CIFS: make mknod() an smb_version_op

This cleanup removes cifs specific code from SMB2/SMB3 code paths
which is cleaner and easier to maintain as the code to handle
special files is improved.  Below is an example creating special files
using 'sfu' mount option over SMB3 to Windows (with this patch)
(Note that to Samba server, support for saving dos attributes
has to be enabled for the SFU mount option to work).

In the future this will also make implementation of creating
special files as reparse points easier (as Windows NFS server does
for example).

   root@smf-Thinkpad-P51:~# stat -c "%F" /mnt2/char
   character special file

   root@smf-Thinkpad-P51:~# stat -c "%F" /mnt2/block
   block special file

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 32dde87feaa9..9a7164c2ea63 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3767,6 +3767,104 @@ smb2_next_header(char *buf)
 	return le32_to_cpu(hdr->NextCommand);
 }
 
+static int
+smb2_make_node(unsigned int xid, struct inode *inode,
+	       struct dentry *dentry, struct cifs_tcon *tcon,
+	       char *full_path, umode_t mode, dev_t dev)
+{
+	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+	int rc = -EPERM;
+	int create_options = CREATE_NOT_DIR | CREATE_OPTION_SPECIAL;
+	FILE_ALL_INFO *buf = NULL;
+	struct cifs_io_parms io_parms;
+	__u32 oplock = 0;
+	struct cifs_fid fid;
+	struct cifs_open_parms oparms;
+	unsigned int bytes_written;
+	struct win_dev *pdev;
+	struct kvec iov[2];
+
+	/*
+	 * Check if mounted with mount parm 'sfu' mount parm.
+	 * SFU emulation should work with all servers, but only
+	 * supports block and char device (no socket & fifo),
+	 * and was used by default in earlier versions of Windows
+	 */
+	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL))
+		goto out;
+
+	/*
+	 * TODO: Add ability to create instead via reparse point. Windows (e.g.
+	 * their current NFS server) uses this approach to expose special files
+	 * over SMB2/SMB3 and Samba will do this with SMB3.1.1 POSIX Extensions
+	 */
+
+	if (!S_ISCHR(mode) && !S_ISBLK(mode))
+		goto out;
+
+	cifs_dbg(FYI, "sfu compat create special file\n");
+
+	buf = kmalloc(sizeof(FILE_ALL_INFO), GFP_KERNEL);
+	if (buf == NULL) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	if (backup_cred(cifs_sb))
+		create_options |= CREATE_OPEN_BACKUP_INTENT;
+
+	oparms.tcon = tcon;
+	oparms.cifs_sb = cifs_sb;
+	oparms.desired_access = GENERIC_WRITE;
+	oparms.create_options = create_options;
+	oparms.disposition = FILE_CREATE;
+	oparms.path = full_path;
+	oparms.fid = &fid;
+	oparms.reconnect = false;
+
+	if (tcon->ses->server->oplocks)
+		oplock = REQ_OPLOCK;
+	else
+		oplock = 0;
+	rc = tcon->ses->server->ops->open(xid, &oparms, &oplock, buf);
+	if (rc)
+		goto out;
+
+	/*
+	 * BB Do not bother to decode buf since no local inode yet to put
+	 * timestamps in, but we can reuse it safely.
+	 */
+
+	pdev = (struct win_dev *)buf;
+	io_parms.pid = current->tgid;
+	io_parms.tcon = tcon;
+	io_parms.offset = 0;
+	io_parms.length = sizeof(struct win_dev);
+	iov[1].iov_base = buf;
+	iov[1].iov_len = sizeof(struct win_dev);
+	if (S_ISCHR(mode)) {
+		memcpy(pdev->type, "IntxCHR", 8);
+		pdev->major = cpu_to_le64(MAJOR(dev));
+		pdev->minor = cpu_to_le64(MINOR(dev));
+		rc = tcon->ses->server->ops->sync_write(xid, &fid, &io_parms,
+							&bytes_written, iov, 1);
+	} else if (S_ISBLK(mode)) {
+		memcpy(pdev->type, "IntxBLK", 8);
+		pdev->major = cpu_to_le64(MAJOR(dev));
+		pdev->minor = cpu_to_le64(MINOR(dev));
+		rc = tcon->ses->server->ops->sync_write(xid, &fid, &io_parms,
+							&bytes_written, iov, 1);
+	}
+	tcon->ses->server->ops->close(xid, tcon, &fid);
+	d_drop(dentry);
+
+	/* FIXME: add code here to set EAs */
+out:
+	kfree(buf);
+	return rc;
+}
+
+
 struct smb_version_operations smb20_operations = {
 	.compare_fids = smb2_compare_fids,
 	.setup_request = smb2_setup_request,
@@ -3861,6 +3959,7 @@ struct smb_version_operations smb20_operations = {
 #endif /* CIFS_ACL */
 	.next_header = smb2_next_header,
 	.ioctl_query_info = smb2_ioctl_query_info,
+	.make_node = smb2_make_node,
 };
 
 struct smb_version_operations smb21_operations = {
@@ -3959,6 +4058,7 @@ struct smb_version_operations smb21_operations = {
 #endif /* CIFS_ACL */
 	.next_header = smb2_next_header,
 	.ioctl_query_info = smb2_ioctl_query_info,
+	.make_node = smb2_make_node,
 };
 
 struct smb_version_operations smb30_operations = {
@@ -4066,6 +4166,7 @@ struct smb_version_operations smb30_operations = {
 #endif /* CIFS_ACL */
 	.next_header = smb2_next_header,
 	.ioctl_query_info = smb2_ioctl_query_info,
+	.make_node = smb2_make_node,
 };
 
 struct smb_version_operations smb311_operations = {
@@ -4174,6 +4275,7 @@ struct smb_version_operations smb311_operations = {
 #endif /* CIFS_ACL */
 	.next_header = smb2_next_header,
 	.ioctl_query_info = smb2_ioctl_query_info,
+	.make_node = smb2_make_node,
 };
 
 struct smb_version_values smb20_values = {