1 /*

     2  * Copyright 2008-2009 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 package sun.nio.fs;

    27 

    28 import java.nio.file.*;

    29 import java.security.AccessController;

    30 import java.security.PrivilegedAction;

    31 import java.util.*;

    32 import java.io.IOException;

    33 import sun.misc.Unsafe;

    34 

    35 import static sun.nio.fs.UnixNativeDispatcher.*;

    36 import static sun.nio.fs.UnixConstants.*;

    37 

    38 /**

    39  * Linux implementation of WatchService based on inotify.

    40  *

    41  * In summary a background thread polls inotify plus a socket used for the wakeup

    42  * mechanism. Requests to add or remove a watch, or close the watch service,

    43  * cause the thread to wakeup and process the request. Events are processed

    44  * by the thread which causes it to signal/queue the corresponding watch keys.

    45  */

    46 

    47 class LinuxWatchService

    48     extends AbstractWatchService

    49 {

    50     private static final Unsafe unsafe = Unsafe.getUnsafe();

    51 

    52     // background thread to read change events

    53     private final Poller poller;

    54 

    55     LinuxWatchService(UnixFileSystem fs) throws IOException {

    56         // initialize inotify

    57         int ifd = - 1;

    58         try {

    59             ifd = inotifyInit();

    60         } catch (UnixException x) {

    61             throw new IOException(x.errorString());

    62         }

    63 

    64         // configure inotify to be non-blocking

    65         // create socketpair used in the close mechanism

    66         int sp[] = new int[2];

    67         try {

    68             configureBlocking(ifd, false);

    69             socketpair(sp);

    70             configureBlocking(sp[0], false);

    71         } catch (UnixException x) {

    72             UnixNativeDispatcher.close(ifd);

    73             throw new IOException(x.errorString());

    74         }

    75 

    76         this.poller = new Poller(fs, this, ifd, sp);

    77         this.poller.start();

    78     }

    79 

    80     @Override

    81     WatchKey register(Path dir,

    82                       WatchEvent.Kind<?>[] events,

    83                       WatchEvent.Modifier... modifiers)

    84          throws IOException

    85     {

    86         // delegate to poller

    87         return poller.register(dir, events, modifiers);

    88     }

    89 

    90     @Override

    91     void implClose() throws IOException {

    92         // delegate to poller

    93         poller.close();

    94     }

    95 

    96     /**

    97      * WatchKey implementation

    98      */

    99     private static class LinuxWatchKey extends AbstractWatchKey {

   100         // inotify descriptor

   101         private final int ifd;

   102         // watch descriptor

   103         private volatile int wd;

   104 

   105         LinuxWatchKey(LinuxWatchService watcher, int ifd, int wd) {

   106             super(watcher);

   107             this.ifd = ifd;

   108             this.wd = wd;

   109         }

   110 

   111         int descriptor() {

   112             return wd;

   113         }

   114 

   115         void invalidate(boolean remove) {

   116             if (remove) {

   117                 try {

   118                     inotifyRmWatch(ifd, wd);

   119                 } catch (UnixException x) {

   120                     // ignore

   121                 }

   122             }

   123             wd = -1;

   124         }

   125 

   126         @Override

   127         public boolean isValid() {

   128             return (wd != -1);

   129         }

   130 

   131         @Override

   132         public void cancel() {

   133             if (isValid()) {

   134                 // delegate to poller

   135                 ((LinuxWatchService)watcher()).poller.cancel(this);

   136             }

   137         }

   138     }

   139 

   140     /**

   141      * Background thread to read from inotify

   142      */

   143     private static class Poller extends AbstractPoller {

   144         /**

   145          * struct inotify_event {

   146          *     int          wd;

   147          *     uint32_t     mask;

   148          *     uint32_t     len;

   149          *     char name    __flexarr;  // present if len > 0

   150          * } act_t;

