From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boaz Harrosh Subject: Re: New TRIM/UNMAP tree published (2009-05-02) Date: Sun, 03 May 2009 19:34:14 +0300 Message-ID: <49FDC786.6070309@panasas.com> References: <1238683047-13588-1-git-send-email-willy@linux.intel.com> <49D8A3D7.5070507@panasas.com> <20090503061150.GF10704@linux.intel.com> <20090503071619.GP8822@parisc-linux.org> <20090503144847.GR8822@parisc-linux.org> <49FDB21B.3080301@panasas.com> <20090503154216.GU8822@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090503154216.GU8822@parisc-linux.org> Sender: linux-ide-owner@vger.kernel.org To: Matthew Wilcox Cc: Hugh Dickins , Matthew Wilcox , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Garzik , linux-scsi@vger.kernel.org, Jens Axboe , Bartlomiej Zolnierkiewicz , Mark Lord List-Id: linux-scsi@vger.kernel.org On 05/03/2009 06:42 PM, Matthew Wilcox wrote: > On Sun, May 03, 2009 at 06:02:51PM +0300, Boaz Harrosh wrote: >> I agree with Hugh. The allocation is done at, too-low in the food chain. >> (And that free of buffer at upper layer allocated by lower layer). >> >> I think you need to separate the: "does lld need buffer, what size" >> from the "here is buffer prepare", so upper layer that can sleep does >> sleep. > > So you want two function pointers in the request queue relating to discard? > OK I don't know what I want, I guess. ;-) I'm not a block-device export but from the small osdblk device I maintain it looks like osdblk_prepare_flush which is set into: blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH, osdblk_prepare_flush); does some internal structure setup, but the actual flush command is only executed later in the global osdblk_rq_fn which is set into: blk_init_queue(osdblk_rq_fn, &osdev->lock); But I'm not even sure that prepare_flush is called in a better context then queue_fn, and what does it means to let block devices take care of another new command type at queue_fn. I guess it comes back to Jeff Garzik's comment about not having a central place to ask the request what we need to do. But I do hate that allocation is done by driver and free by mid-layer, so yes two vectors, request_queue is allocated once per device it's not that bad. And later when Jeff's comment is addressed it can be removed. >> In all other buffer needing operations the allocation is done before >> submission of request, No? > > It's not true for the flush request (the example I quoted). Obviously, > the solution adopted here by IDE is Bad and Wrong ... > So now I don't understand, is flush executed by the queue_fn or by the prepare_flush, or am I seeing two type of flushes? Thanks Boaz