From: Bernd Schubert Subject: Re: bio_add_page rw mode check by merge_bvec_fn Date: Thu, 21 Nov 2013 19:08:25 +0100 Message-ID: <528E4C19.70507@itwm.fraunhofer.de> References: <528E4A50.7040609@itwm.fraunhofer.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Kent Overstreet , NeilBrown , Jens Axboe To: "linux-fsdevel@vger.kernel.org" , xfs@oss.sgi.com, linux-ext4@vger.kernel.org Return-path: Received: from mailgw1.uni-kl.de ([131.246.120.220]:38321 "EHLO mailgw1.uni-kl.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373Ab3KUSI2 (ORCPT ); Thu, 21 Nov 2013 13:08:28 -0500 In-Reply-To: <528E4A50.7040609@itwm.fraunhofer.de> Sender: linux-ext4-owner@vger.kernel.org List-ID: [CCing linux-fsdevel instead of accidental fhgfs cc] On 11/21/2013 07:00 PM, Bernd Schubert wrote: > Hi all, > > raid5_mergeable_bvec() (q->merge_bvec_fn) checks for the rw-type and > makes decisions based on that if the bio is mergable or not. But so far > this value is only initialized on calling submit_bio(), > at least not by ext4 and xfs. I have not checked other file system so far. > > Question 1: merge_bvec_fn is supposed to be removed, is is > still worth to fix the usage of merge_bvec_fn? > > Question 2: If it is still supposed to be fixed, how do want to have > it? So far I have two patches for xfs and ext4 to set the rw type > directly there, but maybe bio_add_page should get an int rw_type > parameter and set bio->bi_rw itself? > > > > diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c > index d488f80..4cddc15 100644 > --- a/fs/ext4/page-io.c > +++ b/fs/ext4/page-io.c > @@ -370,6 +370,7 @@ static int io_submit_init_bio(struct ext4_io_submit *io, > bio->bi_bdev = bh->b_bdev; > bio->bi_end_io = ext4_end_bio; > bio->bi_private = ext4_get_io_end(io->io_end); > + bio->bi_rw |= io->io_op; > io->io_bio = bio; > io->io_next_block = bh->b_blocknr; > return 0; > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 71c8c9d..b48048f 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -401,7 +401,8 @@ xfs_submit_ioend_bio( > > STATIC struct bio * > xfs_alloc_ioend_bio( > - struct buffer_head *bh) > + struct buffer_head *bh, > + struct writeback_control *wbc) > { > int nvecs = bio_get_nr_vecs(bh->b_bdev); > struct bio *bio = bio_alloc(GFP_NOIO, nvecs); > @@ -409,6 +410,7 @@ xfs_alloc_ioend_bio( > ASSERT(bio->bi_private == NULL); > bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); > bio->bi_bdev = bh->b_bdev; > + bio->bi_rw |= (wbc->sync_mode == WB_SYNC_ALL) ? WRITE_SYNC : WRITE; > return bio; > } > > @@ -511,7 +513,8 @@ xfs_submit_ioend( > > if (!bio) { > retry: > - bio = xfs_alloc_ioend_bio(bh); > + bio = xfs_alloc_ioend_bio(bh, wbc); > + > } else if (bh->b_blocknr != lastblock + 1) { > xfs_submit_ioend_bio(wbc, ioend, bio); > goto retry; > > > > Thanks, > Bernd >