FS_POSIX.java

  1. /*
  2.  * Copyright (C) 2010, Robin Rosenberg and others
  3.  *
  4.  * This program and the accompanying materials are made available under the
  5.  * terms of the Eclipse Distribution License v. 1.0 which is available at
  6.  * https://www.eclipse.org/org/documents/edl-v10.php.
  7.  *
  8.  * SPDX-License-Identifier: BSD-3-Clause
  9.  */
  10. package org.eclipse.jgit.util;

  12. import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_CORE_SECTION;
  13. import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_SUPPORTSATOMICFILECREATION;

  15. import java.io.BufferedReader;
  16. import java.io.File;
  17. import java.io.IOException;
  18. import java.io.InputStreamReader;
  19. import java.io.OutputStream;
  20. import java.nio.charset.Charset;
  21. import java.nio.file.FileAlreadyExistsException;
  22. import java.nio.file.FileStore;
  23. import java.nio.file.FileSystemException;
  24. import java.nio.file.Files;
  25. import java.nio.file.InvalidPathException;
  26. import java.nio.file.Path;
  27. import java.nio.file.Paths;
  28. import java.nio.file.attribute.PosixFilePermission;
  29. import java.text.MessageFormat;
  30. import java.util.ArrayList;
  31. import java.util.Arrays;
  32. import java.util.List;
  33. import java.util.Map;
  34. import java.util.Optional;
  35. import java.util.Set;
  36. import java.util.UUID;
  37. import java.util.concurrent.ConcurrentHashMap;

  39. import org.eclipse.jgit.annotations.Nullable;
  40. import org.eclipse.jgit.api.errors.JGitInternalException;
  41. import org.eclipse.jgit.errors.CommandFailedException;
  42. import org.eclipse.jgit.errors.ConfigInvalidException;
  43. import org.eclipse.jgit.internal.JGitText;
  44. import org.eclipse.jgit.lib.Repository;
  45. import org.eclipse.jgit.lib.StoredConfig;
  46. import org.slf4j.Logger;
  47. import org.slf4j.LoggerFactory;

  49. /**
  50.  * Base FS for POSIX based systems
  51.  *
  52.  * @since 3.0
  53.  */
  54. public class FS_POSIX extends FS {
  55.     private static final Logger LOG = LoggerFactory.getLogger(FS_POSIX.class);

  57.     private static final String DEFAULT_GIT_LOCATION = "/usr/bin/git"; //$NON-NLS-1$

  59.     private static final int DEFAULT_UMASK = 0022;
  60.     private volatile int umask = -1;

  62.     private static final Map<FileStore, Boolean> CAN_HARD_LINK = new ConcurrentHashMap<>();

  64.     private volatile AtomicFileCreation supportsAtomicFileCreation = AtomicFileCreation.UNDEFINED;

  66.     private enum AtomicFileCreation {
  67.         SUPPORTED, NOT_SUPPORTED, UNDEFINED
  68.     }

  70.     /**
  71.      * Default constructor.
  72.      */
  73.     protected FS_POSIX() {
  74.     }

  76.     /**
  77.      * Constructor
  78.      *
  79.      * @param src
  80.      *            FS to copy some settings from
  81.      */
  82.     protected FS_POSIX(FS src) {
  83.         super(src);
  84.         if (src instanceof FS_POSIX) {
  85.             umask = ((FS_POSIX) src).umask;
  86.         }
  87.     }

  89.     /** {@inheritDoc} */
  90.     @Override
  91.     public FS newInstance() {
  92.         return new FS_POSIX(this);
  93.     }

  95.     /**
  96.      * Set the umask, overriding any value observed from the shell.
  97.      *
  98.      * @param umask
  99.      *            mask to apply when creating files.
  100.      * @since 4.0
  101.      */
  102.     public void setUmask(int umask) {
  103.         this.umask = umask;
  104.     }

  106.     private int umask() {
  107.         int u = umask;
  108.         if (u == -1) {
  109.             u = readUmask();
  110.             umask = u;
  111.         }
  112.         return u;
  113.     }

  115.     /** @return mask returned from running {@code umask} command in shell. */
  116.     private static int readUmask() {
  117.         try {
  118.             Process p = Runtime.getRuntime().exec(
  119.                     new String[] { "sh", "-c", "umask" }, //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
  120.                     null, null);
  121.             try (BufferedReader lineRead = new BufferedReader(
  122.                     new InputStreamReader(p.getInputStream(), Charset
  123.                             .defaultCharset().name()))) {
  124.                 if (p.waitFor() == 0) {
  125.                     String s = lineRead.readLine();
  126.                     if (s != null && s.matches("0?\\d{3}")) { //$NON-NLS-1$
  127.                         return Integer.parseInt(s, 8);
  128.                     }
  129.                 }
  130.                 return DEFAULT_UMASK;
  131.             }
  132.         } catch (Exception e) {
  133.             return DEFAULT_UMASK;
  134.         }
  135.     }

