Merge pull request #1464 from ThomasWaldmann/fix-xattr-exception

xattr: dynamically grow result buffer until it fits, fixes #1462

borg/testsuite/xattr.py

@@ -2,7 +2,7 @@
 import tempfile
 import unittest
 
-from ..xattr import is_enabled, getxattr, setxattr, listxattr
+from ..xattr import is_enabled, getxattr, setxattr, listxattr, get_buffer
 from . import BaseTestCase
 
 
@@ -38,3 +38,23 @@ def test(self):
         self.assert_equal(getxattr(self.tmpfile.fileno(), 'user.foo'), b'bar')
         self.assert_equal(getxattr(self.symlink, 'user.foo'), b'bar')
         self.assert_equal(getxattr(self.tmpfile.name, 'user.empty'), None)
+
+    def test_listxattr_buffer_growth(self):
+        # make it work even with ext4, which imposes rather low limits
+        get_buffer(size=64, init=True)
+        # xattr raw key list will be size 9 * (10 + 1), which is > 64
+        keys = ['user.attr%d' % i for i in range(9)]
+        for key in keys:
+            setxattr(self.tmpfile.name, key, b'x')
+        got_keys = listxattr(self.tmpfile.name)
+        self.assert_equal_se(got_keys, keys)
+        self.assert_equal(len(get_buffer()), 128)
+
+    def test_getxattr_buffer_growth(self):
+        # make it work even with ext4, which imposes rather low limits
+        get_buffer(size=64, init=True)
+        value = b'x' * 126
+        setxattr(self.tmpfile.name, 'user.big', value)
+        got_value = getxattr(self.tmpfile.name, 'user.big')
+        self.assert_equal(value, got_value)
+        self.assert_equal(len(get_buffer()), 128)