1 // SPDX-License-Identifier: CDDL-1.0
2 /*
3 * This file is part of the ZFS Event Daemon (ZED).
4 *
5 * Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
6 * Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
7 * Refer to the OpenZFS git commit log for authoritative copyright attribution.
8 *
9 * The contents of this file are subject to the terms of the
10 * Common Development and Distribution License Version 1.0 (CDDL-1.0).
11 * You can obtain a copy of the license from the top-level file
12 * "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
13 * You may not use this file except in compliance with the license.
14 */
15
16 #include <dirent.h>
17 #include <errno.h>
18 #include <fcntl.h>
19 #include <limits.h>
20 #include <string.h>
21 #include <sys/stat.h>
22 #include <sys/types.h>
23 #include <unistd.h>
24 #include "zed_file.h"
25 #include "zed_log.h"
26
27 /*
28 * Set an exclusive advisory lock on the open file descriptor [fd].
29 * Return 0 on success, 1 if a conflicting lock is held by another process,
30 * or -1 on error (with errno set).
31 */
32 int
zed_file_lock(int fd)33 zed_file_lock(int fd)
34 {
35 struct flock lock;
36
37 if (fd < 0) {
38 errno = EBADF;
39 return (-1);
40 }
41 lock.l_type = F_WRLCK;
42 lock.l_whence = SEEK_SET;
43 lock.l_start = 0;
44 lock.l_len = 0;
45
46 if (fcntl(fd, F_SETLK, &lock) < 0) {
47 if ((errno == EACCES) || (errno == EAGAIN))
48 return (1);
49
50 return (-1);
51 }
52 return (0);
53 }
54
55 /*
56 * Release an advisory lock held on the open file descriptor [fd].
57 * Return 0 on success, or -1 on error (with errno set).
58 */
59 int
zed_file_unlock(int fd)60 zed_file_unlock(int fd)
61 {
62 struct flock lock;
63
64 if (fd < 0) {
65 errno = EBADF;
66 return (-1);
67 }
68 lock.l_type = F_UNLCK;
69 lock.l_whence = SEEK_SET;
70 lock.l_start = 0;
71 lock.l_len = 0;
72
73 if (fcntl(fd, F_SETLK, &lock) < 0)
74 return (-1);
75
76 return (0);
77 }
78
79 /*
80 * Test whether an exclusive advisory lock could be obtained for the open
81 * file descriptor [fd].
82 * Return 0 if the file is not locked, >0 for the PID of another process
83 * holding a conflicting lock, or -1 on error (with errno set).
84 */
85 pid_t
zed_file_is_locked(int fd)86 zed_file_is_locked(int fd)
87 {
88 struct flock lock;
89
90 if (fd < 0) {
91 errno = EBADF;
92 return (-1);
93 }
94 lock.l_type = F_WRLCK;
95 lock.l_whence = SEEK_SET;
96 lock.l_start = 0;
97 lock.l_len = 0;
98
99 if (fcntl(fd, F_GETLK, &lock) < 0)
100 return (-1);
101
102 if (lock.l_type == F_UNLCK)
103 return (0);
104
105 return (lock.l_pid);
106 }
107
108
109 #if __APPLE__
110 #define PROC_SELF_FD "/dev/fd"
111 #else /* Linux-compatible layout */
112 #define PROC_SELF_FD "/proc/self/fd"
113 #endif
114
115 /*
116 * Close all open file descriptors greater than or equal to [lowfd].
117 * Any errors encountered while closing file descriptors are ignored.
118 */
119 void
zed_file_close_from(int lowfd)120 zed_file_close_from(int lowfd)
121 {
122 int errno_bak = errno;
123 int maxfd = 0;
124 int fd;
125 DIR *fddir;
126 struct dirent *fdent;
127
128 if ((fddir = opendir(PROC_SELF_FD)) != NULL) {
129 while ((fdent = readdir(fddir)) != NULL) {
130 fd = atoi(fdent->d_name);
131 if (fd > maxfd && fd != dirfd(fddir))
132 maxfd = fd;
133 }
134 (void) closedir(fddir);
135 } else {
136 maxfd = sysconf(_SC_OPEN_MAX);
137 }
138 for (fd = lowfd; fd < maxfd; fd++)
139 (void) close(fd);
140
141 errno = errno_bak;
142 }
143