  137.     /** {@inheritDoc} */
  138.     @Override
  139.     protected File discoverGitExe() {
  140.         String path = SystemReader.getInstance().getenv("PATH"); //$NON-NLS-1$
  141.         File gitExe = searchPath(path, "git"); //$NON-NLS-1$

  143.         if (SystemReader.getInstance().isMacOS()) {
  144.             if (gitExe == null
  145.                     || DEFAULT_GIT_LOCATION.equals(gitExe.getPath())) {
  146.                 if (searchPath(path, "bash") != null) { //$NON-NLS-1$
  147.                     // On MacOSX, PATH is shorter when Eclipse is launched from the
  148.                     // Finder than from a terminal. Therefore try to launch bash as a
  149.                     // login shell and search using that.
  150.                     try {
  151.                         String w = readPipe(userHome(),
  152.                             new String[]{"bash", "--login", "-c", "which git"}, // //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
  153.                             Charset.defaultCharset().name());
  154.                         if (!StringUtils.isEmptyOrNull(w)) {
  155.                             gitExe = new File(w);
  156.                         }
  157.                     } catch (CommandFailedException e) {
  158.                         LOG.warn(e.getMessage());
  159.                     }
  160.                 }
  161.             }
  162.             if (gitExe != null
  163.                     && DEFAULT_GIT_LOCATION.equals(gitExe.getPath())) {
  164.                 // If we still have the default git exe, it's an XCode wrapper
  165.                 // that may prompt the user to install the XCode command line
  166.                 // tools if not already present. Avoid the prompt by returning
  167.                 // null if no XCode git is there.
  168.                 try {
  169.                     String w = readPipe(userHome(),
  170.                             new String[] { "xcode-select", "-p" }, //$NON-NLS-1$ //$NON-NLS-2$
  171.                             Charset.defaultCharset().name());
  172.                     if (StringUtils.isEmptyOrNull(w)) {
  173.                         gitExe = null;
  174.                     } else {
  175.                         File realGitExe = new File(new File(w),
  176.                                 DEFAULT_GIT_LOCATION.substring(1));
  177.                         if (!realGitExe.exists()) {
  178.                             gitExe = null;
  179.                         }
  180.                     }
  181.                 } catch (CommandFailedException e) {
  182.                     gitExe = null;
  183.                 }
  184.             }
  185.         }

  187.         return gitExe;
  188.     }

  190.     /** {@inheritDoc} */
  191.     @Override
  192.     public boolean isCaseSensitive() {
  193.         return !SystemReader.getInstance().isMacOS();
  194.     }

  196.     /** {@inheritDoc} */
  197.     @Override
  198.     public boolean supportsExecute() {
  199.         return true;
  200.     }

  202.     /** {@inheritDoc} */
  203.     @Override
  204.     public boolean canExecute(File f) {
  205.         return FileUtils.canExecute(f);
  206.     }

  208.     /** {@inheritDoc} */
  209.     @Override
  210.     public boolean setExecute(File f, boolean canExecute) {
  211.         if (!isFile(f))
  212.             return false;
  213.         if (!canExecute)
  214.             return f.setExecutable(false, false);

  216.         try {
  217.             Path path = FileUtils.toPath(f);
  218.             Set<PosixFilePermission> pset = Files.getPosixFilePermissions(path);

  220.             // owner (user) is always allowed to execute.
  221.             pset.add(PosixFilePermission.OWNER_EXECUTE);

  223.             int mask = umask();
  224.             apply(pset, mask, PosixFilePermission.GROUP_EXECUTE, 1 << 3);
  225.             apply(pset, mask, PosixFilePermission.OTHERS_EXECUTE, 1);
  226.             Files.setPosixFilePermissions(path, pset);
  227.             return true;
  228.         } catch (IOException e) {
  229.             // The interface doesn't allow to throw IOException
  230.             final boolean debug = Boolean.parseBoolean(SystemReader
  231.                     .getInstance().getProperty("jgit.fs.debug")); //$NON-NLS-1$
  232.             if (debug)
  233.                 System.err.println(e);
  234.             return false;
  235.         }
  236.     }

  238.     private static void apply(Set<PosixFilePermission> set,
  239.             int umask, PosixFilePermission perm, int test) {
  240.         if ((umask & test) == 0) {
  241.             // If bit is clear in umask, permission is allowed.
  242.             set.add(perm);
  243.         } else {
  244.             // If bit is set in umask, permission is denied.
  245.             set.remove(perm);
  246.         }
  247.     }

