On Wed, Feb 01, 2017 at 11:00:23AM +0100, Michal Hocko wrote: > 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. It means it's binary return value(success: 0 fail : -EBUSY) so IMO, bool is better and caller should return -EBUSY if that functions returns *false*. No need to make deeper propagation level. Anyway, it's trivial so I'm not against it if you want to make isolate_movable_page returns int. Insetad, please remove -EINVAL in this patch and just return -EBUSY for isolate_movable_page to be consistent with isolate_lru_page. Then, we don't need to fix any driver side, either. Even, no need to update any document because you don't add any new error value. That's enough. -- 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>
