Date: Tue, 9 Nov 2004 11:51:22 -0800
From: Andrew Morton <akpm@osdl.org>
To: Andrea Arcangeli <andrea@novell.com>
Cc: shaggy@austin.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] zap_pte_range should not mark non-uptodate pages dirty
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Andrea Arcangeli <andrea@novell.com> wrote:
>
> On Tue, Nov 09, 2004 at 08:15:30AM -0600, Dave Kleikamp wrote:
>  > Andrew & Andrea,
>  > What is the status of this patch?  It would be nice to have it in the
>  > -mm4 kernel.
> 
>  I think we should add an msync in front of O_DIRECT reads too (msync
>  won't hurt other users, and it'll provide full coherency), everything
>  else is ok (the msync can be added as an incremental patch).

I don't think we have a simple way of syncing all ptes which map the pages
without actually shooting those pte's down, via zap_page_range().  A
filemap_sync() will only sync the caller's mm's ptes.

I guess it would be pretty simple to add a sync_but_dont_unmap field to
struct zap_details, and propagate that down.  So we can reuse all the
unmap_vmas() code for an all-mms pte sync.

It could all get very expensive if someone has a bit of the file mapped
though.  Testing is needed there.

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