Date:   Fri, 11 Sep 2020 12:41:26 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Dave Chinner <dchinner@...hat.com>,
        Jann Horn <jannh@...gle.com>, Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>,
        Kirill Shutemov <kirill@...temov.name>,
        "Theodore Ts'o" <tytso@....edu>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        Eric Sandeen <sandeen@...hat.com>
Subject: Re: [PATCH 2/2] xfs: don't update mtime on COW faults



On Wed, 9 Sep 2020, Darrick J. Wong wrote:

> On Sat, Sep 05, 2020 at 01:02:33PM -0400, Mikulas Patocka wrote:
> > > > 
> > 
> > I've written this program that tests it - you can integrate it into your 
> > testsuite.
> 
> I don't get it.  You're a filesystem maintainer too, which means you're
> a regular contributor.  Do you:
> 
> (a) not use fstests?  If you don't, I really hope you use something else
> to QA hpfs.

I don't use xfstests on HPFS. I was testing it just by using it. Now I use 
it just a little, but I don't modify it much.

> (b) really think that it's my problem to integrate and submit your
> regression tests for you?
> 
> and (c) what do you want me to do with a piece of code that has no 
> signoff tag, no copyright, and no license?  This is your patch, and 
> therefore your responsibility to develop enough of an appropriate 
> regression test in a proper form that the rest of us can easily 
> determine we have the rights to contribute to it.


If you want a full patch (I copied the script from test 313), I send it 
here.

Mikulas


From: Mikulas Patocka <mpatocka@...hat.com>
Subject: [PATCH] check ctime and mtime vs mmap

Check ctime and mtime are not updated on COW faults
and that they are updated on shared faults

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

---
 src/Makefile          |    3 +-
 src/mmap-timestamp.c  |   53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/generic/609     |   40 +++++++++++++++++++++++++++++++++++++
 tests/generic/609.out |    2 +
 tests/generic/group   |    1 
 5 files changed, 98 insertions(+), 1 deletion(-)

Index: xfstests-dev/src/Makefile
===================================================================
--- xfstests-dev.orig/src/Makefile	2020-09-06 12:38:40.000000000 +0200
+++ xfstests-dev/src/Makefile	2020-09-11 17:39:04.000000000 +0200
@@ -17,7 +17,8 @@ TARGETS = dirstress fill fill2 getpagesi
 	t_mmap_cow_race t_mmap_fallocate fsync-err t_mmap_write_ro \
 	t_ext4_dax_journal_corruption t_ext4_dax_inline_corruption \
 	t_ofd_locks t_mmap_collision mmap-write-concurrent \
-	t_get_file_time t_create_short_dirs t_create_long_dirs
+	t_get_file_time t_create_short_dirs t_create_long_dirs \
+	mmap-timestamp
 
 LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \
Index: xfstests-dev/src/mmap-timestamp.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ xfstests-dev/src/mmap-timestamp.c	2020-09-11 18:21:40.000000000 +0200
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 Red Hat, Inc. All Rights reserved.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#define FILE_NAME	argv[1]
+
+static struct stat st1, st2;
+
+int main(int argc, char *argv[])
+{
+	int h, r;
+	char *map;
+	unlink(FILE_NAME);
+	h = creat(FILE_NAME, 0600);
+	if (h == -1) perror("creat"), exit(1);
+	r = write(h, "x", 1);
+	if (r != 1) perror("write"), exit(1);
+	if (close(h)) perror("close"), exit(1);
+	h = open(FILE_NAME, O_RDWR);
+	if (h == -1) perror("open"), exit(1);
+
+	map = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_PRIVATE, h, 0);
+	if (map == MAP_FAILED) perror("mmap"), exit(1);
+	if (fstat(h, &st1)) perror("fstat"), exit(1);
+	sleep(2);
+	*map = 'y';
+	if (fstat(h, &st2)) perror("fstat"), exit(1);
+	if (st1.st_mtime != st2.st_mtime) fprintf(stderr, "BUG: COW fault changed mtime!\n"), exit(1);
+	if (st1.st_ctime != st2.st_ctime) fprintf(stderr, "BUG: COW fault changed ctime!\n"), exit(1);
+	if (munmap(map, 4096)) perror("munmap"), exit(1);
+
+	map = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, h, 0);
+	if (map == MAP_FAILED) perror("mmap"), exit(1);
+	if (fstat(h, &st1)) perror("fstat"), exit(1);
+	sleep(2);
+	*map = 'z';
+	if (msync(map, 4096, MS_SYNC)) perror("msync"), exit(1);
+	if (fstat(h, &st2)) perror("fstat"), exit(1);
+	if (st1.st_mtime == st2.st_mtime) fprintf(stderr, "BUG: Shared fault did not change mtime!\n"), exit(1);
+	if (st1.st_ctime == st2.st_ctime) fprintf(stderr, "BUG: Shared fault did not change ctime!\n"), exit(1);
+	if (munmap(map, 4096)) perror("munmap"), exit(1);
+
+	if (close(h)) perror("close"), exit(1);
+	if (unlink(FILE_NAME)) perror("unlink"), exit(1);
+	return 0;
+}
Index: xfstests-dev/tests/generic/609
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ xfstests-dev/tests/generic/609	2020-09-11 18:30:30.000000000 +0200
@@ -0,0 +1,40 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2020 Red Hat, Inc. All Rights Reserved.
+#
+# FS QA Test No. 609
+#
+# Check ctime and mtime are not updated on COW faults
+# and that they are updated on shared faults
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+    cd /
+    rm -f $testfile
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_require_test
+
+testfile=$TEST_DIR/testfile.$seq
+
+echo "Silence is golden"
+
+$here/src/mmap-timestamp $testfile 2>&1
+
+status=0
+exit
Index: xfstests-dev/tests/generic/609.out
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ xfstests-dev/tests/generic/609.out	2020-09-11 18:24:24.000000000 +0200
@@ -0,0 +1,2 @@
+QA output created by 609
+Silence is golden
Index: xfstests-dev/tests/generic/group
===================================================================
--- xfstests-dev.orig/tests/generic/group	2020-09-06 12:38:40.000000000 +0200
+++ xfstests-dev/tests/generic/group	2020-09-11 18:25:09.000000000 +0200
@@ -611,3 +611,4 @@
 606 auto attr quick dax
 607 auto attr quick dax
 608 auto attr quick dax
+609 auto quick

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