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.file.FileAlreadyExistsException;
  21. import java.nio.file.FileStore;
  22. import java.nio.file.FileSystemException;
  23. import java.nio.file.Files;
  24. import java.nio.file.InvalidPathException;
  25. import java.nio.file.Path;
  26. import java.nio.file.Paths;
  27. import java.nio.file.attribute.PosixFilePermission;
  28. import java.text.MessageFormat;
  29. import java.util.ArrayList;
  30. import java.util.Arrays;
  31. import java.util.List;
  32. import java.util.Map;
  33. import java.util.Optional;
  34. import java.util.Set;
  35. import java.util.UUID;
  36. import java.util.concurrent.ConcurrentHashMap;

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

  48. /**
  49.  * Base FS for POSIX based systems
  50.  *
  51.  * @since 3.0
  52.  */
  53. public class FS_POSIX extends FS {
  54.     private static final Logger LOG = LoggerFactory.getLogger(FS_POSIX.class);

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

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

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

  63.     private volatile AtomicFileCreation supportsAtomicFileCreation = AtomicFileCreation.UNDEFINED;

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

  69.     /**
  70.      * Default constructor.
  71.      */
  72.     protected FS_POSIX() {
  73.     }

  75.     /**
  76.      * Constructor
  77.      *
  78.      * @param src
  79.      *            FS to copy some settings from
  80.      */
  81.     protected FS_POSIX(FS src) {
  82.         super(src);
  83.         if (src instanceof FS_POSIX) {
  84.             umask = ((FS_POSIX) src).umask;
  85.         }
  86.     }

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

  94.     /**
  95.      * Set the umask, overriding any value observed from the shell.
  96.      *
  97.      * @param umask
  98.      *            mask to apply when creating files.
  99.      * @since 4.0
  100.      */
  101.     public void setUmask(int umask) {
  102.         this.umask = umask;
  103.     }

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

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

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

  142.         if (SystemReader.getInstance().isMacOS()) {
  143.             if (gitExe == null
  144.                     || DEFAULT_GIT_LOCATION.equals(gitExe.getPath())) {
  145.                 if (searchPath(path, "bash") != null) { //$NON-NLS-1$
  146.                     // On MacOSX, PATH is shorter when Eclipse is launched from the
  147.                     // Finder than from a terminal. Therefore try to launch bash as a
  148.                     // login shell and search using that.
  149.                     try {
  150.                         String w = readPipe(userHome(),
  151.                             new String[]{"bash", "--login", "-c", "which git"}, // //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
  152.                                 SystemReader.getInstance().getDefaultCharset()
  153.                                         .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.                             SystemReader.getInstance().getDefaultCharset()
  172.                                     .name());
  173.                     if (StringUtils.isEmptyOrNull(w)) {
  174.                         gitExe = null;
  175.                     } else {
  176.                         File realGitExe = new File(new File(w),
  177.                                 DEFAULT_GIT_LOCATION.substring(1));
  178.                         if (!realGitExe.exists()) {
  179.                             gitExe = null;
  180.                         }
  181.                     }
  182.                 } catch (CommandFailedException e) {
  183.                     gitExe = null;
  184.                 }
  185.             }
  186.         }

  188.         return gitExe;
  189.     }

  191.     /** {@inheritDoc} */
  192.     @Override
  193.     public boolean isCaseSensitive() {
  194.         return !SystemReader.getInstance().isMacOS();
  195.     }

  197.     /** {@inheritDoc} */
  198.     @Override
  199.     public boolean supportsExecute() {
  200.         return true;
  201.     }

  203.     /** {@inheritDoc} */
  204.     @Override
  205.     public boolean canExecute(File f) {
  206.         return FileUtils.canExecute(f);
  207.     }

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

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

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

  224.             int mask = umask();
  225.             apply(pset, mask, PosixFilePermission.GROUP_EXECUTE, 1 << 3);
  226.             apply(pset, mask, PosixFilePermission.OTHERS_EXECUTE, 1);
  227.             Files.setPosixFilePermissions(path, pset);
  228.             return true;
  229.         } catch (IOException e) {
  230.             // The interface doesn't allow to throw IOException
  231.             final boolean debug = Boolean.parseBoolean(SystemReader
  232.                     .getInstance().getProperty("jgit.fs.debug")); //$NON-NLS-1$
  233.             if (debug)
  234.                 System.err.println(e);
  235.             return false;
  236.         }
  237.     }

  239.     private static void apply(Set<PosixFilePermission> set,
  240.             int umask, PosixFilePermission perm, int test) {
  241.         if ((umask & test) == 0) {
  242.             // If bit is clear in umask, permission is allowed.
  243.             set.add(perm);
  244.         } else {
  245.             // If bit is set in umask, permission is denied.
  246.             set.remove(perm);
  247.         }
  248.     }

  250.     /** {@inheritDoc} */
  251.     @Override
  252.     public ProcessBuilder runInShell(String cmd, String[] args) {
  253.         List<String> argv = new ArrayList<>(4 + args.length);
  254.         argv.add("sh"); //$NON-NLS-1$
  255.         argv.add("-c"); //$NON-NLS-1$
  256.         argv.add(cmd + " \"$@\""); //$NON-NLS-1$
  257.         argv.add(cmd);
  258.         argv.addAll(Arrays.asList(args));
  259.         ProcessBuilder proc = new ProcessBuilder();
  260.         proc.command(argv);
  261.         return proc;
  262.     }

