Hi Anshuman, On Fri, Nov 09, 2018 at 03:50:41PM +0530, Anshuman Khandual wrote: > > > On 11/09/2018 12:17 PM, Naoya Horiguchi wrote: > > set_hwpoison_free_buddy_page() could fail, then the target page is > > finally not isolated, so it's better to report -EBUSY for userspace > > to know the failure and chance of retry. > > > > IIUC set_hwpoison_free_buddy_page() could only fail if the page is not > free in the buddy. At least for soft_offline_huge_page() that wont be > the case otherwise dissolve_free_huge_page() would have returned non > zero -EBUSY. Is there any other reason set_hwpoison_free_buddy_page() > would not succeed ? There is a race window between page freeing (after successful soft-offline -> page migration case) and the containment by set_hwpoison_free_buddy_page(). Or a target page can be allocated just after get_any_page() decided that the target page is a free page. So set_hwpoison_free_buddy_page() would safely fail in such cases. Thanks, Naoya Horiguchi > > > And for consistency, this patch moves set_hwpoison_free_buddy_page() > > in unmap_and_move() to __soft_offline_page(). > > Yeah this check should be handled in soft offline functions not inside > migrations they trigger. >
