On Thu, 9 Apr 2015, Susheel Khiani wrote: > Hi, > > We are seeing an issue during try_to_unmap_ksm where in call to > try_to_unmap_one is failing. > > try_to_unmap_ksm in this particular case is trying to go through vmas > associated with each rmap_item->anon_vma. What we see is this that the > corresponding page is not mapped to any of the vmas associated with 2 > rmap_item. > > The associated rmap_item in this case looks like pointing to some valid vma > but the said page is not found to be mapped under it. try_to_unmap_one thus > fails to find valid ptes for these vmas. > > At the same time we can see that the page actually is mapped in 2 separate > and different vmas which are not part of rmap_item associated with page. > > So whether rmap_item is pointing to some stale vmas and now the mapping has > changed? Or there is something else going on here. > p > Any pointer would be appreciated. I expected to be able to argue this away, but no: I think you've found a bug, and I think I get it too. I have no idea what's wrong at this point, will set aside some time to investigate, and report back. Which kernel are you using? try_to_unmap_ksm says v3.13 or earlier. Probably doesn't affect the bug, but may affect the patch you'll need. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>