Fix SMB311 posix special file creation to servers which do not advertise reparse support

JIRA: https://issues.redhat.com/browse/RHEL-104401

commit 8767cb3
Author: Steve French <stfrench@microsoft.com>
Date:   Mon Jul 14 22:16:19 2025 -0500

    Fix SMB311 posix special file creation to servers which do not advertise reparse support
    
    Some servers (including Samba), support the SMB3.1.1 POSIX Extensions (which use reparse
    points for handling special files) but do not properly advertise file system attribute
    FILE_SUPPORTS_REPARSE_POINTS.  Although we don't check for this attribute flag when
    querying special file information, we do check it when creating special files which
    causes them to fail unnecessarily.   If we have negotiated SMB3.1.1 POSIX Extensions
    with the server we can expect the server to support creating special files via
    reparse points, and even if the server fails the operation due to really forbidding
    creating special files, then it should be no problem and is more likely to return a
    more accurate rc in any case (e.g. EACCES instead of EOPNOTSUPP).
    
    Allow creating special files as long as the server supports either reparse points
    or the SMB3.1.1 POSIX Extensions (note that if the "sfu" mount option is specified
    it uses a different way of storing special files that does not rely on reparse points).
    
    Cc: <stable@vger.kernel.org>
    Fixes: 6c06be9 ("cifs: Check if server supports reparse points before using them")
    Acked-by: Ralph Boehme <slow@samba.org>
    Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
    Signed-off-by: Steve French <stfrench@microsoft.com>

Signed-off-by: Paulo Alcantara <paalcant@redhat.com>

Author: pcacjr

fs/smb/client/smb2inode.c

@@ -1346,7 +1346,8 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
 	 * empty object on the server.
 	 */
 	if (!(le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS))
-		return ERR_PTR(-EOPNOTSUPP);
+		if (!tcon->posix_extensions)
+			return ERR_PTR(-EOPNOTSUPP);
 
 	oparms = CIFS_OPARMS(cifs_sb, tcon, full_path,
 			     SYNCHRONIZE | DELETE |

fs/smb/client/smb2ops.c

@@ -5195,7 +5195,8 @@ static int smb2_make_node(unsigned int xid, struct inode *inode,
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL) {
 		rc = cifs_sfu_make_node(xid, inode, dentry, tcon,
 					full_path, mode, dev);
-	} else if (le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS) {
+	} else if ((le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS)
+		|| (tcon->posix_extensions)) {
 		rc = smb2_mknod_reparse(xid, inode, dentry, tcon,
 					full_path, mode, dev);
 	}