cifs: add FALLOC_FL_INSERT_RANGE support

Emulated via server side copy and setsize for
SMB3 and later. In the future we could compound
this (and/or optionally use DUPLICATE_EXTENTS
if supported by the server).
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -3721,6 +3721,44 @@ static long smb3_collapse_range(struct file *file, struct cifs_tcon *tcon,
 	return rc;
 }
 
+static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
+			      loff_t off, loff_t len)
+{
+	int rc;
+	unsigned int xid;
+	struct cifsFileInfo *cfile = file->private_data;
+	__le64 eof;
+	__u64  count;
+
+	xid = get_xid();
+
+	if (off >= i_size_read(file->f_inode)) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	count = i_size_read(file->f_inode) - off;
+	eof = cpu_to_le64(i_size_read(file->f_inode) + len);
+
+	rc = SMB2_set_eof(xid, tcon, cfile->fid.persistent_fid,
+			  cfile->fid.volatile_fid, cfile->pid, &eof);
+	if (rc < 0)
+		goto out;
+
+	rc = smb2_copychunk_range(xid, cfile, cfile, off, count, off + len);
+	if (rc < 0)
+		goto out;
+
+	rc = smb3_zero_range(file, tcon, off, len, 1);
+	if (rc < 0)
+		goto out;
+
+	rc = 0;
+ out:
+	free_xid(xid);
+	return rc;
+}
+
 static loff_t smb3_llseek(struct file *file, struct cifs_tcon *tcon, loff_t offset, int whence)
 {
 	struct cifsFileInfo *wrcfile, *cfile = file->private_data;
@@ -3894,6 +3932,8 @@ static long smb3_fallocate(struct file *file, struct cifs_tcon *tcon, int mode,
 		return smb3_simple_falloc(file, tcon, off, len, true);
 	else if (mode == FALLOC_FL_COLLAPSE_RANGE)
 		return smb3_collapse_range(file, tcon, off, len);
+	else if (mode == FALLOC_FL_INSERT_RANGE)
+		return smb3_insert_range(file, tcon, off, len);
 	else if (mode == 0)
 		return smb3_simple_falloc(file, tcon, off, len, false);