linux-kernel - Re: [PATCH 1/2] f2fs: read with READ

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Message-id: <1361921882.31428.10.camel@kjgkr>
Date:	Wed, 27 Feb 2013 08:38:02 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] f2fs: read with READ_SYNC when getting dnode page

Hi,

2013-02-26 (화), 18:35 +0900, Namjae Jeon:
> 2013/2/26, Jaegeuk Kim <jaegeuk.kim@...sung.com>:
> > It must be set READ_SYNC not READA.
> Hi Jaegeuk.
> Could you please elaborate more?
> Why we need to change READA to READ_SYNC over here, when the purpose
> was to read the node page in READ ahead mode.

That point was a reason for me to make this bug before.
This is get_node_page_ra, not ra_node_page, which means that
ra_node_page does actual readahead for another node pages.

In summary, get_node_page_ra tries to:
1. grab or read a target node page for the given nid,
2. then, call ra_node_page to read other adjacent node pages in advance.

So, when we try to read a target node page by #1, we should submit bio
with READ_SYNC instead of READA.

I'll add this to the description.
Thanks,

> 
> Thanks.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> > ---
> >  fs/f2fs/node.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index e275218..185454f 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -930,7 +930,7 @@ repeat:
> >  	if (!page)
> >  		return ERR_PTR(-ENOMEM);
> >
> > -	err = read_node_page(page, READA);
> > +	err = read_node_page(page, READ_SYNC);
> >  	if (err) {
> >  		f2fs_put_page(page, 1);
> >  		return ERR_PTR(err);
> > --
> > 1.8.1.3.566.gaa39828
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >

-- 
Jaegeuk Kim
Samsung

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