cmd/zed/zed_file.c

   1 /*
   2  * This file is part of the ZFS Event Daemon (ZED).
   3  *
   4  * Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
   5  * Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
   6  * Refer to the ZoL git commit log for authoritative copyright attribution.
   7  *
   8  * The contents of this file are subject to the terms of the
   9  * Common Development and Distribution License Version 1.0 (CDDL-1.0).
  10  * You can obtain a copy of the license from the top-level file
  11  * "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
  12  * You may not use this file except in compliance with the license.
  13  */
  14
  15 #include <errno.h>
  16 #include <fcntl.h>
  17 #include <limits.h>
  18 #include <string.h>
  19 #include <sys/resource.h>
  20 #include <sys/stat.h>
  21 #include <sys/types.h>
  22 #include <unistd.h>
  23 #include "zed_file.h"
  24 #include "zed_log.h"
  25
  26 /*
  27  * Read up to [n] bytes from [fd] into [buf].
  28  * Return the number of bytes read, 0 on EOF, or -1 on error.
  29  */
  30 ssize_t
  31 zed_file_read_n(int fd, void *buf, size_t n)
  32 {
  33         unsigned char *p;
  34         size_t n_left;
  35         ssize_t n_read;
  36
  37         p = buf;
  38         n_left = n;
  39         while (n_left > 0) {
  40                 if ((n_read = read(fd, p, n_left)) < 0) {
  41                         if (errno == EINTR)
  42                                 continue;
  43                         else
  44                                 return (-1);
  45
  46                 } else if (n_read == 0) {
  47                         break;
  48                 }
  49                 n_left -= n_read;
  50                 p += n_read;
  51         }
  52         return (n - n_left);
  53 }
  54
  55 /*
  56  * Write [n] bytes from [buf] out to [fd].
  57  * Return the number of bytes written, or -1 on error.
  58  */
  59 ssize_t
  60 zed_file_write_n(int fd, void *buf, size_t n)
  61 {
  62         const unsigned char *p;
  63         size_t n_left;
  64         ssize_t n_written;
  65
  66         p = buf;
  67         n_left = n;
  68         while (n_left > 0) {
  69                 if ((n_written = write(fd, p, n_left)) < 0) {
  70                         if (errno == EINTR)
  71                                 continue;
  72                         else
  73                                 return (-1);
  74
  75                 }
  76                 n_left -= n_written;
  77                 p += n_written;
  78         }
  79         return (n);
  80 }
  81
  82 /*
  83  * Set an exclusive advisory lock on the open file descriptor [fd].
  84  * Return 0 on success, 1 if a conflicting lock is held by another process,
  85  * or -1 on error (with errno set).
  86  */
  87 int
  88 zed_file_lock(int fd)
  89 {
  90         struct flock lock;
  91
  92         if (fd < 0) {
  93                 errno = EBADF;
  94                 return (-1);
  95         }
  96         lock.l_type = F_WRLCK;
  97         lock.l_whence = SEEK_SET;
  98         lock.l_start = 0;
  99         lock.l_len = 0;
 100
 101         if (fcntl(fd, F_SETLK, &lock) < 0) {
 102                 if ((errno == EACCES) || (errno == EAGAIN))
 103                         return (1);
 104
 105                 return (-1);
 106         }
 107         return (0);
 108 }
 109
 110 /*
 111  * Release an advisory lock held on the open file descriptor [fd].
 112  * Return 0 on success, or -1 on error (with errno set).
 113  */
 114 int
 115 zed_file_unlock(int fd)
 116 {
 117         struct flock lock;
 118
 119         if (fd < 0) {
 120                 errno = EBADF;
 121                 return (-1);
 122         }
 123         lock.l_type = F_UNLCK;
 124         lock.l_whence = SEEK_SET;
 125         lock.l_start = 0;
 126         lock.l_len = 0;
 127
 128         if (fcntl(fd, F_SETLK, &lock) < 0)
 129                 return (-1);
 130
 131         return (0);
 132 }
 133
 134 /*
 135  * Test whether an exclusive advisory lock could be obtained for the open
 136  * file descriptor [fd].
 137  * Return 0 if the file is not locked, >0 for the PID of another process
 138  * holding a conflicting lock, or -1 on error (with errno set).
 139  */
 140 pid_t
 141 zed_file_is_locked(int fd)
 142 {
 143         struct flock lock;
 144
 145         if (fd < 0) {
 146                 errno = EBADF;
 147                 return (-1);
 148         }
 149         lock.l_type = F_WRLCK;
 150         lock.l_whence = SEEK_SET;
 151         lock.l_start = 0;
 152         lock.l_len = 0;
 153
 154         if (fcntl(fd, F_GETLK, &lock) < 0)
 155                 return (-1);
 156
 157         if (lock.l_type == F_UNLCK)
 158                 return (0);
 159
 160         return (lock.l_pid);
 161 }
 162
 163 /*
 164  * Close all open file descriptors greater than or equal to [lowfd].
 165  * Any errors encountered while closing file descriptors are ignored.
 166  */
 167 void
 168 zed_file_close_from(int lowfd)
 169 {
 170         const int maxfd_def = 256;
 171         int errno_bak;
 172         struct rlimit rl;
 173         int maxfd;
 174         int fd;
 175
 176         errno_bak = errno;
 177
 178         if (getrlimit(RLIMIT_NOFILE, &rl) < 0) {
 179                 maxfd = maxfd_def;
 180         } else if (rl.rlim_max == RLIM_INFINITY) {
 181                 maxfd = maxfd_def;
 182         } else {
 183                 maxfd = rl.rlim_max;
 184         }
 185         for (fd = lowfd; fd < maxfd; fd++)
 186                 (void) close(fd);
 187
 188         errno = errno_bak;
 189 }
 190
 191 /*
 192  * Set the CLOEXEC flag on file descriptor [fd] so it will be automatically
 193  * closed upon successful execution of one of the exec functions.
 194  * Return 0 on success, or -1 on error.
 195  *
 196  * FIXME: No longer needed?
 197  */
 198 int
 199 zed_file_close_on_exec(int fd)
 200 {
 201         int flags;
 202
 203         if (fd < 0) {
 204                 errno = EBADF;
 205                 return (-1);
 206         }
 207         flags = fcntl(fd, F_GETFD);
 208         if (flags == -1)
 209                 return (-1);
 210
 211         flags |= FD_CLOEXEC;
 212
 213         if (fcntl(fd, F_SETFD, flags) == -1)
 214                 return (-1);
 215
 216         return (0);
 217 }