ceph/src/global/pidfile.cc

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2011 New Dream Network
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #include "common/debug.h"
  16 #include "common/errno.h"
  17 #include "common/safe_io.h"
  18 #include "global/pidfile.h"
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <sys/stat.h>
  23 #include <sys/types.h>
  24 #include <unistd.h>
  25
  26 #if defined(__FreeBSD__)
  27 #include <sys/param.h>
  28 #endif
  29
  30 #include "include/compat.h"
  31
  32 //
  33 // derr can be used for functions exclusively called from pidfile_write
  34 //
  35 // cerr must be used for functions called by pidfile_remove because
  36 // logging is not functional when it is called. cerr output is lost
  37 // when the caller is daemonized but it will show if not (-f)
  38 //
  39 #define dout_context g_ceph_context
  40 #define dout_prefix *_dout
  41 #define dout_subsys ceph_subsys_
  42
  43 struct pidfh {
  44   int pf_fd;
  45   char pf_path[PATH_MAX + 1];
  46   dev_t pf_dev;
  47   ino_t pf_ino;
  48
  49   pidfh() {
  50     reset();
  51   }
  52   ~pidfh() {
  53     remove();
  54   }
  55
  56   bool is_open() {
  57     return pf_path[0] != '\0' && pf_fd != -1;
  58   }
  59   void reset() {
  60     pf_fd = -1;
  61     memset(pf_path, 0, sizeof(pf_path));
  62     pf_dev = 0;
  63     pf_ino = 0;
  64   }
  65   int verify();
  66   int remove();
  67   int open(const ConfigProxy& conf);
  68   int write();
  69 };
  70
  71 static pidfh *pfh = nullptr;
  72
  73 int pidfh::verify() {
  74   // check that the file we opened still is the same
  75   if (pf_fd == -1)
  76     return -EINVAL;
  77   struct stat st;
  78   if (stat(pf_path, &st) == -1)
  79     return -errno;
  80   if (st.st_dev != pf_dev || st.st_ino != pf_ino)
  81     return -ESTALE;
  82   return 0;
  83 }
  84
  85 int pidfh::remove()
  86 {
  87   if (!pf_path[0])
  88     return 0;
  89
  90   int ret;
  91   if ((ret = verify()) < 0) {
  92     if (pf_fd != -1) {
  93       ::close(pf_fd);
  94       reset();
  95     }
  96     return ret;
  97   }
  98
  99   // seek to the beginning of the file before reading
 100   ret = ::lseek(pf_fd, 0, SEEK_SET);
 101   if (ret < 0) {
 102     std::cerr << __func__ << " lseek failed "
 103               << cpp_strerror(errno) << std::endl;
 104     return -errno;
 105   }
 106
 107   // check that the pid file still has our pid in it
 108   char buf[32];
 109   memset(buf, 0, sizeof(buf));
 110   ssize_t res = safe_read(pf_fd, buf, sizeof(buf));
 111   ::close(pf_fd);
 112   if (res < 0) {
 113     std::cerr << __func__ << " safe_read failed "
 114               << cpp_strerror(-res) << std::endl;
 115     return res;
 116   }
 117
 118   int a = atoi(buf);
 119   if (a != getpid()) {
 120     std::cerr << __func__ << " the pid found in the file is "
 121               << a << " which is different from getpid() "
 122               << getpid() << std::endl;
 123     return -EDOM;
 124   }
 125   ret = ::unlink(pf_path);
 126   if (ret < 0) {
 127     std::cerr << __func__ << " unlink " << pf_path << " failed "
 128               << cpp_strerror(errno) << std::endl;
 129     return -errno;
 130   }
 131   reset();
 132   return 0;
 133 }
 134
 135 int pidfh::open(const ConfigProxy& conf)
 136 {
 137   int len = snprintf(pf_path, sizeof(pf_path),
 138                     "%s", conf->pid_file.c_str());
 139
 140   if (len >= (int)sizeof(pf_path))
 141     return -ENAMETOOLONG;
 142
 143   int fd;
 144   fd = ::open(pf_path, O_CREAT|O_RDWR|O_CLOEXEC, 0644);
 145   if (fd < 0) {
 146     int err = errno;
 147     derr << __func__ << ": failed to open pid file '"
 148          << pf_path << "': " << cpp_strerror(err) << dendl;
 149     reset();
 150     return -err;
 151   }
 152   struct stat st;
 153   if (fstat(fd, &st) == -1) {
 154     int err = errno;
 155     derr << __func__ << ": failed to fstat pid file '"
 156          << pf_path << "': " << cpp_strerror(err) << dendl;
 157     ::close(fd);
 158     reset();
 159     return -err;
 160   }
 161
 162   pf_fd = fd;
 163   pf_dev = st.st_dev;
 164   pf_ino = st.st_ino;
 165
 166   struct flock l = {
 167     .l_type = F_WRLCK,
 168     .l_whence = SEEK_SET,
 169     .l_start = 0,
 170     .l_len = 0
 171   };
 172   int r = ::fcntl(pf_fd, F_SETLK, &l);
 173   if (r < 0) {
 174     if (errno == EAGAIN || errno == EACCES) {
 175       derr << __func__ << ": failed to lock pidfile "
 176            << pf_path << " because another process locked it"
 177            << "': " << cpp_strerror(errno) << dendl;
 178     } else {
 179       derr << __func__ << ": failed to lock pidfile "
 180            << pf_path << "': " << cpp_strerror(errno) << dendl;
 181     }
 182     ::close(pf_fd);
 183     reset();
 184     return -errno;
 185   }
 186   return 0;
 187 }
 188
 189 int pidfh::write()
 190 {
 191   if (!is_open())
 192     return 0;
 193
 194   char buf[32];
 195   int len = snprintf(buf, sizeof(buf), "%d\n", getpid());
 196   if (::ftruncate(pf_fd, 0) < 0) {
 197     int err = errno;
 198     derr << __func__ << ": failed to ftruncate the pid file '"
 199          << pf_path << "': " << cpp_strerror(err) << dendl;
 200     return -err;
 201   }
 202   ssize_t res = safe_write(pf_fd, buf, len);
 203   if (res < 0) {
 204     derr << __func__ << ": failed to write to pid file '"
 205          << pf_path << "': " << cpp_strerror(-res) << dendl;
 206     return res;
 207   }
 208   return 0;
 209 }
 210
 211 void pidfile_remove()
 212 {
 213   if (pfh != nullptr)
 214     delete pfh;
 215   pfh = nullptr;
 216 }
 217
 218 int pidfile_write(const ConfigProxy& conf)
 219 {
 220   if (conf->pid_file.empty()) {
 221     dout(0) << __func__ << ": ignore empty --pid-file" << dendl;
 222     return 0;
 223   }
 224
 225   ceph_assert(pfh == nullptr);
 226
 227   pfh = new pidfh();
 228   if (atexit(pidfile_remove)) {
 229     derr << __func__ << ": failed to set pidfile_remove function "
 230          << "to run at exit." << dendl;
 231     return -EINVAL;
 232   }
 233
 234   int r = pfh->open(conf);
 235   if (r != 0) {
 236     pidfile_remove();
 237     return r;
 238   }
 239
 240   r = pfh->write();
 241   if (r != 0) {
 242     pidfile_remove();
 243     return r;
 244   }
 245
 246   return 0;
 247 }