From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kent Overstreet Subject: Re: [dm-devel] [PATCH v3 04/26] block: Refactor blk_update_request() Date: Tue, 2 Oct 2012 13:25:18 -0700 Message-ID: <20121002202518.GP26488@google.com> References: <1348526106-17074-1-git-send-email-koverstreet@google.com> <1348526106-17074-5-git-send-email-koverstreet@google.com> <20121002184359.GC3283@redhat.com> <20121002201014.GK26488@google.com> <20121002201451.GH758@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20121002201451.GH758-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Vivek Goyal Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org List-Id: dm-devel.ids On Tue, Oct 02, 2012 at 04:14:51PM -0400, Vivek Goyal wrote: > On Tue, Oct 02, 2012 at 01:10:14PM -0700, Kent Overstreet wrote: > > On Tue, Oct 02, 2012 at 02:43:59PM -0400, Vivek Goyal wrote: > > > On Mon, Sep 24, 2012 at 03:34:44PM -0700, Kent Overstreet wrote: > > > > Converts it to use bio_advance(), simplifying it quite a bit in the > > > > process. > > > > > > > > Note that req_bio_endio() now always calls bio_advance() - which means > > > > it always loops over the biovec, not just on partial completions. Don't > > > > expect it to affect performance, but worth noting. > > > > > > > > Tested it by forcing partial updates, and dumping before and after on > > > > various bio/bvec fields when doing a partial update. > > > > > > > > Signed-off-by: Kent Overstreet > > > > CC: Jens Axboe > > > > --- > > > > block/blk-core.c | 80 +++++++++----------------------------------------------- > > > > 1 file changed, 12 insertions(+), 68 deletions(-) > > > > > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > > index a17869f..a8a1a9e 100644 > > > > --- a/block/blk-core.c > > > > +++ b/block/blk-core.c > > > > @@ -158,20 +158,10 @@ static void req_bio_endio(struct request *rq, struct bio *bio, > > > > else if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) > > > > error = -EIO; > > > > > > > > - if (unlikely(nbytes > bio->bi_size)) { > > > > - printk(KERN_ERR "%s: want %u bytes done, %u left\n", > > > > - __func__, nbytes, bio->bi_size); > > > > - nbytes = bio->bi_size; > > > > - } > > > > - > > > > > > You are dropping this warning because nobody is calling req_bio_endio() > > > with bytes greater than bio size in current code? > > > > Not dropping it, just moved it to bio_advance() > > bio_advance() is checking bio vec count and idx and not nr_bytes. Whoops, -ENOCOFFEE... I didn't fully read that code fragment. Yes, req_bio_endio() is only called from one place, and blk_update_request() never calls it with nbytes > bio->bi_size (and after the refactor it's more obviously impossible).