1#!/usr/bin/env python3 2# group: rw quick 3# 4# Test cases for the block-status cache. 5# 6# Copyright (C) 2022 Red Hat, Inc. 7# 8# This program is free software; you can redistribute it and/or modify 9# it under the terms of the GNU General Public License as published by 10# the Free Software Foundation; either version 2 of the License, or 11# (at your option) any later version. 12# 13# This program is distributed in the hope that it will be useful, 14# but WITHOUT ANY WARRANTY; without even the implied warranty of 15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16# GNU General Public License for more details. 17# 18# You should have received a copy of the GNU General Public License 19# along with this program. If not, see <http://www.gnu.org/licenses/>. 20# 21 22import os 23import signal 24import iotests 25from iotests import qemu_img_create, qemu_img_map, qemu_nbd 26 27 28image_size = 1 * 1024 * 1024 29test_img = os.path.join(iotests.test_dir, 'test.img') 30 31nbd_pidfile = os.path.join(iotests.test_dir, 'nbd.pid') 32nbd_sock = os.path.join(iotests.sock_dir, 'nbd.sock') 33 34 35class TestBscWithNbd(iotests.QMPTestCase): 36 def setUp(self) -> None: 37 """Just create an empty image with a read-only NBD server on it""" 38 qemu_img_create('-f', iotests.imgfmt, test_img, str(image_size)) 39 40 # Pass --allocation-depth to enable the qemu:allocation-depth context, 41 # which we are going to query to provoke a block-status inquiry with 42 # want_zero=false. 43 assert qemu_nbd(f'--socket={nbd_sock}', 44 f'--format={iotests.imgfmt}', 45 '--persistent', 46 '--allocation-depth', 47 '--read-only', 48 f'--pid-file={nbd_pidfile}', 49 test_img) \ 50 == 0 51 52 def tearDown(self) -> None: 53 with open(nbd_pidfile, encoding='utf-8') as f: 54 pid = int(f.read()) 55 os.kill(pid, signal.SIGTERM) 56 os.remove(nbd_pidfile) 57 os.remove(test_img) 58 59 def test_with_zero_bug(self) -> None: 60 """ 61 Verify that the block-status cache is not corrupted by a 62 want_zero=false call. 63 We can provoke a want_zero=false call with `qemu-img map` over NBD with 64 x-dirty-bitmap=qemu:allocation-depth, so we first run a normal `map` 65 (which results in want_zero=true), then using said 66 qemu:allocation-depth context, and finally another normal `map` to 67 verify that the cache has not been corrupted. 68 """ 69 70 nbd_img_opts = f'driver=nbd,server.type=unix,server.path={nbd_sock}' 71 nbd_img_opts_alloc_depth = nbd_img_opts + \ 72 ',x-dirty-bitmap=qemu:allocation-depth' 73 74 # Normal map, results in want_zero=true. 75 # This will probably detect an allocated data sector first (qemu likes 76 # to allocate the first sector to facilitate alignment probing), and 77 # then the rest to be zero. The BSC will thus contain (if anything) 78 # one range covering the first sector. 79 map_pre = qemu_img_map('--image-opts', nbd_img_opts) 80 81 # qemu:allocation-depth maps for want_zero=false. 82 # want_zero=false should (with the file driver, which the server is 83 # using) report everything as data. While this is sufficient for 84 # want_zero=false, this is nothing that should end up in the 85 # block-status cache. 86 # Due to a bug, this information did end up in the cache, though, and 87 # this would lead to wrong information being returned on subsequent 88 # want_zero=true calls. 89 # 90 # We need to run this map twice: On the first call, we probably still 91 # have the first sector in the cache, and so this will be served from 92 # the cache; and only the subsequent range will be queried from the 93 # block driver. This subsequent range will then be entered into the 94 # cache. 95 # If we did a want_zero=true call at this point, we would thus get 96 # correct information: The first sector is not covered by the cache, so 97 # we would get fresh block-status information from the driver, which 98 # would return a data range, and this would then go into the cache, 99 # evicting the wrong range from the want_zero=false call before. 100 # 101 # Therefore, we need a second want_zero=false map to reproduce: 102 # Since the first sector is not in the cache, the query for its status 103 # will go to the driver, which will return a result that reports the 104 # whole image to be a single data area. This result will then go into 105 # the cache, and so the cache will then report the whole image to 106 # contain data. 107 # 108 # Note that once the cache reports the whole image to contain data, any 109 # subsequent map operation will be served from the cache, and so we can 110 # never loop too many times here. 111 for _ in range(2): 112 # (Ignore the result, this is just to contaminate the cache) 113 qemu_img_map('--image-opts', nbd_img_opts_alloc_depth) 114 115 # Now let's see whether the cache reports everything as data, or 116 # whether we get correct information (i.e. the same as we got on our 117 # first attempt). 118 map_post = qemu_img_map('--image-opts', nbd_img_opts) 119 120 if map_pre != map_post: 121 print('ERROR: Map information differs before and after querying ' + 122 'qemu:allocation-depth') 123 print('Before:') 124 print(map_pre) 125 print('After:') 126 print(map_post) 127 128 self.fail("Map information differs") 129 130 131if __name__ == '__main__': 132 # The block-status cache only works on the protocol layer, so to test it, 133 # we can only use the raw format 134 iotests.main(supported_fmts=['raw'], 135 supported_protocols=['file']) 136