On Friday 12 October 2007 20:37, Peter Zijlstra wrote: > On Fri, 2007-10-12 at 02:57 +1000, Nick Piggin wrote: > > On Friday 12 October 2007 19:03, Peter Zijlstra wrote: > > > Subject: mm: avoid dirtying shared mappings on mlock > > > > > > Suleiman noticed that shared mappings get dirtied when mlocked. > > > Avoid this by teaching make_pages_present about this case. > > > > > > Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]> > > > Acked-by: Suleiman Souhlal <[EMAIL PROTECTED]> > > > > Umm, I don't see the other piece of this thread, so I don't > > know what the actual problem was. > > > > But I would really rather not do this. If you do this, then you > > now can get random SIGBUSes when you write into the memory if it > > can't allocate blocks or ... (some other filesystem specific > > condition). > > I'm not getting this, make_pages_present() only has to ensure all the > pages are read from disk and in memory. How is this different from a > read-scan?
I guess because we've mlocked a region that has PROT_WRITE access... but actually, I suppose mlock doesn't technically require that we can write to the memory, only that the page isn't swapped out. Still, it is nice to be able to have a reasonable guarantee of writability. > The pages will still be read-only due to dirty tracking, so the first > write will still do page_mkwrite(). Which can SIGBUS, no? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
