lkml.org 
[lkml]   [2007]   [Mar]   [1]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch 01/22] update ctime and mtime for mmaped write
FromMiklos Szeredi <>
DateThu, 01 Mar 2007 08:25:12 +0100
> >> 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-03-01 08:29    [from the cache]
©2003-2008