Commit e9f3d61d authored by Mina Almasry's avatar Mina Almasry Committed by Paolo Abeni
Browse files

net: add get_netmem/put_netmem support 



Currently net_iovs support only pp ref counts, and do not support a
page ref equivalent.

This is fine for the RX path as net_iovs are used exclusively with the
pp and only pp refcounting is needed there. The TX path however does not
use pp ref counts, thus, support for get_page/put_page equivalent is
needed for netmem.

Support get_netmem/put_netmem. Check the type of the netmem before
passing it to page or net_iov specific code to obtain a page ref
equivalent.

For dmabuf net_iovs, we obtain a ref on the underlying binding. This
ensures the entire binding doesn't disappear until all the net_iovs have
been put_netmem'ed. We do not need to track the refcount of individual
dmabuf net_iovs as we don't allocate/free them from a pool similar to
what the buddy allocator does for pages.

This code is written to be extensible by other net_iov implementers.
get_netmem/put_netmem will check the type of the netmem and route it to
the correct helper:

pages -> [get|put]_page()
dmabuf net_iovs -> net_devmem_[get|put]_net_iov()
new net_iovs ->	new helpers

Signed-off-by: default avatarMina Almasry <almasrymina@google.com>
Acked-by: default avatarStanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-3-almasrymina@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 03e96b8c

include/linux/skbuff_ref.h

+2 −2
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ 
 */

static inline void __skb_frag_ref(skb_frag_t *frag)

{

	get_page(skb_frag_page(frag));

	get_netmem(skb_frag_netmem(frag));

}



/**
@@ -40,7 +40,7 @@ static inline void skb_page_unref(netmem_ref netmem, bool recycle) 
	if (recycle && napi_pp_put_page(netmem))

		return;

#endif

	put_page(netmem_to_page(netmem));

	put_netmem(netmem);

}



/**

include/net/netmem.h

+3 −0
Original line number Diff line number Diff line
@@ -273,4 +273,7 @@ static inline unsigned long netmem_get_dma_addr(netmem_ref netmem) 
	return __netmem_clear_lsb(netmem)->dma_addr;

}



void get_netmem(netmem_ref netmem);

void put_netmem(netmem_ref netmem);



#endif /* _NET_NETMEM_H */

net/core/devmem.c

+10 −0
Original line number Diff line number Diff line
@@ -295,6 +295,16 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd, 
	return ERR_PTR(err);

}



void net_devmem_get_net_iov(struct net_iov *niov)

{

	net_devmem_dmabuf_binding_get(net_devmem_iov_binding(niov));

}



void net_devmem_put_net_iov(struct net_iov *niov)

{

	net_devmem_dmabuf_binding_put(net_devmem_iov_binding(niov));

}



/*** "Dmabuf devmem memory provider" ***/



int mp_dmabuf_devmem_init(struct page_pool *pool)

net/core/devmem.h

+20 −0
Original line number Diff line number Diff line
@@ -29,6 +29,10 @@ struct net_devmem_dmabuf_binding { 
	 * The binding undos itself and unmaps the underlying dmabuf once all

	 * those refs are dropped and the binding is no longer desired or in

	 * use.

	 *

	 * net_devmem_get_net_iov() on dmabuf net_iovs will increment this

	 * reference, making sure that the binding remains alive until all the

	 * net_iovs are no longer used.

	 */

	refcount_t ref;
@@ -111,6 +115,9 @@ net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding) 
	__net_devmem_dmabuf_binding_free(binding);

}



void net_devmem_get_net_iov(struct net_iov *niov);

void net_devmem_put_net_iov(struct net_iov *niov);



struct net_iov *

net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);

void net_devmem_free_dmabuf(struct net_iov *ppiov);
@@ -120,6 +127,19 @@ bool net_is_devmem_iov(struct net_iov *niov); 
#else

struct net_devmem_dmabuf_binding;



static inline void

net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)

{

}



static inline void net_devmem_get_net_iov(struct net_iov *niov)

{

}



static inline void net_devmem_put_net_iov(struct net_iov *niov)

{

}



static inline void

__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)

{

net/core/skbuff.c

+30 −0
Original line number Diff line number Diff line
@@ -89,6 +89,7 @@ 
#include <linux/textsearch.h>



#include "dev.h"

#include "devmem.h"

#include "netmem_priv.h"

#include "sock_destructor.h"
@@ -7313,3 +7314,32 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, 
	return false;

}

EXPORT_SYMBOL(csum_and_copy_from_iter_full);



void get_netmem(netmem_ref netmem)

{

	struct net_iov *niov;



	if (netmem_is_net_iov(netmem)) {

		niov = netmem_to_net_iov(netmem);

		if (net_is_devmem_iov(niov))

			net_devmem_get_net_iov(netmem_to_net_iov(netmem));

		return;

	}

	get_page(netmem_to_page(netmem));

}

EXPORT_SYMBOL(get_netmem);



void put_netmem(netmem_ref netmem)

{

	struct net_iov *niov;



	if (netmem_is_net_iov(netmem)) {

		niov = netmem_to_net_iov(netmem);

		if (net_is_devmem_iov(niov))

			net_devmem_put_net_iov(netmem_to_net_iov(netmem));

		return;

	}



	put_page(netmem_to_page(netmem));

}

EXPORT_SYMBOL(put_netmem);