   151          */

   152         private static final int SIZEOF_INOTIFY_EVENT  = eventSize();

   153         private static final int[] offsets             = eventOffsets();

   154         private static final int OFFSETOF_WD           = offsets[0];

   155         private static final int OFFSETOF_MASK         = offsets[1];

   156         private static final int OFFSETOF_LEN          = offsets[3];

   157         private static final int OFFSETOF_NAME         = offsets[4];

   158 

   159         private static final int IN_MODIFY          = 0x00000002;

   160         private static final int IN_ATTRIB          = 0x00000004;

   161         private static final int IN_MOVED_FROM      = 0x00000040;

   162         private static final int IN_MOVED_TO        = 0x00000080;

   163         private static final int IN_CREATE          = 0x00000100;

   164         private static final int IN_DELETE          = 0x00000200;

   165 

   166         private static final int IN_UNMOUNT         = 0x00002000;

   167         private static final int IN_Q_OVERFLOW      = 0x00004000;

   168         private static final int IN_IGNORED         = 0x00008000;

   169 

   170         // sizeof buffer for when polling inotify

   171         private static final int BUFFER_SIZE = 8192;

   172 

   173         private final UnixFileSystem fs;

   174         private final LinuxWatchService watcher;

   175 

   176         // inotify file descriptor

   177         private final int ifd;

   178         // socketpair used to shutdown polling thread

   179         private final int socketpair[];

   180         // maps watch descriptor to Key

   181         private final Map<Integer,LinuxWatchKey> wdToKey;

   182         // address of read buffer

   183         private final long address;

   184 

   185         Poller(UnixFileSystem fs, LinuxWatchService watcher, int ifd, int[] sp) {

   186             this.fs = fs;

   187             this.watcher = watcher;

   188             this.ifd = ifd;

   189             this.socketpair = sp;

   190             this.wdToKey = new HashMap<Integer,LinuxWatchKey>();

   191             this.address = unsafe.allocateMemory(BUFFER_SIZE);

   192         }

   193 

   194         @Override

   195         void wakeup() throws IOException {

   196             // write to socketpair to wakeup polling thread

   197             try {

   198                 write(socketpair[1], address, 1);

   199             } catch (UnixException x) {

   200                 throw new IOException(x.errorString());

   201             }

   202         }

   203 

   204         @Override

   205         Object implRegister(Path obj,

   206                             Set<? extends WatchEvent.Kind<?>> events,

   207                             WatchEvent.Modifier... modifiers)

   208         {

   209             UnixPath dir = (UnixPath)obj;

   210 

   211             int mask = 0;

   212             for (WatchEvent.Kind<?> event: events) {

   213                 if (event == StandardWatchEventKind.ENTRY_CREATE) {

   214                     mask |= IN_CREATE | IN_MOVED_TO;

   215                     continue;

   216                 }

   217                 if (event == StandardWatchEventKind.ENTRY_DELETE) {

   218                     mask |= IN_DELETE | IN_MOVED_FROM;

   219                     continue;

   220                 }

   221                 if (event == StandardWatchEventKind.ENTRY_MODIFY) {

   222                     mask |= IN_MODIFY | IN_ATTRIB;

   223                     continue;

   224                 }

   225             }

   226 

   227             // no modifiers supported at this time

   228             if (modifiers.length > 0) {

   229                 for (WatchEvent.Modifier modifier: modifiers) {

   230                     if (modifier == null)

   231                         return new NullPointerException();

   232                     if (modifier instanceof com.sun.nio.file.SensitivityWatchEventModifier)

   233                         continue; // ignore

   234                     return new UnsupportedOperationException("Modifier not supported");

   235                 }

   236             }

   237 

   238             // check file is directory

   239             UnixFileAttributes attrs = null;

   240             try {

   241                 attrs = UnixFileAttributes.get(dir, true);

   242             } catch (UnixException x) {

   243                 return x.asIOException(dir);

