linux-kernel - Re: [PATCH 2/2] mm: filemap: Avoid unnecessary calls to lock_page when waiting for IO to complete during a read

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Date:	Mon, 25 Jan 2016 14:05:06 +0000
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Jan Kara <jack@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm: filemap: Avoid unnecessary calls to lock_page
 when waiting for IO to complete during a read

On Mon, Jan 25, 2016 at 12:35:13PM +0100, Jan Kara wrote:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>
> 

Thanks!

> > ---
> >  mm/filemap.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> > 
> > diff --git a/mm/filemap.c b/mm/filemap.c
> > index aa38593d0cd5..235ee2b0b5da 100644
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -1649,6 +1649,15 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
> >  					index, last_index - index);
> >  		}
> >  		if (!PageUptodate(page)) {
> > +			/*
> > +			 * See comment in do_read_cache_page on why
> > +			 * wait_on_page_locked is used to avoid unnecessarily
> > +			 * serialisations and why it's safe.
> > +			 */
> > +			wait_on_page_locked(page);
> > +			if (PageUptodate(page))
> > +				goto page_ok;
> > +
> 
> We want a wait_on_page_locked_killable() here to match the
> lock_page_killable() later in do_generic_file_read()?
> 

Yes, I'll fix it in v2.

-- 
Mel Gorman
SUSE Labs