cifs: Add support for creating SFU symlinks

Linux cifs client can already detect SFU symlinks and reads it content
(target location). But currently is not able to create new symlink. So
implement this missing support.

When 'sfu' mount option is specified and 'mfsymlinks' is not specified then
create new symlinks in SFU-style. This will provide full SFU compatibility
of symlinks when mounting cifs share with 'sfu' option. 'mfsymlinks' option
override SFU for better Apple compatibility as explained in fs_context.c
file in smb3_update_mnt_flags() function.

Extend __cifs_sfu_make_node() function, which now can handle also S_IFLNK
type and refactor structures passed to sync_write() in this function, by
splitting SFU type and SFU data from original combined struct win_dev as
combined fixed-length struct cannot be used for variable-length symlinks.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 62 insertions, 18 deletions

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index a5174bf41e51..11452317b090 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -5055,9 +5055,10 @@ static int smb2_next_header(struct TCP_Server_Info *server, char *buf,
 	return 0;
 }
 
-static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
+int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
 				struct dentry *dentry, struct cifs_tcon *tcon,
-				const char *full_path, umode_t mode, dev_t dev)
+				const char *full_path, umode_t mode, dev_t dev,
+				const char *symname)
 {
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct cifs_open_parms oparms;
@@ -5065,30 +5066,64 @@ static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifs_fid fid;
 	unsigned int bytes_written;
-	struct win_dev pdev = {};
-	struct kvec iov[2];
+	u8 type[8];
+	int type_len = 0;
+	struct {
+		__le64 major;
+		__le64 minor;
+	} __packed pdev = {};
+	__le16 *symname_utf16 = NULL;
+	u8 *data = NULL;
+	int data_len = 0;
+	struct kvec iov[3];
 	__u32 oplock = server->oplocks ? REQ_OPLOCK : 0;
 	int rc;
 
 	switch (mode & S_IFMT) {
 	case S_IFCHR:
-		memcpy(pdev.type, "IntxCHR\0", 8);
+		type_len = 8;
+		memcpy(type, "IntxCHR\0", type_len);
 		pdev.major = cpu_to_le64(MAJOR(dev));
 		pdev.minor = cpu_to_le64(MINOR(dev));
+		data = (u8 *)&pdev;
+		data_len = sizeof(pdev);
 		break;
 	case S_IFBLK:
-		memcpy(pdev.type, "IntxBLK\0", 8);
+		type_len = 8;
+		memcpy(type, "IntxBLK\0", type_len);
 		pdev.major = cpu_to_le64(MAJOR(dev));
 		pdev.minor = cpu_to_le64(MINOR(dev));
+		data = (u8 *)&pdev;
+		data_len = sizeof(pdev);
+		break;
+	case S_IFLNK:
+		type_len = 8;
+		memcpy(type, "IntxLNK\1", type_len);
+		symname_utf16 = cifs_strndup_to_utf16(symname, strlen(symname),
+						      &data_len, cifs_sb->local_nls,
+						      NO_MAP_UNI_RSVD);
+		if (!symname_utf16) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		data_len -= 2; /* symlink is without trailing wide-nul */
+		data = (u8 *)symname_utf16;
 		break;
 	case S_IFSOCK:
-		strscpy(pdev.type, "LnxSOCK");
+		type_len = 8;
+		strscpy(type, "LnxSOCK");
+		data = (u8 *)&pdev;
+		data_len = sizeof(pdev);
 		break;
 	case S_IFIFO:
-		strscpy(pdev.type, "LnxFIFO");
+		type_len = 8;
+		strscpy(type, "LnxFIFO");
+		data = (u8 *)&pdev;
+		data_len = sizeof(pdev);
 		break;
 	default:
-		return -EPERM;
+		rc = -EPERM;
+		goto out;
 	}
 
 	oparms = CIFS_OPARMS(cifs_sb, tcon, full_path, GENERIC_WRITE,
@@ -5098,17 +5133,26 @@ static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
 
 	rc = server->ops->open(xid, &oparms, &oplock, NULL);
 	if (rc)
-		return rc;
+		goto out;
 
-	io_parms.pid = current->tgid;
-	io_parms.tcon = tcon;
-	io_parms.length = sizeof(pdev);
-	iov[1].iov_base = &pdev;
-	iov[1].iov_len = sizeof(pdev);
+	if (type_len + data_len > 0) {
+		io_parms.pid = current->tgid;
+		io_parms.tcon = tcon;
+		io_parms.length = type_len + data_len;
+		iov[1].iov_base = type;
+		iov[1].iov_len = type_len;
+		iov[2].iov_base = data;
+		iov[2].iov_len = data_len;
+
+		rc = server->ops->sync_write(xid, &fid, &io_parms,
+					     &bytes_written,
+					     iov, ARRAY_SIZE(iov)-1);
+	}
 
-	rc = server->ops->sync_write(xid, &fid, &io_parms,
-				     &bytes_written, iov, 1);
 	server->ops->close(xid, tcon, &fid);
+
+out:
+	kfree(symname_utf16);
 	return rc;
 }
 
@@ -5120,7 +5164,7 @@ int cifs_sfu_make_node(unsigned int xid, struct inode *inode,
 	int rc;
 
 	rc = __cifs_sfu_make_node(xid, inode, dentry, tcon,
-				  full_path, mode, dev);
+				  full_path, mode, dev, NULL);
 	if (rc)
 		return rc;