From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f70.google.com (mail-lf0-f70.google.com [209.85.215.70]) by kanga.kvack.org (Postfix) with ESMTP id 598CC280255 for ; Thu, 13 Oct 2016 07:43:43 -0400 (EDT) Received: by mail-lf0-f70.google.com with SMTP id d186so47251691lfg.7 for ; Thu, 13 Oct 2016 04:43:43 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q6si17165289wjy.190.2016.10.13.04.43.41 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 13 Oct 2016 04:43:41 -0700 (PDT) Date: Thu, 13 Oct 2016 11:44:41 +0200 From: Jan Kara Subject: Re: [PATCHv3 17/41] filemap: handle huge pages in filemap_fdatawait_range() Message-ID: <20161013094441.GC26241@quack2.suse.cz> References: <20160915115523.29737-1-kirill.shutemov@linux.intel.com> <20160915115523.29737-18-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160915115523.29737-18-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Theodore Ts'o , Andreas Dilger , Jan Kara , Andrew Morton , Alexander Viro , Hugh Dickins , Andrea Arcangeli , Dave Hansen , Vlastimil Babka , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org On Thu 15-09-16 14:54:59, Kirill A. Shutemov wrote: > We writeback whole huge page a time. This is one of the things I don't understand. Firstly I didn't see where changes of writeback like this would happen (maybe they come later). Secondly I'm not sure why e.g. writeback should behave atomically wrt huge pages. Is this because radix-tree multiorder entry tracks dirtiness for us at that granularity? BTW, can you also explain why do we need multiorder entries? What do they solve for us? I'm sorry for these basic questions but I'd just like to understand how is this supposed to work... Honza > > Signed-off-by: Kirill A. Shutemov > --- > mm/filemap.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 05b42d3e5ed8..53da93156e60 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -372,9 +372,14 @@ static int __filemap_fdatawait_range(struct address_space *mapping, > if (page->index > end) > continue; > > + page = compound_head(page); > wait_on_page_writeback(page); > if (TestClearPageError(page)) > ret = -EIO; > + if (PageTransHuge(page)) { > + index = page->index + HPAGE_PMD_NR; > + i += index - pvec.pages[i]->index - 1; > + } > } > pagevec_release(&pvec); > cond_resched(); > -- > 2.9.3 > > -- Jan Kara SUSE Labs, CR -- 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