1 /*

     2  * Copyright (c) 2008, 2016, Oracle and/or its affiliates. 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.  Oracle designates this

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

     9  * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * 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 jdk.internal.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             String msg = (x.errno() == EMFILE) ?

    62                 "User limit of inotify instances reached or too many open files" :

    63                 x.errorString();

    64             throw new IOException(msg);

    65         }

    66 

    67         // configure inotify to be non-blocking

    68         // create socketpair used in the close mechanism

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

    70         try {

    71             configureBlocking(ifd, false);

    72             socketpair(sp);

    73             configureBlocking(sp[0], false);

    74         } catch (UnixException x) {

    75             UnixNativeDispatcher.close(ifd);

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

    77         }

    78 

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

    80         this.poller.start();

    81     }

    82 

    83     @Override

    84     WatchKey register(Path dir,

    85                       WatchEvent.Kind<?>[] events,

    86                       WatchEvent.Modifier... modifiers)

    87          throws IOException

    88     {

    89         // delegate to poller

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

    91     }

    92 

    93     @Override

    94     void implClose() throws IOException {

    95         // delegate to poller

    96         poller.close();

    97     }

    98 

    99     /**

   100      * WatchKey implementation

   101      */

   102     private static class LinuxWatchKey extends AbstractWatchKey {

   103         // inotify descriptor

   104         private final int ifd;

   105         // watch descriptor

   106         private volatile int wd;

   107 

   108         LinuxWatchKey(UnixPath dir, LinuxWatchService watcher, int ifd, int wd) {

   109             super(dir, watcher);

   110             this.ifd = ifd;

   111             this.wd = wd;

   112         }

   113 

   114         int descriptor() {

   115             return wd;

   116         }

   117 

   118         void invalidate(boolean remove) {

   119             if (remove) {

   120                 try {

   121                     inotifyRmWatch(ifd, wd);

   122                 } catch (UnixException x) {

   123                     // ignore

   124                 }

   125             }

   126             wd = -1;

   127         }

   128 

   129         @Override

   130         public boolean isValid() {

   131             return (wd != -1);

   132         }

   133 

   134         @Override

   135         public void cancel() {

   136             if (isValid()) {

   137                 // delegate to poller

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

   139             }

   140         }

   141     }

   142 

   143     /**

   144      * Background thread to read from inotify

   145      */

   146     private static class Poller extends AbstractPoller {

   147         /**

   148          * struct inotify_event {

   149          *     int          wd;

   150          *     uint32_t     mask;

   151          *     uint32_t     len;

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

   153          * } act_t;

   154          */

   155         private static final int SIZEOF_INOTIFY_EVENT  = eventSize();

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

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

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

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

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

   161 

   162         private static final int IN_MODIFY          = 0x00000002;

   163         private static final int IN_ATTRIB          = 0x00000004;

   164         private static final int IN_MOVED_FROM      = 0x00000040;

   165         private static final int IN_MOVED_TO        = 0x00000080;

   166         private static final int IN_CREATE          = 0x00000100;

   167         private static final int IN_DELETE          = 0x00000200;

   168 

   169         private static final int IN_UNMOUNT         = 0x00002000;

   170         private static final int IN_Q_OVERFLOW      = 0x00004000;

   171         private static final int IN_IGNORED         = 0x00008000;

   172 

   173         // sizeof buffer for when polling inotify

   174         private static final int BUFFER_SIZE = 8192;

   175 

   176         private final UnixFileSystem fs;

   177         private final LinuxWatchService watcher;

   178 

   179         // inotify file descriptor

   180         private final int ifd;

   181         // socketpair used to shutdown polling thread

   182         private final int socketpair[];

   183         // maps watch descriptor to Key

   184         private final Map<Integer,LinuxWatchKey> wdToKey;

   185         // address of read buffer

   186         private final long address;

   187 

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

   189             this.fs = fs;

   190             this.watcher = watcher;

   191             this.ifd = ifd;

   192             this.socketpair = sp;

   193             this.wdToKey = new HashMap<>();

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

   195         }

   196 

   197         @Override

   198         void wakeup() throws IOException {

   199             // write to socketpair to wakeup polling thread

   200             try {

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

   202             } catch (UnixException x) {

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

   204             }

   205         }

   206 

   207         @Override

   208         Object implRegister(Path obj,

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

   210                             WatchEvent.Modifier... modifiers)

   211         {

   212             UnixPath dir = (UnixPath)obj;

   213 

   214             int mask = 0;

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

   216                 if (event == StandardWatchEventKinds.ENTRY_CREATE) {

   217                     mask |= IN_CREATE | IN_MOVED_TO;

   218                     continue;

   219                 }

   220                 if (event == StandardWatchEventKinds.ENTRY_DELETE) {

   221                     mask |= IN_DELETE | IN_MOVED_FROM;

   222                     continue;

   223                 }

   224                 if (event == StandardWatchEventKinds.ENTRY_MODIFY) {

   225                     mask |= IN_MODIFY | IN_ATTRIB;

   226                     continue;

   227                 }

   228             }

   229 

   230             // no modifiers supported at this time

   231             if (modifiers.length > 0) {

   232                 for (WatchEvent.Modifier modifier: modifiers) {

   233                     if (modifier == null)

   234                         return new NullPointerException();

   235                     if (!ExtendedOptions.SENSITIVITY_HIGH.matches(modifier) &&

   236                             !ExtendedOptions.SENSITIVITY_MEDIUM.matches(modifier) &&

   237                             !ExtendedOptions.SENSITIVITY_LOW.matches(modifier)) {

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

   239                     }

   240                 }

   241             }

   242 

   243             // check file is directory

   244             UnixFileAttributes attrs = null;

   245             try {

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

   247             } catch (UnixException x) {

   248                 return x.asIOException(dir);

