Messages in this thread | | | Date | Tue, 23 Mar 2021 11:40:53 -0400 | From | Peter Xu <> | Subject | Re: [PATCH 02/23] mm: Clear vmf->pte after pte_unmap_same() returns |
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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@redhat.com> > > Good cleanup! Thanks. > Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
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
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