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>

fs/cifs/cifsglob.h

@@ -381,6 +381,9 @@ struct smb_version_operations {
 	char * (*create_lease_buf)(u8 *, u8);
 	/* parse lease context buffer and return oplock/epoch info */
 	__u8 (*parse_lease_buf)(void *, unsigned int *);
+	int (*clone_range)(const unsigned int, struct cifsFileInfo *src_file,
+			struct cifsFileInfo *target_file, u64 src_off, u64 len,
+			u64 dest_off);
 };
 
 struct smb_version_values {

fs/cifs/ioctl.c

@@ -22,12 +22,120 @@
  */
 
 #include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mount.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/btrfs.h>
 #include "cifspdu.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
 #include "cifsfs.h"
 
+static long cifs_ioctl_clone(unsigned int xid, struct file *dst_file,
+			unsigned long srcfd, u64 off, u64 len, u64 destoff)
+{
+	int rc;
+	struct cifsFileInfo *smb_file_target = dst_file->private_data;
+	struct inode *target_inode = file_inode(dst_file);
+	struct cifs_tcon *target_tcon;
+	struct fd src_file;
+	struct cifsFileInfo *smb_file_src;
+	struct inode *src_inode;
+	struct cifs_tcon *src_tcon;
+
+	cifs_dbg(FYI, "ioctl clone range\n");
+	/* the destination must be opened for writing */
+	if (!(dst_file->f_mode & FMODE_WRITE)) {
+		cifs_dbg(FYI, "file target not open for write\n");
+		return -EINVAL;
+	}
+
+	/* check if target volume is readonly and take reference */
+	rc = mnt_want_write_file(dst_file);
+	if (rc) {
+		cifs_dbg(FYI, "mnt_want_write failed with rc %d\n", rc);
+		return rc;
+	}
+
+	src_file = fdget(srcfd);
+	if (!src_file.file) {
+		rc = -EBADF;
+		goto out_drop_write;
+	}
+
+	if ((!src_file.file->private_data) || (!dst_file->private_data)) {
+		rc = -EBADF;
+		cifs_dbg(VFS, "missing cifsFileInfo on copy range src file\n");
+		goto out_fput;
+	}
+
+	rc = -EXDEV;
+	smb_file_target = dst_file->private_data;
+	smb_file_src = src_file.file->private_data;
+	src_tcon = tlink_tcon(smb_file_src->tlink);
+	target_tcon = tlink_tcon(smb_file_target->tlink);
+
+	/* check if source and target are on same tree connection */
+	if (src_tcon != target_tcon) {
+		cifs_dbg(VFS, "file copy src and target on different volume\n");
+		goto out_fput;
+	}
+
+	src_inode = src_file.file->f_dentry->d_inode;
+
+	/*
+	 * Note: cifs case is easier than btrfs since server responsible for
+	 * checks for proper open modes and file type and if it wants
+	 * server could even support copy of range where source = target
+	 */
+
+	/* so we do not deadlock racing two ioctls on same files */
+	if (target_inode < src_inode) {
+		mutex_lock_nested(&target_inode->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_CHILD);
+	} else {
+		mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&target_inode->i_mutex, I_MUTEX_CHILD);
+	}
+
+	/* determine range to clone */
+	rc = -EINVAL;
+	if (off + len > src_inode->i_size || off + len < off)
+		goto out_unlock;
+	if (len == 0)
+		len = src_inode->i_size - off;
+
+	cifs_dbg(FYI, "about to flush pages\n");
+	/* should we flush first and last page first */
+	truncate_inode_pages_range(&target_inode->i_data, destoff,
+				   PAGE_CACHE_ALIGN(destoff + len)-1);
+
+	if (target_tcon->ses->server->ops->clone_range)
+		rc = target_tcon->ses->server->ops->clone_range(xid,
+			smb_file_src, smb_file_target, off, len, destoff);
+
+	/* force revalidate of size and timestamps of target file now
+	   that target is updated on the server */
+	CIFS_I(target_inode)->time = 0;
+out_unlock:
+	/* although unlocking in the reverse order from locking is not
+	   strictly necessary here it is a little cleaner to be consistent */
+	if (target_inode < src_inode) {
+		mutex_unlock(&src_inode->i_mutex);
+		mutex_unlock(&target_inode->i_mutex);
+	} else {
+		mutex_unlock(&target_inode->i_mutex);
+		mutex_unlock(&src_inode->i_mutex);
+	}
+out_fput:
+	fdput(src_file);
+out_drop_write:
+	mnt_drop_write_file(dst_file);
+	return rc;
+}
+
 long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 {
 	struct inode *inode = file_inode(filep);
@@ -105,6 +213,9 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 				cifs_dbg(FYI, "set compress flag rc %d\n", rc);
 			}
 			break;
+		case BTRFS_IOC_CLONE:
+			rc = cifs_ioctl_clone(xid, filep, arg, 0, 0, 0);
+			break;
 		default:
 			cifs_dbg(FYI, "unsupported ioctl\n");
 			break;

fs/cifs/smb2ops.c

@@ -493,6 +493,85 @@ smb2_close_file(const unsigned int xid, struct cifs_tcon *tcon,
 	SMB2_close(xid, tcon, fid->persistent_fid, fid->volatile_fid);
 }
 
+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 = {

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;