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net: add get_netmem/put_netmem support

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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: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-3-almasrymina@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Mina Almasry
2025-05-08 00:48:22 +00:00
committed by Paolo Abeni
parent 03e96b8c11
commit e9f3d61db5
5 changed files with 65 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
net/core/devmem.h
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@@ -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)
{