linux-kernel - Re: [PATCH] update ctime and mtime for mmaped write

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Message-Id: <E1HJwXe-0003bD-00@dorka.pomaz.szeredi.hu>
Date:	Wed, 21 Feb 2007 19:50:14 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	trond.myklebust@....uio.no
CC:	akpm@...ux-foundation.org, staubach@...hat.com, hugh@...itas.com,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] update ctime and mtime for mmaped write

> > > > This flag is checked in msync() and __fput(), and if set, the file
> > > > times are updated and the flag is cleared
> > > 
> > > Why not also check inside vfs_getattr?
> > 
> > This is the minimum, that the standard asks for.
> > 
> > Note, your porposal would touch the times in vfs_getattr(), which
> > means, that the modification times would depend on the time of the
> > last stat() call, which is not really right, though it would still be
> > conforming.
> > 
> > It is much saner, if the modification time is always the time of the
> > last write() or msync().
> 
> I disagree. The above doesn't allow a program like 'make' to discover
> whether or not the file has changed by simply calling stat(). Instead,
> you're forcing a call to msync()+stat().

Yes, but that's the only portable way _anyway_.

And it probably doesn't matter, programs using mmap to write to a file
_will_ call msync, or at least close the file, when they're done.

Thanks,
Miklos
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