Re: [RFC mm v4 1/2] page_pool: check if nmdesc->pp is !NULL to confirm its usage as pp for net_iov

->pp_magic field in struct page is current used to identify if a page
belongs to a page pool.  However, ->pp_magic will be removed and page
type bit in struct page e.g. PGTY_netpp should be used for that purpose.

As a preparation, the check for net_iov, that is not page-backed, should
avoid using ->pp_magic since net_iov doens't have to do with page type.
Instead, nmdesc->pp can be used if a net_iov or its nmdesc belongs to a
page pool, by making sure nmdesc->pp is NULL otherwise.

For page-backed netmem, just leave unchanged as is, while for net_iov,
make sure nmdesc->pp is initialized to NULL and use nmdesc->pp for the
check.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 net/core/devmem.c      |  1 +
 net/core/netmem_priv.h |  8 ++++++++
 net/core/page_pool.c   | 16 ++++++++++++++--
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/net/core/devmem.c b/net/core/devmem.c
index d9de31a6cc7f..f81b700f1fd1 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c

@@ -291,6 +291,7 @@ net_devmem_bind_dmabuf(struct net_device *dev,
                        niov = &owner->area.niovs[i];
                        niov->type = NET_IOV_DMABUF;
                        niov->owner = &owner->area;
+                       niov->desc.pp = NULL;