linux-kernel - RE: [f2fs-dev][PATCH 6/6] f2fs: add a tracepoint for f2fs_read_data

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Message-id: <000001cf6a9b$d9d14740$8d73d5c0$@samsung.com>
Date:	Thu, 08 May 2014 16:58:57 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	jaegeuk.kim@...sung.com
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: RE: [f2fs-dev][PATCH 6/6] f2fs: add a tracepoint for
 f2fs_read_data_pages

Hi Kim,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk.kim@...sung.com]
> Sent: Wednesday, May 07, 2014 8:30 AM
> To: Chao Yu
> Cc: linux-f2fs-devel@...ts.sourceforge.net; linux-fsdevel@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [f2fs-dev][PATCH 6/6] f2fs: add a tracepoint for f2fs_read_data_pages
> 
> Hi Chao,
> 
> 2014-05-06 (화), 16:54 +0800, Chao Yu:
> > This patch adds a tracepoint for f2fs_read_data_pages to trace when pages are
> > readahead by VFS.
> >
> > Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> > ---
> >  fs/f2fs/data.c              |    3 +++
> >  include/trace/events/f2fs.h |   26 ++++++++++++++++++++++++++
> >  2 files changed, 29 insertions(+)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 8c250a5..f2d1e8a 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -729,6 +729,9 @@ static int f2fs_read_data_pages(struct file *file,
> >  			struct list_head *pages, unsigned nr_pages)
> >  {
> >  	struct inode *inode = file->f_mapping->host;
> > +	struct page *page = list_entry(pages->prev, struct page, lru);
> 
> IMO, it needs to avoid the above line.

Maybe it’s not safe to access page directly in lru list here.
Let's ignore this patch.
Thanks.

> Thanks,
> 
> > +
> > +	trace_f2fs_readpages(inode, page, nr_pages);
> >
> >  	/* If the file has inline data, skip readpages */
> >  	if (f2fs_has_inline_data(inode))
> > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > index b983990..7fbaaaa 100644
> > --- a/include/trace/events/f2fs.h
> > +++ b/include/trace/events/f2fs.h
> > @@ -847,6 +847,32 @@ TRACE_EVENT(f2fs_writepages,
> >  		__entry->for_sync)
> >  );
> >
> > +TRACE_EVENT(f2fs_readpages,
> > +
> > +	TP_PROTO(struct inode *inode, struct page *page, unsigned int nrpage),
> > +
> > +	TP_ARGS(inode, page, nrpage),
> > +
> > +	TP_STRUCT__entry(
> > +		__field(dev_t,	dev)
> > +		__field(ino_t,	ino)
> > +		__field(pgoff_t,	start)
> > +		__field(unsigned int,	nrpage)
> > +	),
> > +
> > +	TP_fast_assign(
> > +		__entry->dev	= inode->i_sb->s_dev;
> > +		__entry->ino	= inode->i_ino;
> > +		__entry->start	= page->index;
> > +		__entry->nrpage	= nrpage;
> > +	),
> > +
> > +	TP_printk("dev = (%d,%d), ino = %lu, start = %lu nrpage = %u",
> > +		show_dev_ino(__entry),
> > +		(unsigned long)__entry->start,
> > +		__entry->nrpage)
> > +);
> > +
> >  TRACE_EVENT(f2fs_submit_page_mbio,
> >
> >  	TP_PROTO(struct page *page, int rw, int type, block_t blk_addr),
> 
> --
> Jaegeuk Kim
> Samsung

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