From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx188.postini.com [74.125.245.188]) by kanga.kvack.org (Postfix) with SMTP id 32FE06B005A for ; Mon, 17 Sep 2012 15:16:27 -0400 (EDT) Received: by qcsd16 with SMTP id d16so5945444qcs.14 for ; Mon, 17 Sep 2012 12:16:26 -0700 (PDT) Date: Mon, 17 Sep 2012 12:15:46 -0700 (PDT) From: Hugh Dickins Subject: Re: Does swap_set_page_dirty() calling ->set_page_dirty() make sense? In-Reply-To: <20120917163518.GD9150@quack.suse.cz> Message-ID: References: <20120917163518.GD9150@quack.suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Mel Gorman , linux-mm@kvack.org On Mon, 17 Sep 2012, Jan Kara wrote: > > I tripped over a crash in reiserfs which happened due to PageSwapCache > page being passed to reiserfs_set_page_dirty(). Now it's not that hard to > make reiserfs_set_page_dirty() check that case but I really wonder: Does it > make sense to call mapping->a_ops->set_page_dirty() for a PageSwapCache > page? The page is going to be written via direct IO so from the POV of the > filesystem there's no need for any dirtiness tracking. Also there are > several ->set_page_dirty() implementations which will spectacularly crash > because they do things like page->mapping->host, or call > __set_page_dirty_buffers() which expects buffer heads in page->private. > Or what is the reason for calling filesystem's set_page_dirty() function? This is a question for Mel, really: it used not to call the filesystem. But my reading of the 3.6 code says that it still will not call the filesystem, unless the filesystem (only nfs) provides a swap_activate method, which should be the only case in which SWP_FILE gets set. And I rather think Mel does want to use the filesystem set_page_dirty in that case. Am I misreading? Did you see this on a vanilla kernel? Or is it possible that you have a private patch merged in, with something else sharing the SWP_FILE bit (defined in include/linux/swap.h) by mistake? Hugh > [PATCH] mm: Remove swap_set_page_dirty() > > It doesn't make much sense to call filesystem's ->set_page_dirty() method for > PageSwapCache page. It will be written through direct IO so filesystem doesn't > care about its dirtiness and several filesystems actually don't count with such > pages getting into their ->set_page_dirty() functions. > > Signed-off-by: Jan Kara > --- > mm/page_io.c | 12 ------------ > mm/swap_state.c | 2 +- > 2 files changed, 1 insertions(+), 13 deletions(-) > > diff --git a/mm/page_io.c b/mm/page_io.c > index 78eee32..8520a4f 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -278,15 +278,3 @@ int swap_readpage(struct page *page) > out: > return ret; > } > - > -int swap_set_page_dirty(struct page *page) > -{ > - struct swap_info_struct *sis = page_swap_info(page); > - > - if (sis->flags & SWP_FILE) { > - struct address_space *mapping = sis->swap_file->f_mapping; > - return mapping->a_ops->set_page_dirty(page); > - } else { > - return __set_page_dirty_no_writeback(page); > - } > -} > diff --git a/mm/swap_state.c b/mm/swap_state.c > index 0cb36fb..01852cd 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -27,7 +27,7 @@ > */ > static const struct address_space_operations swap_aops = { > .writepage = swap_writepage, > - .set_page_dirty = swap_set_page_dirty, > + .set_page_dirty = set_page_dirty_no_writeback, > .migratepage = migrate_page, > }; > > -- > 1.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org