   244             }

   245             if (!attrs.isDirectory()) {

   246                 return new NotDirectoryException(dir.getPathForExecptionMessage());

   247             }

   248 

   249             // register with inotify (replaces existing mask if already registered)

   250             int wd = -1;

   251             try {

   252                 NativeBuffer buffer =

   253                     NativeBuffers.asNativeBuffer(dir.getByteArrayForSysCalls());

   254                 try {

   255                     wd = inotifyAddWatch(ifd, buffer.address(), mask);

   256                 } finally {

   257                     buffer.release();

   258                 }

   259             } catch (UnixException x) {

   260                 if (x.errno() == ENOSPC) {

   261                     return new IOException("User limit of inotify watches reached");

   262                 }

   263                 return x.asIOException(dir);

   264             }

   265 

   266             // ensure watch descriptor is in map

   267             LinuxWatchKey key = wdToKey.get(wd);

   268             if (key == null) {

   269                 key = new LinuxWatchKey(watcher, ifd, wd);

   270                 wdToKey.put(wd, key);

   271             }

   272             return key;

   273         }

   274 

   275         // cancel single key

   276         @Override

   277         void implCancelKey(WatchKey obj) {

   278             LinuxWatchKey key = (LinuxWatchKey)obj;

   279             if (key.isValid()) {

   280                 wdToKey.remove(key.descriptor());

   281                 key.invalidate(true);

   282             }

   283         }

   284 

   285         // close watch service

   286         @Override

   287         void implCloseAll() {

   288             // invalidate all keys

   289             for (Map.Entry<Integer,LinuxWatchKey> entry: wdToKey.entrySet()) {

   290                 entry.getValue().invalidate(true);

   291             }

   292             wdToKey.clear();

   293 

   294             // free resources

   295             unsafe.freeMemory(address);

   296             UnixNativeDispatcher.close(socketpair[0]);

   297             UnixNativeDispatcher.close(socketpair[1]);

   298             UnixNativeDispatcher.close(ifd);

   299         }

   300 

   301         /**

   302          * Poller main loop

   303          */

   304         @Override

   305         public void run() {

   306             try {

   307                 for (;;) {

   308                     int nReady, bytesRead;

   309 

   310                     // wait for close or inotify event

   311                     nReady = poll(ifd, socketpair[0]);

   312 

   313                     // read from inotify

   314                     try {

   315                         bytesRead = read(ifd, address, BUFFER_SIZE);

   316                     } catch (UnixException x) {

   317                         if (x.errno() != EAGAIN)

   318                             throw x;

   319                         bytesRead = 0;

   320                     }

   321 

   322                     // process any pending requests

   323                     if ((nReady > 1) || (nReady == 1 && bytesRead == 0)) {

   324                         try {

   325                             read(socketpair[0], address, BUFFER_SIZE);

   326                             boolean shutdown = processRequests();

   327                             if (shutdown)

   328                                 break;

   329                         } catch (UnixException x) {

   330                             if (x.errno() != UnixConstants.EAGAIN)

   331                                 throw x;

   332                         }

   333                     }

   334 

   335                     // iterate over buffer to decode events

   336                     int offset = 0;

   337                     while (offset < bytesRead) {

   338                         long event = address + offset;

   339                         int wd = unsafe.getInt(event + OFFSETOF_WD);

   340                         int mask = unsafe.getInt(event + OFFSETOF_MASK);

   341                         int len = unsafe.getInt(event + OFFSETOF_LEN);

   342 

   343                         // file name

   344                         UnixPath name = null;

   345                         if (len > 0) {

   346                             int actual = len;

   347 

   348                             // null-terminated and maybe additional null bytes to

   349                             // align the next event

   350                             while (actual > 0) {

   351                                 long last = event + OFFSETOF_NAME + actual - 1;

   352                                 if (unsafe.getByte(last) != 0)

   353                                     break;

   354                                 actual--;

