On Tue, Mar 23, 2021 at 10:34:45AM +0800, Miaohe Lin wrote:

Hi:
On 2021/3/23 8:48, Peter Xu wrote:

quoted

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