sd_prep_fn - it's just that the scsi commands implementing discards need some payload - either a sector sizes zero filled buffer for WRITE SAME, or an LBA/len encoding inside the payload for UNMAP. > - rq->cmd_type = REQ_TYPE_BLOCK_PC; > + rq->cmd_type = REQ_TYPE_FS; No need to set REQ_TYPE_FS here, it's already set up that way.