New submission from STINNER Victor <vstin...@redhat.com>:
The following test_tarfile tests fail on ppc64 when using tmpfs filesystem
(which is the case on RHEL package build server):
* test_sparse_file_00 (test.test_tarfile.GNUReadTest)
* test_sparse_file_01 (test.test_tarfile.GNUReadTest)
* test_sparse_file_10 (test.test_tarfile.GNUReadTest)
* test_sparse_file_old (test.test_tarfile.GNUReadTest)
Example of failure:
======================================================================
FAIL: test_sparse_file_00 (test.test_tarfile.GNUReadTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/builddir/build/BUILD/Python-3.6.6/Lib/test/test_tarfile.py", line 964,
in test_sparse_file_00
self._test_sparse_file("gnu/sparse-0.0")
File "/builddir/build/BUILD/Python-3.6.6/Lib/test/test_tarfile.py", line 958,
in _test_sparse_file
self.assertLess(s.st_blocks * 512, s.st_size)
AssertionError: 131072 not less than 86016
Bug first report on RHEL8:
https://bugzilla.redhat.com/show_bug.cgi?id=1639490
test_tarfile has _fs_supports_holes() function to check if the filesystem
supports sparse files with holes. The function returns True on:
* ext4 filesystem on x86_64 on my Fedora 29 (kernel 4.19)
* ext4 filesystem on x86_64 on my Fedora 29 (kernel 4.19)
* XFS filesystem on ppc64le (kernel 4.18)
* tmpfs filesystem on ppc64le (kernel 4.18)
In short, it always return True on x86_64 and ppc64le Linux kernels.
Problem: in practice, "tmpfs filesystem on ppc64le (kernel 4.18)" doesn't fully
support sparse files.
--
Example from:
https://bugzilla.redhat.com/show_bug.cgi?id=1639490#c5
# ls -lhs ~/sparse
48K -rw-r--r--. 1 root root 84K Jan 18 05:36 /root/sparse
Copy a sparse file from XFS to tmpfs: cp --sparse=always and fallocate --dig
fail to punch holes, the file always take 128K on disk on tmpfs.
# cp sparse /root/mytmp/sparse --sparse=always
# ls -lhs /root/mytmp/sparse
128K -rw-r--r--. 1 root root 84K Jan 18 06:10 /root/mytmp/sparse
# fallocate --dig /root/mytmp/sparse
# ls -lhs /root/mytmp/sparse
128K -rw-r--r--. 1 root root 84K Jan 18 06:10 /root/mytmp/sparse
Counter example on XFS, source and destionation files use 48K on disk fo 84K of
data:
# cp sparse sparse2 --sparse=always
# ls -lhs sparse*
48K -rw-r--r--. 1 root root 84K Jan 18 05:36 sparse
48K -rw-r--r--. 1 root root 84K Jan 18 06:13 sparse2
--
Attached PR fix the _fs_support_holes() heuristic to return properly False on
tmpfs on ppc64le.
----------
components: Tests
messages: 333956
nosy: vstinner
priority: normal
severity: normal
status: open
title: test_tarfile fails on ppc64le when using tmpfs filesystem
versions: Python 3.7, Python 3.8
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue35772>
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