[RFC PATCH 24/36] cifs: Add netmem allocation functions

[David Howells <dhowells@redhat.com>]

Add (stub) functions for doing netmem allocations.  We want to allocate
memory from the netmem buffering as that does bulk DMA and IOMMU
management.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: Tom Talpey <tom@talpey.com>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/smb/client/cifsproto.h |  2 ++
 fs/smb/client/transport.c | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/fs/smb/client/cifsproto.h b/fs/smb/client/cifsproto.h
index 72ee5c5fd8b7..3067056f8ef9 100644
--- a/fs/smb/client/cifsproto.h
+++ b/fs/smb/client/cifsproto.h
@@ -508,5 +508,7 @@ int smb_rxqueue_refill(struct TCP_Server_Info *server, struct netfs_rxqueue *rxq
 		       size_t min_size);
 int smb_rxqueue_consume(struct TCP_Server_Info *server, struct netfs_rxqueue *rxq,
 			size_t amount);
+void *cifs_allocate_tx_buf(struct TCP_Server_Info *server, size_t size);
+void cifs_free_tx_buf(void *p);
 
 #endif			/* _CIFSPROTO_H */
diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index 68536de2c1a0..1599afb9e5cf 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -33,6 +33,26 @@
 #include "smbdirect.h"
 #include "compress.h"
 
+/*
+ * Allocate transmission buffers for a socket.  This memory will be allocated
+ * from the netmem buffers.  It comes with a page ref that we need to drop.
+ * The networking layer can pin it by getting its own ref.
+ */
+void *cifs_allocate_tx_buf(struct TCP_Server_Info *server, size_t size)
+{
+	void *p;
+
+	mutex_lock(&server->tx_alloc_lock);
+	p = page_frag_alloc_align(&server->tx_alloc, size, GFP_NOFS, 8);
+	mutex_unlock(&server->tx_alloc_lock);
+	return p;
+}
+
+void cifs_free_tx_buf(void *p)
+{
+	page_frag_free(p);
+}
+
 struct smb_message *smb_message_alloc(enum smb_command_trace cmd, gfp_t gfp)
 {
 	static atomic_t debug_ids;