   355                             }

   356                             if (actual > 0) {

   357                                 byte[] buf = new byte[actual];

   358                                 unsafe.copyMemory(null, event + OFFSETOF_NAME,

   359                                     buf, Unsafe.ARRAY_BYTE_BASE_OFFSET, actual);

   360                                 name = new UnixPath(fs, buf);

   361                             }

   362                         }

   363 

   364                         // process event

   365                         processEvent(wd, mask, name);

   366 

   367                         offset += (SIZEOF_INOTIFY_EVENT + len);

   368                     }

   369                 }

   370             } catch (UnixException x) {

   371                 x.printStackTrace();

   372             }

   373         }

   374 

   375 

   376         /**

   377          * map inotify event to WatchEvent.Kind

   378          */

   379         private WatchEvent.Kind<?> maskToEventKind(int mask) {

   380             if ((mask & IN_MODIFY) > 0)

   381                 return StandardWatchEventKind.ENTRY_MODIFY;

   382             if ((mask & IN_ATTRIB) > 0)

   383                 return StandardWatchEventKind.ENTRY_MODIFY;

   384             if ((mask & IN_CREATE) > 0)

   385                 return StandardWatchEventKind.ENTRY_CREATE;

   386             if ((mask & IN_MOVED_TO) > 0)

   387                 return StandardWatchEventKind.ENTRY_CREATE;

   388             if ((mask & IN_DELETE) > 0)

   389                 return StandardWatchEventKind.ENTRY_DELETE;

   390             if ((mask & IN_MOVED_FROM) > 0)

   391                 return StandardWatchEventKind.ENTRY_DELETE;

   392             return null;

   393         }

   394 

   395         /**

   396          * Process event from inotify

   397          */

   398         private void processEvent(int wd, int mask, final UnixPath name) {

   399             // overflow - signal all keys

   400             if ((mask & IN_Q_OVERFLOW) > 0) {

   401                 for (Map.Entry<Integer,LinuxWatchKey> entry: wdToKey.entrySet()) {

   402                     entry.getValue()

   403                         .signalEvent(StandardWatchEventKind.OVERFLOW, null);

   404                 }

   405                 return;

   406             }

   407 

   408             // lookup wd to get key

   409             LinuxWatchKey key = wdToKey.get(wd);

   410             if (key == null)

   411                 return; // should not happen

   412 

   413             // file deleted

   414             if ((mask & IN_IGNORED) > 0) {

   415                 wdToKey.remove(wd);

   416                 key.invalidate(false);

   417                 key.signal();

   418                 return;

   419             }

   420 

   421             // event for directory itself

   422             if (name == null)

   423                 return;

   424 

   425             // map to event and queue to key

   426             WatchEvent.Kind<?> kind = maskToEventKind(mask);

   427             if (kind != null) {

   428                 key.signalEvent(kind, name);

   429             }

   430         }

   431     }

   432 

   433     // -- native methods --

   434 

   435     private static native void init();

   436 

   437     // sizeof inotify_event

   438     private static native int eventSize();

   439 

   440     // offsets of inotify_event

   441     private static native int[] eventOffsets();

   442 

   443     private static native int inotifyInit() throws UnixException;

   444 

   445     private static native int inotifyAddWatch(int fd, long pathAddress, int mask)

   446         throws UnixException;

   447 

   448     private static native void inotifyRmWatch(int fd, int wd)

   449         throws UnixException;

   450 

   451     private static native void configureBlocking(int fd, boolean blocking)

   452         throws UnixException;

   453 

   454     private static native void socketpair(int[] sv) throws UnixException;

   455 

   456     private static native int poll(int fd1, int fd2) throws UnixException;

   457 

   458     static {

   459         AccessController.doPrivileged(new PrivilegedAction<Void>() {

   460             public Void run() {

   461                 System.loadLibrary("nio");

   462                 return null;

   463         }});

   464         init();

   465     }

   466 }