linux-kernel - Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add

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Message-ID: <20120730153935.GE4547@phenom.dumpdata.com>
Date:	Mon, 30 Jul 2012 11:39:35 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	majianpeng <majianpeng@...il.com>
Cc:	axboe <axboe@...nel.dk>, "chris.mason" <chris.mason@...ionio.com>,
	viro <viro@...IV.linux.org.uk>, tytso <tytso@....edu>,
	"adilger.kernel" <adilger.kernel@...ger.ca>,
	shaggy <shaggy@...nel.org>, mfasheh <mfasheh@...e.com>,
	jlbec <jlbec@...lplan.org>, bpm <bpm@....com>,
	elder <elder@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	jfs-discussion <jfs-discussion@...ts.sourceforge.net>,
	ocfs2-devel <ocfs2-devel@....oracle.com>, xfs <xfs@....sgi.com>
Subject: Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.

On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote:
> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page,

What about submit_bio? That sets the bi_rw as well?
> it will use bi_rw.
> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn().

function.
> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge.
> >> if ((bvm->bi_rw & 1) == WRITE)
> >> return biovec->bv_len; /* always allow writes to be mergeable */

So what does that mean? Without this patch what happens?

> 
> 
> Jianpeng Ma (8):

Can you collapse all of this in just one patch?

>   Evalue bio->bi_rw after calling bio_alloc() and before calling

It is 'evaluate'
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>     bio_add_page().
> 
>  block/blk-lib.c                     |    1 +
>  drivers/block/xen-blkback/blkback.c |    1 +

I am not really sure if that is correct. Does 'submit_bio' not do the
job properly?

>  fs/btrfs/check-integrity.c          |    1 +
>  fs/direct-io.c                      |    1 +
>  fs/ext4/page-io.c                   |    1 +
>  fs/jfs/jfs_metapage.c               |    1 +
>  fs/ocfs2/cluster/heartbeat.c        |    8 +++++---
>  fs/xfs/xfs_aops.c                   |    2 ++
>  fs/xfs/xfs_buf.c                    |    1 +
>  9 files changed, 14 insertions(+), 3 deletions(-)
> 
> -- 
> 1.7.9.5
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