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 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