From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH 1/2] block: Modify blk_rq_map_user to support large requests Date: Wed, 13 Sep 2006 14:38:08 -0500 Message-ID: <45085E20.7070003@cs.wisc.edu> References: <1157835221.4543.10.camel@max> <20060913093009.GF23515@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20060913093009.GF23515@kernel.dk> Sender: linux-kernel-owner@vger.kernel.org To: Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Jens Axboe wrote: > On Sat, Sep 09 2006, Mike Christie wrote: >> Currently, there is some duplication between bsg, scsi_ioctl.c >> and scsi_lib.c/sg/st in its mapping code. This patch modifies >> the block layer blk_rq_map_user code to support large requests so >> that the scsi and block drivers can use this common code. The >> changes also make it so the callers do not have to account for >> the bio to be unmapped and bounce buffers. >> >> The next patch then coverts bsg.c, scsi_ioctl.c and cdrom.c >> to use the updated functions. For scsi_ioctl.c and cdrom.c >> the only thing that changes is that they no longer have >> to do the bounce buffer management and pass in the len for >> the unmapping. The bsg change is a little larger since that >> code was duplicating a lot of code that is now common >> in the block layer. The bsg conversions als should fix >> a memory leak caused when unmapping a hdr with iovec_count=0. >> >> Patch was made over Jens's block tree and the bsg branch > > Generally it looks good - two comments: > > - I see some advantages to having biohead_orig to avoid keeping track of > it and passing it around, but there's also good reasons for _not_ > adding more stuff to struct request. Any particular reason you chose > to do that? I think I originally made a mistake with the bounce buffers and thinking that others may do the same I felt that hiding a lot of the magic that is going on in blk_rq_map_user was nice. By adding the field to the request, the caller would only have to map the data and then unmap the request. Since not even a handful of drivers would ever use the api, I agree that adding the field for this limited use could be overkill. > > - blk_get_bounced_bio() looks redundant. BIO_BOUNCED should only be set > on a bounced bio, and ->bi_private should always hold that bounced > bio. > Ok, I will remove that.