1 // SPDX-License-Identifier: CDDL-1.0
2 /*
3 * CDDL HEADER START
4 *
5 * The contents of this file are subject to the terms of the
6 * Common Development and Distribution License (the "License").
7 * You may not use this file except in compliance with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://opensource.org/licenses/CDDL-1.0.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22
23 /*
24 * Copyright (c) 2025, Klara, Inc.
25 */
26
27 /*
28 * Tests async writeback behaviour. Creates a file, maps it into memory, and
29 * dirties every page within it. Then, calls ftruncate() to collapse the file
30 * back down to 0. This causes the kernel to begin writeback on the dirty
31 * pages so they can be freed, before it can complete the ftruncate() call.
32 * None of these are sync operations, so they should avoid the various "force
33 * flush" codepaths.
34 */
35
36 #include <unistd.h>
37 #include <fcntl.h>
38 #include <sys/stat.h>
39 #include <sys/mman.h>
40 #include <stdlib.h>
41 #include <stdio.h>
42
43 #define _pdfail(f, l, s) \
44 do { perror("[" f "#" #l "] " s); exit(2); } while (0)
45 #define pdfail(str) _pdfail(__FILE__, __LINE__, str)
46
47 int
main(int argc,char ** argv)48 main(int argc, char **argv) {
49 if (argc != 3) {
50 printf("usage: mmap_ftruncate <file> <size>\n");
51 exit(2);
52 }
53
54 const char *file = argv[1];
55
56 char *end;
57 off_t sz = strtoull(argv[2], &end, 0);
58 if (end == argv[2] || *end != '\0' || sz == 0) {
59 fprintf(stderr, "E: invalid size");
60 exit(2);
61 }
62
63 int fd = open(file, O_CREAT|O_TRUNC|O_RDWR, S_IRUSR|S_IWUSR);
64 if (fd < 0)
65 pdfail("open");
66
67 if (ftruncate(fd, sz) < 0)
68 pdfail("ftruncate");
69
70 char *p = mmap(NULL, sz, PROT_WRITE, MAP_SHARED, fd, 0);
71 if (p == MAP_FAILED)
72 pdfail("mmap");
73
74 for (off_t off = 0; off < sz; off += 4096)
75 p[off] = 1;
76
77 if (ftruncate(fd, 0) < 0)
78 pdfail("ftruncate");
79
80 if (munmap(p, sz) < 0)
81 pdfail("munmap");
82
83 close(fd);
84 return (0);
85 }
86