Be more selective about file metdata in listdir

The directory iterator we use is configurable about what file
metdata to retrieve. This can in some situations significantly
improve performance of generating directory listing.

src/middlewared/middlewared/plugins/filesystem.py

@@ -20,7 +20,7 @@
 from middlewared.utils.filesystem import attrs, stat_x
 from middlewared.utils.filesystem.acl import acl_is_present
 from middlewared.utils.filesystem.constants import FileType
-from middlewared.utils.filesystem.directory import DirectoryIterator
+from middlewared.utils.filesystem.directory import DirectoryIterator, DirectoryRequestMask
 from middlewared.utils.filesystem.utils import timespec_convert
 from middlewared.utils.mount import getmntinfo
 from middlewared.utils.nss import pwd, grp
@@ -214,6 +214,31 @@ def mkdir(self, data):
             'zfs_attrs': ['ARCHIVE']
         }
 
+    @private
+    def listdir_request_mask(self, select):
+        """ create request mask for directory listing """
+        if select is None:
+            # request_mask=None means ALL in the directory iterator
+            return None
+
+        request_mask = 0
+        for i in select:
+            selected = i[0] if isinstance(i, list) else i
+
+            match selected:
+                case 'realpath':
+                    request_mask |= DirectoryRequestMask.REALPATH
+                case 'acl':
+                    request_mask |= DirectoryRequestMask.ACL
+                case 'zfs_attrs':
+                    request_mask |= DirectoryRequestMask.ZFS_ATTRS
+                case 'is_ctldir':
+                    request_mask |= DirectoryRequestMask.CTLDIR
+                case 'xattrs':
+                    request_mask |= DirectoryRequestMask.XATTRS
+
+        return request_mask
+
     @accepts(
         Str('path', required=True),
         Ref('query-filters'),
@@ -274,6 +299,19 @@ def listdir(self, path, filters, options):
         if not path.is_dir():
             raise CallError(f'Path {path} is not a directory', errno.ENOTDIR)
 
+        if options.get('count') is True:
+            # We're just getting count, drop any unnecessary info
+            request_mask = 0
+        else:
+            request_mask = self.listdir_request_mask(options.get('select', None))
+
+        if request_mask and (request_mask & DirectoryRequestMask.ZFS_ATTRS):
+            # Make sure this is actually ZFS before issuing FS ioctls
+            try:
+                self.get_zfs_attributes(path)
+            except Exception:
+                raise CallError(f'{path}: ZFS attributes are not supported.')
+
         file_type = None
         for filter_ in filters:
             if filter_[0] not in ['type']:
@@ -300,7 +338,7 @@ def listdir(self, path, filters, options):
             # filter these here.
             filters.extend([['is_mountpoint', '=', True], ['name', '!=', IX_APPS_DIR_NAME]])
 
-        with DirectoryIterator(path, file_type=file_type) as d_iter:
+        with DirectoryIterator(path, file_type=file_type, request_mask=request_mask) as d_iter:
             return filter_list(d_iter, filters, options)
 
     @accepts(Str('path'), roles=['FILESYSTEM_ATTRS_READ'])