src/unlinkd.cc

   1 /*
   2  * Copyright (C) 1996-2015 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section 02    Unlink Daemon */
  10
  11 #include "squid.h"
  12
  13 #if USE_UNLINKD
  14 #include "disk.h"
  15 #include "fd.h"
  16 #include "fde.h"
  17 #include "globals.h"
  18 #include "SquidIpc.h"
  19 #include "SquidTime.h"
  20 #include "StatCounters.h"
  21 #include "SwapDir.h"
  22 #include "tools.h"
  23 #include "xusleep.h"
  24
  25 /* This code gets linked to Squid */
  26
  27 static int unlinkd_wfd = -1;
  28 static int unlinkd_rfd = -1;
  29
  30 static void * hIpc;
  31 static pid_t pid;
  32
  33 #define UNLINKD_QUEUE_LIMIT 20
  34
  35 void
  36 unlinkdUnlink(const char *path)
  37 {
  38     char buf[MAXPATHLEN];
  39     int l;
  40     int bytes_written;
  41     static int queuelen = 0;
  42
  43     if (unlinkd_wfd < 0) {
  44         debug_trap("unlinkdUnlink: unlinkd_wfd < 0");
  45         safeunlink(path, 0);
  46         return;
  47     }
  48
  49     /*
  50      * If the queue length is greater than our limit, then we pause
  51      * for a small amount of time, hoping that unlinkd has some
  52      * feedback for us.  Maybe it just needs a slice of the CPU's
  53      * time.
  54      */
  55     if (queuelen >= UNLINKD_QUEUE_LIMIT) {
  56 #if defined(USE_EPOLL) || defined(USE_KQUEUE) || defined(USE_DEVPOLL)
  57         /*
  58          * DPW 2007-04-23
  59          * We can't use fd_set when using epoll() or kqueue().  In
  60          * these cases we block for 10 ms.
  61          */
  62         xusleep(10000);
  63 #else
  64         /*
  65          * DPW 2007-04-23
  66          * When we can use select, block for up to 100 ms.
  67          */
  68         struct timeval to;
  69         fd_set R;
  70         FD_ZERO(&R);
  71         FD_SET(unlinkd_rfd, &R);
  72         to.tv_sec = 0;
  73         to.tv_usec = 100000;
  74         select(unlinkd_rfd + 1, &R, NULL, NULL, &to);
  75 #endif
  76     }
  77
  78     /*
  79     * If there is at least one outstanding unlink request, then
  80     * try to read a response.  If there's nothing to read we'll
  81     * get an EWOULDBLOCK or whatever.  If we get a response, then
  82     * decrement the queue size by the number of newlines read.
  83     */
  84     if (queuelen > 0) {
  85         int bytes_read;
  86         int i;
  87         char rbuf[512];
  88         bytes_read = read(unlinkd_rfd, rbuf, 511);
  89
  90         if (bytes_read > 0) {
  91             rbuf[bytes_read] = '\0';
  92
  93             for (i = 0; i < bytes_read; ++i)
  94                 if ('\n' == rbuf[i])
  95                     --queuelen;
  96
  97             assert(queuelen >= 0);
  98         }
  99     }
 100
 101     l = strlen(path);
 102     assert(l < MAXPATHLEN);
 103     xstrncpy(buf, path, MAXPATHLEN);
 104     buf[l] = '\n';
 105     ++l;
 106     bytes_written = write(unlinkd_wfd, buf, l);
 107
 108     if (bytes_written < 0) {
 109         debugs(2, DBG_IMPORTANT, "unlinkdUnlink: write FD " << unlinkd_wfd << " failed: " << xstrerror());
 110         safeunlink(path, 0);
 111         return;
 112     } else if (bytes_written != l) {
 113         debugs(2, DBG_IMPORTANT, "unlinkdUnlink: FD " << unlinkd_wfd << " only wrote " << bytes_written << " of " << l << " bytes");
 114         safeunlink(path, 0);
 115         return;
 116     }
 117
 118     ++statCounter.unlink.requests;
 119     /*
 120     * Increment this syscalls counter here, even though the syscall
 121     * is executed by the helper process.  We try to be consistent
 122     * in counting unlink operations.
