CIFS: SMB2/SMB3 Copy offload support (refcopy) phase 1

This first patch adds the ability for us to do a server side copy
(ie fast copy offloaded to the server to perform, aka refcopy)

"cp --reflink"

of one file to another located on the same server.  This
is much faster than traditional copy (which requires
reading and writing over the network and extra
memcpys).

This first version is not going to be copy
files larger than about 1MB (to Samba) until I add
support for multiple chunks and for autoconfiguring
the chunksize.

It includes:
1) processing of the ioctl
2) marshalling and sending the SMB2/SMB3 fsctl over the network
3) simple parsing of the response

It does not include yet (these will be in followon patches to come soon):
1) support for multiple chunks
2) support for autoconfiguring and remembering the chunksize
3) Support for the older style copychunk which Samba 4.1 server supports
(because this requires write permission on the target file, which
cp does not give you, apparently per-posix).  This may require
a distinct tool (other than cp) and other ioctl to implement.

Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 6183b1b7550f..b50a129572cd 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -534,9 +534,16 @@ struct create_durable {
 	} Data;
 } __packed;
 
+#define COPY_CHUNK_RES_KEY_SIZE	24
+struct resume_key_req {
+	char ResumeKey[COPY_CHUNK_RES_KEY_SIZE];
+	__le32	ContextLength;	/* MBZ */
+	char	Context[0];	/* ignored, Windows sets to 4 bytes of zero */
+} __packed;
+
 /* this goes in the ioctl buffer when doing a copychunk request */
 struct copychunk_ioctl {
-	char SourceKey[24];
+	char SourceKey[COPY_CHUNK_RES_KEY_SIZE];
 	__le32 ChunkCount; /* we are only sending 1 */
 	__le32 Reserved;
 	/* array will only be one chunk long for us */
@@ -546,6 +553,12 @@ struct copychunk_ioctl {
 	__u32 Reserved2;
 } __packed;
 
+struct copychunk_ioctl_rsp {
+	__le32 ChunksWritten;
+	__le32 ChunkBytesWritten;
+	__le32 TotalBytesWritten;
+} __packed;
+
 /* Response and Request are the same format */
 struct validate_negotiate_info {
 	__le32 Capabilities;