  249.     /** {@inheritDoc} */
  250.     @Override
  251.     public ProcessBuilder runInShell(String cmd, String[] args) {
  252.         List<String> argv = new ArrayList<>(4 + args.length);
  253.         argv.add("sh"); //$NON-NLS-1$
  254.         argv.add("-c"); //$NON-NLS-1$
  255.         argv.add(cmd + " \"$@\""); //$NON-NLS-1$
  256.         argv.add(cmd);
  257.         argv.addAll(Arrays.asList(args));
  258.         ProcessBuilder proc = new ProcessBuilder();
  259.         proc.command(argv);
  260.         return proc;
  261.     }

  263.     @Override
  264.     String shellQuote(String cmd) {
  265.         return QuotedString.BOURNE.quote(cmd);
  266.     }

  268.     /** {@inheritDoc} */
  269.     @Override
  270.     public ProcessResult runHookIfPresent(Repository repository, String hookName,
  271.             String[] args, OutputStream outRedirect, OutputStream errRedirect,
  272.             String stdinArgs) throws JGitInternalException {
  273.         return internalRunHookIfPresent(repository, hookName, args, outRedirect,
  274.                 errRedirect, stdinArgs);
  275.     }

  277.     /** {@inheritDoc} */
  278.     @Override
  279.     public boolean retryFailedLockFileCommit() {
  280.         return false;
  281.     }

  283.     /** {@inheritDoc} */
  284.     @Override
  285.     public void setHidden(File path, boolean hidden) throws IOException {
  286.         // no action on POSIX
  287.     }

  289.     /** {@inheritDoc} */
  290.     @Override
  291.     public Attributes getAttributes(File path) {
  292.         return FileUtils.getFileAttributesPosix(this, path);
  293.     }

  295.     /** {@inheritDoc} */
  296.     @Override
  297.     public File normalize(File file) {
  298.         return FileUtils.normalize(file);
  299.     }

  301.     /** {@inheritDoc} */
  302.     @Override
  303.     public String normalize(String name) {
  304.         return FileUtils.normalize(name);
  305.     }

  307.     /** {@inheritDoc} */
  308.     @Override
  309.     public boolean supportsAtomicCreateNewFile() {
  310.         if (supportsAtomicFileCreation == AtomicFileCreation.UNDEFINED) {
  311.             try {
  312.                 StoredConfig config = SystemReader.getInstance().getUserConfig();
  313.                 String value = config.getString(CONFIG_CORE_SECTION, null,
  314.                         CONFIG_KEY_SUPPORTSATOMICFILECREATION);
  315.                 if (value != null) {
  316.                     supportsAtomicFileCreation = StringUtils.toBoolean(value)
  317.                             ? AtomicFileCreation.SUPPORTED
  318.                             : AtomicFileCreation.NOT_SUPPORTED;
  319.                 } else {
  320.                     supportsAtomicFileCreation = AtomicFileCreation.SUPPORTED;
  321.                 }
  322.             } catch (IOException | ConfigInvalidException e) {
  323.                 LOG.warn(JGitText.get().assumeAtomicCreateNewFile, e);
  324.                 supportsAtomicFileCreation = AtomicFileCreation.SUPPORTED;
  325.             }
  326.         }
  327.         return supportsAtomicFileCreation == AtomicFileCreation.SUPPORTED;
  328.     }

  330.     @Override
  331.     @SuppressWarnings("boxing")
  332.     /**
  333.      * {@inheritDoc}
  334.      * <p>
  335.      * An implementation of the File#createNewFile() semantics which works also
  336.      * on NFS. If the config option
  337.      * {@code core.supportsAtomicCreateNewFile = true} (which is the default)
  338.      * then simply File#createNewFile() is called.
  339.      *
  340.      * But if {@code core.supportsAtomicCreateNewFile = false} then after
  341.      * successful creation of the lock file a hard link to that lock file is
  342.      * created and the attribute nlink of the lock file is checked to be 2. If
  343.      * multiple clients manage to create the same lock file nlink would be
  344.      * greater than 2 showing the error.
  345.      *
  346.      * @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html"
  347.      *
  348.      * @deprecated use {@link FS_POSIX#createNewFileAtomic(File)} instead
  349.      * @since 4.5
  350.      */
  351.     @Deprecated
  352.     public boolean createNewFile(File lock) throws IOException {
  353.         if (!lock.createNewFile()) {
  354.             return false;
  355.         }
  356.         if (supportsAtomicCreateNewFile()) {
  357.             return true;
  358.         }
  359.         Path lockPath = lock.toPath();
  360.         Path link = null;
  361.         FileStore store = null;
  362.         try {
  363.             store = Files.getFileStore(lockPath);
  364.         } catch (SecurityException e) {
  365.             return true;
  366.         }
  367.         try {
  368.             Boolean canLink = CAN_HARD_LINK.computeIfAbsent(store,
  369.                     s -> Boolean.TRUE);
  370.             if (Boolean.FALSE.equals(canLink)) {
  371.                 return true;
  372.             }
  373.             link = Files.createLink(
  374.                     Paths.get(lock.getAbsolutePath() + ".lnk"), //$NON-NLS-1$
  375.                     lockPath);
  376.             Integer nlink = (Integer) (Files.getAttribute(lockPath,
  377.                     "unix:nlink")); //$NON-NLS-1$
  378.             if (nlink > 2) {
  379.                 LOG.warn(MessageFormat.format(
  380.                         JGitText.get().failedAtomicFileCreation, lockPath,
  381.                         nlink));
  382.                 return false;
  383.             } else if (nlink < 2) {
  384.                 CAN_HARD_LINK.put(store, Boolean.FALSE);
  385.             }
  386.             return true;
  387.         } catch (UnsupportedOperationException | IllegalArgumentException e) {
  388.             CAN_HARD_LINK.put(store, Boolean.FALSE);
  389.             return true;
  390.         } finally {
  391.             if (link != null) {
  392.                 Files.delete(link);
  393.             }
  394.         }
  395.     }

