On Wed 01-02-17 18:46:36, Minchan Kim wrote: > On Wed, Feb 01, 2017 at 08:59:24AM +0100, Michal Hocko wrote: > > On Wed 01-02-17 15:48:21, Minchan Kim wrote: > > > Hi Yisheng, > > > > > > On Tue, Jan 31, 2017 at 09:06:18PM +0800, ysxie@xxxxxxxxxxx wrote: > > > > From: Yisheng Xie <xieyisheng1@xxxxxxxxxx> > > > > > > > > This patch changes the return type of isolate_movable_page() > > > > from bool to int. It will return 0 when isolate movable page > > > > successfully, return -EINVAL when the page is not a non-lru movable > > > > page, and for other cases it will return -EBUSY. > > > > > > > > There is no functional change within this patch but prepare > > > > for later patch. > > > > > > > > Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx> > > > > Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx> > > > > > > Sorry for missing this one you guys were discussing. > > > I don't understand the patch's goal although I read later patches. > > > > The point is that the failed isolation has to propagate error up the > > call chain to the userspace which has initiated the migration. > > > > > isolate_movable_pages returns success/fail so that's why I selected > > > bool rather than int but it seems you guys want to propagate more > > > detailed error to the user so added -EBUSY and -EINVAL. > > > > > > But the question is why isolate_lru_pages doesn't have -EINVAL? > > > > It doesn't have to same as isolate_movable_pages. We should just return > > EBUSY when the page is no longer movable. > > Why isolate_lru_page is okay to return -EBUSY in case of race while > isolate_movable_page should return -EINVAL? > What's the logic in your mind? I totally cannot understand. Let me rephrase. Both should return EBUSY. > > > Secondly, madvise man page should update? > > > > Why? > > man page of madvise doesn't say anything about the error propagation > for soft_offline. OK, EBUSY should be documented. > > > Thirdly, if a driver fail isolation due to -ENOMEM, it should be > > > propagated, too? > > > > Yes > > > > > if we want to propagte detailed error to user, driver's isolate_page > > > function should return right error. > > > > Yes > > It seems we are okay to return just -EBUSY until now but now you try to > return more various error. I don't understand what problem you are > seeing with just -EBUSY. Anyway, if you want to do it, it should be able > to propagate error from driver side. That means it should make rule > what kinds of error driver can return. Please write down it to > Documentation/vm/page_migration and fix zsmalloc/virtio-balloon, too. agreed! -- Michal Hocko SUSE Labs -- 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>
