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, 82 insertions, 0 deletions

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c571be8..11dde4b 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -494,6 +494,85 @@ smb2_close_file(const unsigned int xid, struct cifs_tcon *tcon,
 }
 
 static int
+SMB2_request_res_key(const unsigned int xid, struct cifs_tcon *tcon,
+		     u64 persistent_fid, u64 volatile_fid,
+		     struct copychunk_ioctl *pcchunk)
+{
+	int rc;
+	unsigned int ret_data_len;
+	struct resume_key_req *res_key;
+
+	rc = SMB2_ioctl(xid, tcon, persistent_fid, volatile_fid,
+			FSCTL_SRV_REQUEST_RESUME_KEY, true /* is_fsctl */,
+			NULL, 0 /* no input */,
+			(char **)&res_key, &ret_data_len);
+
+	if (rc) {
+		cifs_dbg(VFS, "refcpy ioctl error %d getting resume key\n", rc);
+		goto req_res_key_exit;
+	}
+	if (ret_data_len < sizeof(struct resume_key_req)) {
+		cifs_dbg(VFS, "Invalid refcopy resume key length\n");
+		rc = -EINVAL;
+		goto req_res_key_exit;
+	}
+	memcpy(pcchunk->SourceKey, res_key->ResumeKey, COPY_CHUNK_RES_KEY_SIZE);
+
+req_res_key_exit:
+	kfree(res_key);
+	return rc;
+}
+
+static int
+smb2_clone_range(const unsigned int xid,
+			struct cifsFileInfo *srcfile,
+			struct cifsFileInfo *trgtfile, u64 src_off,
+			u64 len, u64 dest_off)
+{
+	int rc;
+	unsigned int ret_data_len;
+	struct copychunk_ioctl *pcchunk;
+	char *retbuf = NULL;
+
+	pcchunk = kmalloc(sizeof(struct copychunk_ioctl), GFP_KERNEL);
+
+	if (pcchunk == NULL)
+		return -ENOMEM;
+
+	cifs_dbg(FYI, "in smb2_clone_range - about to call request res key\n");
+	/* Request a key from the server to identify the source of the copy */
+	rc = SMB2_request_res_key(xid, tlink_tcon(srcfile->tlink),
+				srcfile->fid.persistent_fid,
+				srcfile->fid.volatile_fid, pcchunk);
+
+	/* Note: request_res_key sets res_key null only if rc !=0 */
+	if (rc)
+		return rc;
+
+	/* For now array only one chunk long, will make more flexible later */
+	pcchunk->ChunkCount = __constant_cpu_to_le32(1);
+	pcchunk->Reserved = 0;
+	pcchunk->SourceOffset = cpu_to_le64(src_off);
+	pcchunk->TargetOffset = cpu_to_le64(dest_off);
+	pcchunk->Length = cpu_to_le32(len);
+	pcchunk->Reserved2 = 0;
+
+	/* Request that server copy to target from src file identified by key */
+	rc = SMB2_ioctl(xid, tlink_tcon(trgtfile->tlink),
+			trgtfile->fid.persistent_fid,
+			trgtfile->fid.volatile_fid, FSCTL_SRV_COPYCHUNK_WRITE,
+			true /* is_fsctl */, (char *)pcchunk,
+			sizeof(struct copychunk_ioctl),	&retbuf, &ret_data_len);
+
+	/* BB need to special case rc = EINVAL to alter chunk size */
+
+	cifs_dbg(FYI, "rc %d data length out %d\n", rc, ret_data_len);
+
+	kfree(pcchunk);
+	return rc;
+}
+
+static int
 smb2_flush_file(const unsigned int xid, struct cifs_tcon *tcon,
 		struct cifs_fid *fid)
 {
@@ -1017,6 +1096,7 @@ struct smb_version_operations smb20_operations = {
 	.set_oplock_level = smb2_set_oplock_level,
 	.create_lease_buf = smb2_create_lease_buf,
 	.parse_lease_buf = smb2_parse_lease_buf,
+	.clone_range = smb2_clone_range,
 };
 
 struct smb_version_operations smb21_operations = {
@@ -1090,6 +1170,7 @@ struct smb_version_operations smb21_operations = {
 	.set_oplock_level = smb21_set_oplock_level,
 	.create_lease_buf = smb2_create_lease_buf,
 	.parse_lease_buf = smb2_parse_lease_buf,
+	.clone_range = smb2_clone_range,
 };
 
 struct smb_version_operations smb30_operations = {
@@ -1165,6 +1246,7 @@ struct smb_version_operations smb30_operations = {
 	.set_oplock_level = smb3_set_oplock_level,
 	.create_lease_buf = smb3_create_lease_buf,
 	.parse_lease_buf = smb3_parse_lease_buf,
+	.clone_range = smb2_clone_range,
 };
 
 struct smb_version_values smb20_values = {