From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: memory allocation in sg_io() Date: Thu, 10 Jan 2008 14:06:28 +0100 Message-ID: <20080110130628.GA6258@kernel.dk> References: <200801101333.12293.oliver@neukum.org> <47861815.5090008@panasas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from brick.kernel.dk ([87.55.233.238]:26966 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752491AbYAJNGb (ORCPT ); Thu, 10 Jan 2008 08:06:31 -0500 Content-Disposition: inline In-Reply-To: <47861815.5090008@panasas.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Boaz Harrosh Cc: Oliver Neukum , SCSI development list On Thu, Jan 10 2008, Boaz Harrosh wrote: > On Thu, Jan 10 2008 at 14:33 +0200, Oliver Neukum wrote: > > Hi, > > > > could you explain to me why this code can get away with allocating the > > sense buffer on the stack? > > > > static int sg_io(struct file *file, struct request_queue *q, > > struct gendisk *bd_disk, struct sg_io_hdr *hdr) > > { > > unsigned long start_time; > > int writing = 0, ret = 0, has_write_perm = 0; > > struct request *rq; > > char sense[SCSI_SENSE_BUFFERSIZE]; > > > > Regards > > Oliver > > - > where? what? do you mean in scsi_ioctl.c? > why not it's a synchronous call? > Do you mean 96 bytes is too big? > Do you mean DMA alignment and cache coherency? I'm working > on that for scsi devices. I'm guessing aligment - so the answer is that 'it cannot get away with it'. -- Jens Axboe