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From: Miklos Szeredi <miklos@szeredi.hu>
To: staubach@redhat.com
Cc: miklos@szeredi.hu, akpm@linux-foundation.org,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [patch 01/22] update ctime and mtime for mmaped write
Date: Thu, 01 Mar 2007 08:25:12 +0100	[thread overview]
Message-ID: <E1HMff6-0001es-00@dorka.pomaz.szeredi.hu> (raw)
In-Reply-To: <45E5EF89.4050707@redhat.com> (message from Peter Staubach on Wed, 28 Feb 2007 16:09:29 -0500)

> >> What happens if the application overwrites what it had written some
> >> time later?  Nothing.  The page is already read-write, the pte dirty,
> >> so even though the file was clearly modified, there's absolutely no
> >> way in which this can be used to force an update to the timestamp.
> >>     
> >
> > Which, I realize now, actually means, that the patch is wrong.  Msync
> > will have to write protect the page table entries, so that later
> > dirtyings may have an effect on the timestamp.
> 
> I thought that PeterZ's changes were to write-protect the page after
> cleaning it so that future modifications could be detected and tracked
> accordingly?  Does the right thing not happen already?

Yes, but MS_ASYNC does not clean the pages.

In fact a better solution may be to rely on the dirty bit in the page
tables, so that no more page faults are necessary.

Thanks,
Miklos

  reply	other threads:[~2007-03-01  7:25 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-27 23:14 [patch 00/22] misc VFS/VM patches and fuse writable shared mapping support Miklos Szeredi
2007-02-27 23:14 ` [patch 01/22] update ctime and mtime for mmaped write Miklos Szeredi
2007-02-28 14:16   ` Peter Staubach
2007-02-28 17:06     ` Miklos Szeredi
2007-02-28 17:21       ` Peter Staubach
2007-02-28 17:51         ` Miklos Szeredi
2007-02-28 20:01           ` Peter Staubach
2007-02-28 20:35             ` Miklos Szeredi
2007-02-28 20:58               ` Miklos Szeredi
2007-02-28 21:09                 ` Peter Staubach
2007-03-01  7:25                   ` Miklos Szeredi [this message]
2007-02-27 23:14 ` [patch 02/22] fix quadratic behavior of shrink_dcache_parent() Miklos Szeredi
2007-02-27 23:14 ` [patch 03/22] fix deadlock in balance_dirty_pages Miklos Szeredi
2007-02-27 23:14 ` [patch 04/22] fix deadlock in throttle_vm_writeout Miklos Szeredi
2007-02-27 23:14 ` [patch 05/22] balance dirty pages from loop device Miklos Szeredi
2007-02-27 23:14 ` [patch 06/22] consolidate generic_writepages and mpage_writepages Miklos Szeredi
2007-02-27 23:14 ` [patch 07/22] add filesystem subtype support Miklos Szeredi
2007-02-27 23:14 ` [patch 08/22] fuse: update backing_dev_info congestion state Miklos Szeredi
2007-02-27 23:14 ` [patch 09/22] fuse: fix reserved request wake up Miklos Szeredi
2007-02-27 23:14 ` [patch 10/22] fuse: add reference counting to fuse_file Miklos Szeredi
2007-02-27 23:14 ` [patch 11/22] fuse: add truncation semaphore Miklos Szeredi
2007-02-27 23:14 ` [patch 12/22] fuse: fix page invalidation Miklos Szeredi
2007-02-27 23:14 ` [patch 13/22] fuse: add list of writable files to fuse_inode Miklos Szeredi
2007-02-27 23:14 ` [patch 14/22] fuse: add helper for asynchronous writes Miklos Szeredi
2007-02-27 23:14 ` [patch 15/22] add non-owner variant of down_read_trylock() Miklos Szeredi
2007-02-27 23:14 ` [patch 16/22] fuse: add fuse_writepage() function Miklos Szeredi
2007-02-27 23:14 ` [patch 17/22] fuse: writable shared mmap support Miklos Szeredi
2007-02-27 23:15 ` [patch 18/22] fuse: add fuse_writepages() function Miklos Szeredi
2007-02-27 23:15 ` [patch 19/22] export sync_sb() to modules Miklos Szeredi
2007-02-27 23:15 ` [patch 20/22] fuse: make dirty stats available Miklos Szeredi
2007-02-27 23:15 ` [patch 21/22] fuse: limit dirty pages Miklos Szeredi
2007-02-27 23:15 ` [patch 22/22] fuse: allow big write requests Miklos Szeredi

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