linux-kernel - Re: [PATCH v2 01/17] mm: drop "wait" parameter from write_one

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Date:   Wed, 12 Apr 2017 10:34:46 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, tytso@....edu, jack@...e.cz,
        neilb@...e.com, viro@...iv.linux.org.uk
Subject: Re: [PATCH v2 01/17] mm: drop "wait" parameter from write_one_page

On Wed, 2017-04-12 at 07:27 -0700, Matthew Wilcox wrote:
> On Wed, Apr 12, 2017 at 08:05:58AM -0400, Jeff Layton wrote:
> > The callers all set it to 1. Also, make it clear that this function will
> > not set any sort of AS_* error, and that the caller must do so if
> > necessary. No existing caller uses this on normal files, so none of them
> > need it.
> 
> So ... anyone who doesn't check the error code loses an error indication.
> 
> > +++ b/fs/jfs/jfs_metapage.c
> > @@ -711,7 +711,7 @@ void force_metapage(struct metapage *mp)
> >  	get_page(page);
> >  	lock_page(page);
> >  	set_page_dirty(page);
> > -	write_one_page(page, 1);
> > +	write_one_page(page);
> >  	clear_bit(META_forcewrite, &mp->flag);
> >  	put_page(page);
> >  }
> > @@ -756,7 +756,7 @@ void release_metapage(struct metapage * mp)
> >  		set_page_dirty(page);
> >  		if (test_bit(META_sync, &mp->flag)) {
> >  			clear_bit(META_sync, &mp->flag);
> > -			write_one_page(page, 1);
> > +			write_one_page(page);
> >  			lock_page(page); /* write_one_page unlocks the page */
> >  		}
> >  	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
> 
> This looks quite bad.  If my reading is right, these pages are part of
> the journal.  I think somebody who knows JFS needs to figure out what
> should happen here ...
> 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 00a8fa7e366a..f25b76486645 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2187,7 +2187,7 @@ extern void filemap_map_pages(struct vm_fault *vmf,
> >  extern int filemap_page_mkwrite(struct vm_fault *vmf);
> >  
> >  /* mm/page-writeback.c */
> > -int write_one_page(struct page *page, int wait);
> > +int write_one_page(struct page *page);
> >  void task_dirty_inc(struct task_struct *tsk);
> >  
> >  /* readahead.c */
> 
> Can we mark this as __must_check so JFS picks up a couple of warnings?
> 
> Reviewed-by: Matthew Wilcox <mawilcox@...rosoft.com>

Good idea -- I'll roll that in with this patch.
-- 
Jeff Layton <jlayton@...hat.com>