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From: Suparna Bhattacharya <suparna@in.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: daniel@osdl.org, janetmor@us.ibm.com, pbadari@us.ibm.com,
	linux-aio@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch
Date: Wed, 31 Dec 2003 15:39:49 +0530	[thread overview]
Message-ID: <20031231100949.GA4099@in.ibm.com> (raw)
In-Reply-To: <20031231015913.34fc0176.akpm@osdl.org>

On Wed, Dec 31, 2003 at 01:59:13AM -0800, Andrew Morton wrote:
> Suparna Bhattacharya <suparna@in.ibm.com> wrote:
> >
> > > If you are referring to this code in mpage_writepage():
> >  > 
> >  > 		lock_page(page);
> >  > 
> >  > 		if (wbc->sync_mode != WB_SYNC_NONE)
> >  > 			wait_on_page_writeback(page);
> >  > 
> >  > 		if (page->mapping == mapping && !PageWriteback(page) &&
> >  > 					test_clear_page_dirty(page)) {
> >  > 
> >  > 
> >  > then I don't see the race - the page lock synchronises the two threads?
> >  > 
> > 
> >  But filemap_fdatawait does not look at the page lock. So there's a
> >  tiny window when the page is on locked_pages with PG_dirty cleared
> >  and PG_writeback not set.
> 
> OK, but the thread which is running fdatawrite/fdatawait isn't interested
> in that page, because it must have been dirtied _after_ this thread has
> passed through filemap_fdatawrite(), yes?

Not exactly. The page could actually have been dirtied _before_ this 
thread passes through filemap_datawrite, but is just being parallely 
written back by a background thread.

Regards
Suparna

> 
> Which is desired behaviour for fsync(), but perhaps not suitable when this
> code is reused for the O_DIRECT pagecache synchronisation function.
> 

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India


  reply	other threads:[~2003-12-31 10:04 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <3FCD4B66.8090905@us.ibm.com>
2003-12-06  1:29 ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Daniel McNeil
2003-12-08 18:23   ` Daniel McNeil
2003-12-12  0:51     ` Daniel McNeil
2003-12-17  1:25       ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Daniel McNeil
2003-12-17  2:03         ` Andrew Morton
2003-12-17 19:25           ` Daniel McNeil
2003-12-17 20:17             ` Janet Morgan
2003-12-31  9:18           ` Suparna Bhattacharya
2003-12-31  9:35             ` Andrew Morton
2003-12-31  9:55               ` Suparna Bhattacharya
2003-12-31  9:59                 ` Andrew Morton
2003-12-31 10:09                   ` Suparna Bhattacharya [this message]
2003-12-31 10:10                     ` Andrew Morton
2003-12-31 10:48                       ` Suparna Bhattacharya
2003-12-31 10:53                         ` Andrew Morton
2003-12-31 10:54                           ` Andrew Morton
2003-12-31 11:17                             ` Andrew Morton
2003-12-31 22:34                               ` [PATCH linux-2.6.1-rc1-mm1] filemap_fdatawait.patch Daniel McNeil
2003-12-31 22:41                                 ` [PATCH linux-2.6.1-rc1-mm1] aiodio_fallback_bio_count.patch Daniel McNeil
2003-12-31 23:46                                   ` Andrew Morton
2004-01-02  5:14                                     ` Suparna Bhattacharya
2004-01-02  7:46                                       ` Andrew Morton
2004-01-05  3:55                                         ` Suparna Bhattacharya
2004-01-05  5:06                                           ` Andrew Morton
2004-01-05  5:28                                             ` Suparna Bhattacharya
2004-01-05  5:28                                               ` Andrew Morton
2004-01-05  6:06                                                 ` Suparna Bhattacharya
2004-01-05  6:14                                                 ` Lincoln Dale
2003-12-31 22:47                                 ` [PATCH linux-2.6.1-rc1-mm1] dio_isize.patch Daniel McNeil
2003-12-31 23:42                                 ` [PATCH linux-2.6.1-rc1-mm1] filemap_fdatawait.patch Andrew Morton
2004-01-02  4:20                                   ` Suparna Bhattacharya
2004-01-02  4:36                                     ` Andrew Morton
2004-01-02  5:50                               ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Suparna Bhattacharya
2004-01-02  7:31                                 ` Andrew Morton
2004-01-05 13:49                                 ` Marcelo Tosatti
2004-01-05 20:27                                   ` Andrew Morton
2004-03-29 15:44                                 ` Marcelo Tosatti
2004-01-11 23:14                               ` Janet Morgan
2004-01-11 23:44                                 ` Andrew Morton
2004-01-12 18:00                                   ` filemap_fdatawait.patch Daniel McNeil
2004-01-12 19:39                                   ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Janet Morgan
2004-01-12 19:46                                     ` Daniel McNeil
2004-01-13  4:12                                 ` Janet Morgan
2003-12-30  4:53       ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Suparna Bhattacharya
2003-12-31  0:29         ` Daniel McNeil
2003-12-31  6:09           ` Suparna Bhattacharya
2004-01-08 23:55             ` Daniel McNeil
2004-01-09  3:55               ` Suparna Bhattacharya
2004-02-05  1:39                 ` [PATCH 2.6.2-rc3-mm1] DIO read race fix Daniel McNeil
2004-02-05  1:54                   ` Badari Pulavarty
2004-02-05  2:07                   ` Andrew Morton
2004-02-05  2:54                     ` Janet Morgan
2004-02-05  3:19                       ` Andrew Morton
2004-02-05  3:43                         ` Suparna Bhattacharya
2004-02-05  5:33                   ` Andrew Morton
2004-02-05 17:52                     ` Daniel McNeil
2004-02-05 18:53                     ` Badari Pulavarty
2004-03-29 15:41           ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Suparna Bhattacharya

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