On 11/20/2013 03:24 PM, Daniel Vetter wrote: > On Wed, Nov 20, 2013 at 01:55:49AM -0800, Thomas Hellstrom wrote: >> Not sure if there are any user-space users of private bo mappings, but >> if there are, or will be, zapping the COW'd pages when, for example, >> moving a bo would confuse the user immensely since the net effect for the >> user would be that pages written to would lose their contents. >> >> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com> > Presuming I'm not horribly confused about that all the vm slang in the > kerneldoc means this changes is > > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> > > Now I still hold that userspace creating anynomous bo mappings is rather > crazy, but meh ;-) I guess the real question is whether we have anyone > relying on this out there (or planing to), in which case we either need to > funnel this through stable kernels or whack a drm feature flag onto > drivers/kernels with this fixed. But I seriously hope the answer is no. > > Cheers, Daniel > Thanks for reviewing. I don't think there's a need to take this through stable, since I don't know of anyone using private VMAs,
Actually I'll need to hold off on this for a while since on some archs this may cause ptes of shared pages to not be zapped. If the arch doesn't have PTE_SPECIAL, shared pages on MIXEDMAP vmas will come through as vm_normal_page, and since page->mapping is usually (un)set to NULL by our drivers, this will result in false positives for COW'ed pages. So that test is buggy, or us not setting page->mapping to the mapping we use is buggy. It's too late in the day to decide which. /Thomas
