linux-kernel - Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped files

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Date:	Fri, 18 Jan 2008 10:43:35 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Miklos Szeredi <miklos@...redi.hu>
cc:	peterz@...radead.org, salikhmetov@...il.com, linux-mm@...ck.org,
	jakob@...hought.net, linux-kernel@...r.kernel.org,
	valdis.kletnieks@...edu, riel@...hat.com, ksm@...dk,
	staubach@...hat.com, jesper.juhl@...il.com,
	akpm@...ux-foundation.org, protasnb@...il.com,
	r.e.wolff@...wizard.nl, hidave.darkstar@...il.com,
	hch@...radead.org
Subject: Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped
 files



On Fri, 18 Jan 2008, Miklos Szeredi wrote:
> 
> That would need a new page flag (PG_mmap_dirty?).  Do we have one
> available?

Yeah, that would be bad. We probably have flags free, but those page flags 
are always a pain. Scratch that.

How about just setting a per-vma dirty flag, and then instead of updating 
the mtime when taking the dirty-page fault, we just set that flag?

Then, on unmap and msync, we just do

	if (vma->dirty-flag) {
		vma->dirty_flag = 0;
		update_file_times(vma->vm_file);
	}

and be done with it? 
		

			Linus
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