   249             }

   250             if (!attrs.isDirectory()) {

   251                 return new NotDirectoryException(dir.getPathForExceptionMessage());

   252             }

   253 

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

   255             int wd = -1;

   256             try {

   257                 NativeBuffer buffer =

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

   259                 try {

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

   261                 } finally {

   262                     buffer.release();

   263                 }

   264             } catch (UnixException x) {

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

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

   267                 }

   268                 return x.asIOException(dir);

   269             }

   270 

   271             // ensure watch descriptor is in map

   272             LinuxWatchKey key = wdToKey.get(wd);

   273             if (key == null) {

   274                 key = new LinuxWatchKey(dir, watcher, ifd, wd);

   275                 wdToKey.put(wd, key);

   276             }

   277             return key;

   278         }

   279 

   280         // cancel single key

   281         @Override

   282         void implCancelKey(WatchKey obj) {

   283             LinuxWatchKey key = (LinuxWatchKey)obj;

   284             if (key.isValid()) {

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

   286                 key.invalidate(true);

   287             }

   288         }

   289 

   290         // close watch service

   291         @Override

   292         void implCloseAll() {

   293             // invalidate all keys

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

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

   296             }

   297             wdToKey.clear();

   298 

   299             // free resources

   300             unsafe.freeMemory(address);

   301             UnixNativeDispatcher.close(socketpair[0]);

   302             UnixNativeDispatcher.close(socketpair[1]);

   303             UnixNativeDispatcher.close(ifd);

   304         }

   305 

   306         /**

   307          * Poller main loop

   308          */

   309         @Override

   310         public void run() {

   311             try {

   312                 for (;;) {

   313                     int nReady, bytesRead;

   314 

   315                     // wait for close or inotify event

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

   317 

   318                     // read from inotify

   319                     try {

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

   321                     } catch (UnixException x) {

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

   323                             throw x;

   324                         bytesRead = 0;

   325                     }

   326 

   327                     // iterate over buffer to decode events

   328                     int offset = 0;

   329                     while (offset < bytesRead) {

   330                         long event = address + offset;

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

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

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

   334 

   335                         // file name

   336                         UnixPath name = null;

   337                         if (len > 0) {

   338                             int actual = len;

   339 

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

   341                             // align the next event

   342                             while (actual > 0) {

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

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

   345                                     break;

   346                                 actual--;

   347                             }

   348                             if (actual > 0) {

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

   350                                 unsafe.copyMemory(null, event + OFFSETOF_NAME,

   351                                     buf, Unsafe.ARRAY_BYTE_BASE_OFFSET, actual);

   352                                 name = new UnixPath(fs, buf);

   353                             }

   354                         }

   355 

   356                         // process event

   357                         processEvent(wd, mask, name);

   358 

   359                         offset += (SIZEOF_INOTIFY_EVENT + len);

   360                     }

   361 

   362                     // process any pending requests

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

   364                         try {

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

   366                             boolean shutdown = processRequests();

   367                             if (shutdown)

   368                                 break;

   369                         } catch (UnixException x) {

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

   371                                 throw x;

   372                         }

   373                     }

   374                 }

   375             } catch (UnixException x) {

   376                 x.printStackTrace();

   377             }

   378         }

   379 

   380 

   381         /**

   382          * map inotify event to WatchEvent.Kind

   383          */

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

   385             if ((mask & IN_MODIFY) > 0)

   386                 return StandardWatchEventKinds.ENTRY_MODIFY;

   387             if ((mask & IN_ATTRIB) > 0)

   388                 return StandardWatchEventKinds.ENTRY_MODIFY;

   389             if ((mask & IN_CREATE) > 0)

   390                 return StandardWatchEventKinds.ENTRY_CREATE;

   391             if ((mask & IN_MOVED_TO) > 0)

   392                 return StandardWatchEventKinds.ENTRY_CREATE;

   393             if ((mask & IN_DELETE) > 0)

   394                 return StandardWatchEventKinds.ENTRY_DELETE;

   395             if ((mask & IN_MOVED_FROM) > 0)

   396                 return StandardWatchEventKinds.ENTRY_DELETE;

   397             return null;

   398         }

   399 

   400         /**

   401          * Process event from inotify

   402          */

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

   404             // overflow - signal all keys

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

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

   407                     entry.getValue()

   408                         .signalEvent(StandardWatchEventKinds.OVERFLOW, null);

   409                 }

   410                 return;

   411             }

   412 

   413             // lookup wd to get key

   414             LinuxWatchKey key = wdToKey.get(wd);

   415             if (key == null)

   416                 return; // should not happen

   417 

   418             // file deleted

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

   420                 wdToKey.remove(wd);

   421                 key.invalidate(false);

   422                 key.signal();

   423                 return;

   424             }

   425 

   426             // event for directory itself

   427             if (name == null)

   428                 return;

   429 

   430             // map to event and queue to key

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

   432             if (kind != null) {

   433                 key.signalEvent(kind, name);

   434             }

   435         }

   436     }

   437 

   438     // -- native methods --

   439 

   440     // sizeof inotify_event

   441     private static native int eventSize();

   442 

   443     // offsets of inotify_event

   444     private static native int[] eventOffsets();

   445 

   446     private static native int inotifyInit() throws UnixException;

   447 

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

   449         throws UnixException;

   450 

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

   452         throws UnixException;

   453 

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

   455         throws UnixException;

   456 

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

   458 

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

   460 

   461     static {

   462         AccessController.doPrivileged(new PrivilegedAction<>() {

   463             public Void run() {

   464                 System.loadLibrary("nio");

   465                 return null;

   466         }});

   467     }

   468 }