  397.     /**
  398.      * {@inheritDoc}
  399.      * <p>
  400.      * An implementation of the File#createNewFile() semantics which can create
  401.      * a unique file atomically also on NFS. If the config option
  402.      * {@code core.supportsAtomicCreateNewFile = true} (which is the default)
  403.      * then simply Files#createFile() is called.
  404.      *
  405.      * But if {@code core.supportsAtomicCreateNewFile = false} then after
  406.      * successful creation of the lock file a hard link to that lock file is
  407.      * created and the attribute nlink of the lock file is checked to be 2. If
  408.      * multiple clients manage to create the same lock file nlink would be
  409.      * greater than 2 showing the error. The hard link needs to be retained
  410.      * until the corresponding file is no longer needed in order to prevent that
  411.      * another process can create the same file concurrently using another NFS
  412.      * client which might not yet see the file due to caching.
  413.      *
  414.      * @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html"
  415.      * @param file
  416.      *            the unique file to be created atomically
  417.      * @return LockToken this lock token must be held until the file is no
  418.      *         longer needed
  419.      * @throws IOException
  420.      * @since 5.0
  421.      */
  422.     @Override
  423.     public LockToken createNewFileAtomic(File file) throws IOException {
  424.         Path path;
  425.         try {
  426.             path = file.toPath();
  427.             Files.createFile(path);
  428.         } catch (FileAlreadyExistsException | InvalidPathException e) {
  429.             return token(false, null);
  430.         }
  431.         if (supportsAtomicCreateNewFile()) {
  432.             return token(true, null);
  433.         }
  434.         Path link = null;
  435.         FileStore store = null;
  436.         try {
  437.             store = Files.getFileStore(path);
  438.         } catch (SecurityException e) {
  439.             return token(true, null);
  440.         }
  441.         try {
  442.             Boolean canLink = CAN_HARD_LINK.computeIfAbsent(store,
  443.                     s -> Boolean.TRUE);
  444.             if (Boolean.FALSE.equals(canLink)) {
  445.                 return token(true, null);
  446.             }
  447.             link = Files.createLink(Paths.get(uniqueLinkPath(file)), path);
  448.             Integer nlink = (Integer) (Files.getAttribute(path,
  449.                     "unix:nlink")); //$NON-NLS-1$
  450.             if (nlink.intValue() > 2) {
  451.                 LOG.warn(MessageFormat.format(
  452.                         JGitText.get().failedAtomicFileCreation, path, nlink));
  453.                 return token(false, link);
  454.             } else if (nlink.intValue() < 2) {
  455.                 CAN_HARD_LINK.put(store, Boolean.FALSE);
  456.             }
  457.             return token(true, link);
  458.         } catch (UnsupportedOperationException | IllegalArgumentException
  459.                 | FileSystemException | SecurityException e) {
  460.             CAN_HARD_LINK.put(store, Boolean.FALSE);
  461.             return token(true, link);
  462.         }
  463.     }

  465.     private static LockToken token(boolean created, @Nullable Path p) {
  466.         return ((p != null) && Files.exists(p))
  467.                 ? new LockToken(created, Optional.of(p))
  468.                 : new LockToken(created, Optional.empty());
  469.     }

  471.     private static String uniqueLinkPath(File file) {
  472.         UUID id = UUID.randomUUID();
  473.         return file.getAbsolutePath() + "." //$NON-NLS-1$
  474.                 + Long.toHexString(id.getMostSignificantBits())
  475.                 + Long.toHexString(id.getLeastSignificantBits());
  476.     }
  477. }
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