On Tue, Mar 23, 2021 at 10:34:45AM +0800, Miaohe Lin wrote: > Hi: > On 2021/3/23 8:48, Peter Xu wrote: > > pte_unmap_same() will always unmap the pte pointer. After the unmap, vmf->pte > > will not be valid any more. We should clear it. > > > > It was safe only because no one is accessing vmf->pte after pte_unmap_same() > > returns, since the only caller of pte_unmap_same() (so far) is do_swap_page(), > > where vmf->pte will in most cases be overwritten very soon. > > > > pte_unmap_same() will be used in other places in follow up patches, so that > > vmf->pte will not always be re-written. This patch enables us to call > > functions like finish_fault() because that'll conditionally unmap the pte by > > checking vmf->pte first. Or, alloc_set_pte() will make sure to allocate a new > > pte even after calling pte_unmap_same(). > > > > Since we'll need to modify vmf->pte, directly pass in vmf into pte_unmap_same() > > and then we can also avoid the long parameter list. > > > > Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> > > Good cleanup! Thanks. > Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Just a note that this is not a pure cleanup - the latter patches may start to depend on the clearing of vmf->pte in their logic. Thanks for the quick review! -- Peter Xu