 123     */
 124     ++statCounter.syscalls.disk.unlinks;
 125     ++queuelen;
 126 }
 127
 128 void
 129 unlinkdClose(void)
 130 #if _SQUID_WINDOWS_
 131 {
 132
 133     if (unlinkd_wfd > -1) {
 134         debugs(2, DBG_IMPORTANT, "Closing unlinkd pipe on FD " << unlinkd_wfd);
 135         shutdown(unlinkd_wfd, SD_BOTH);
 136         comm_close(unlinkd_wfd);
 137
 138         if (unlinkd_wfd != unlinkd_rfd)
 139             comm_close(unlinkd_rfd);
 140
 141         unlinkd_wfd = -1;
 142
 143         unlinkd_rfd = -1;
 144     }
 145
 146     if (hIpc) {
 147         if (WaitForSingleObject(hIpc, 5000) != WAIT_OBJECT_0) {
 148             getCurrentTime();
 149             debugs(2, DBG_IMPORTANT, "unlinkdClose: WARNING: (unlinkd," << pid << "d) didn't exit in 5 seconds");
 150         }
 151
 152         CloseHandle(hIpc);
 153     }
 154 }
 155 #else
 156 {
 157
 158     if (unlinkd_wfd < 0)
 159         return;
 160
 161     debugs(2, DBG_IMPORTANT, "Closing unlinkd pipe on FD " << unlinkd_wfd);
 162
 163     file_close(unlinkd_wfd);
 164
 165     if (unlinkd_wfd != unlinkd_rfd)
 166         file_close(unlinkd_rfd);
 167
 168     unlinkd_wfd = -1;
 169
 170     unlinkd_rfd = -1;
 171 }
 172
 173 #endif
 174
 175 bool
 176 unlinkdNeeded(void)
 177 {
 178     // we should start unlinkd if there are any cache_dirs using it
 179     for (int i = 0; i < Config.cacheSwap.n_configured; ++i) {
 180         const RefCount<SwapDir> sd = Config.cacheSwap.swapDirs[i];
 181         if (sd->unlinkdUseful())
 182             return true;
 183     }
 184
 185     return false;
 186 }
 187
 188 void
 189 unlinkdInit(void)
 190 {
 191     if (unlinkd_wfd >= 0)
 192         return; // unlinkd already started
 193
 194     const char *args[2];
 195     Ip::Address localhost;
 196
 197     args[0] = "(unlinkd)";
 198     args[1] = NULL;
 199     localhost.setLocalhost();
 200
 201     pid = ipcCreate(
 202 #if USE_POLL && _SQUID_OSF_
 203               /* pipes and poll() don't get along on DUNIX -DW */
 204               IPC_STREAM,
 205 #elif _SQUID_WINDOWS_
 206               /* select() will fail on a pipe */
 207               IPC_TCP_SOCKET,
 208 #else
 209               /* We currently need to use FIFO.. see below */
 210               IPC_FIFO,
 211 #endif
 212               Config.Program.unlinkd,
 213               args,
 214               "unlinkd",
 215               localhost,
 216               &unlinkd_rfd,
 217               &unlinkd_wfd,
 218               &hIpc);
 219
 220     if (pid < 0)
 221         fatal("Failed to create unlinkd subprocess");
 222
 223     xusleep(250000);
 224
 225     fd_note(unlinkd_wfd, "squid -> unlinkd");
 226
 227     fd_note(unlinkd_rfd, "unlinkd -> squid");
 228
 229     commUnsetFdTimeout(unlinkd_rfd);
 230     commUnsetFdTimeout(unlinkd_wfd);
 231
 232     /*
 233     * unlinkd_rfd should already be non-blocking because of
 234     * ipcCreate.  We change unlinkd_wfd to blocking mode because
 235     * we never want to lose an unlink request, and we don't have
 236     * code to retry if we get EWOULDBLOCK.  Unfortunately, we can
 237     * do this only for the IPC_FIFO case.
 238     */
 239     assert(fd_table[unlinkd_rfd].flags.nonblocking);
 240
 241     if (FD_PIPE == fd_table[unlinkd_wfd].type)
 242         commUnsetNonBlocking(unlinkd_wfd);
 243
 244     debugs(2, DBG_IMPORTANT, "Unlinkd pipe opened on FD " << unlinkd_wfd);
 245
 246 #if _SQUID_WINDOWS_
 247
 248     debugs(2, 4, "Unlinkd handle: 0x" << std::hex << hIpc << std::dec << ", PID: " << pid);
 249
 250 #endif
 251
 252 }
 253 #endif /* USE_UNLINKD */
 254