  264.     @Override
  265.     String shellQuote(String cmd) {
  266.         return QuotedString.BOURNE.quote(cmd);
  267.     }

  269.     /** {@inheritDoc} */
  270.     @Override
  271.     public ProcessResult runHookIfPresent(Repository repository, String hookName,
  272.             String[] args, OutputStream outRedirect, OutputStream errRedirect,
  273.             String stdinArgs) throws JGitInternalException {
  274.         return internalRunHookIfPresent(repository, hookName, args, outRedirect,
  275.                 errRedirect, stdinArgs);
  276.     }

  278.     /** {@inheritDoc} */
  279.     @Override
  280.     public boolean retryFailedLockFileCommit() {
  281.         return false;
  282.     }

  284.     /** {@inheritDoc} */
  285.     @Override
  286.     public void setHidden(File path, boolean hidden) throws IOException {
  287.         // no action on POSIX
  288.     }

  290.     /** {@inheritDoc} */
  291.     @Override
  292.     public Attributes getAttributes(File path) {
  293.         return FileUtils.getFileAttributesPosix(this, path);
  294.     }

  296.     /** {@inheritDoc} */
  297.     @Override
  298.     public File normalize(File file) {
  299.         return FileUtils.normalize(file);
  300.     }

  302.     /** {@inheritDoc} */
  303.     @Override
  304.     public String normalize(String name) {
  305.         return FileUtils.normalize(name);
  306.     }

  308.     /** {@inheritDoc} */
  309.     @Override
  310.     public boolean supportsAtomicCreateNewFile() {
  311.         if (supportsAtomicFileCreation == AtomicFileCreation.UNDEFINED) {
  312.             try {
  313.                 StoredConfig config = SystemReader.getInstance().getUserConfig();
  314.                 String value = config.getString(CONFIG_CORE_SECTION, null,
  315.                         CONFIG_KEY_SUPPORTSATOMICFILECREATION);
  316.                 if (value != null) {
  317.                     supportsAtomicFileCreation = StringUtils.toBoolean(value)
  318.                             ? AtomicFileCreation.SUPPORTED
  319.                             : AtomicFileCreation.NOT_SUPPORTED;
  320.                 } else {
  321.                     supportsAtomicFileCreation = AtomicFileCreation.SUPPORTED;
  322.                 }
  323.             } catch (IOException | ConfigInvalidException e) {
  324.                 LOG.warn(JGitText.get().assumeAtomicCreateNewFile, e);
  325.                 supportsAtomicFileCreation = AtomicFileCreation.SUPPORTED;
  326.             }
  327.         }
  328.         return supportsAtomicFileCreation == AtomicFileCreation.SUPPORTED;
  329.     }

  331.     @Override
  332.     @SuppressWarnings("boxing")
  333.     /**
  334.      * {@inheritDoc}
  335.      * <p>
  336.      * An implementation of the File#createNewFile() semantics which works also
  337.      * on NFS. If the config option
  338.      * {@code core.supportsAtomicCreateNewFile = true} (which is the default)
  339.      * then simply File#createNewFile() is called.
  340.      *
  341.      * But if {@code core.supportsAtomicCreateNewFile = false} then after
  342.      * successful creation of the lock file a hard link to that lock file is
  343.      * created and the attribute nlink of the lock file is checked to be 2. If
  344.      * multiple clients manage to create the same lock file nlink would be
  345.      * greater than 2 showing the error.
  346.      *
  347.      * @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html"
  348.      *
  349.      * @deprecated use {@link FS_POSIX#createNewFileAtomic(File)} instead
  350.      * @since 4.5
  351.      */
  352.     @Deprecated
  353.     public boolean createNewFile(File lock) throws IOException {
  354.         if (!lock.createNewFile()) {
  355.             return false;
  356.         }
  357.         if (supportsAtomicCreateNewFile()) {
  358.             return true;
  359.         }
  360.         Path lockPath = lock.toPath();
  361.         Path link = null;
  362.         FileStore store = null;
  363.         try {
  364.             store = Files.getFileStore(lockPath);
  365.         } catch (SecurityException e) {
  366.             return true;
  367.         }
  368.         try {
  369.             Boolean canLink = CAN_HARD_LINK.computeIfAbsent(store,
  370.                     s -> Boolean.TRUE);
  371.             if (Boolean.FALSE.equals(canLink)) {
  372.                 return true;
  373.             }
  374.             link = Files.createLink(
  375.                     Paths.get(lock.getAbsolutePath() + ".lnk"), //$NON-NLS-1$
  376.                     lockPath);
  377.             Integer nlink = (Integer) (Files.getAttribute(lockPath,
  378.                     "unix:nlink")); //$NON-NLS-1$
  379.             if (nlink > 2) {
  380.                 LOG.warn(MessageFormat.format(
  381.                         JGitText.get().failedAtomicFileCreation, lockPath,
  382.                         nlink));
  383.                 return false;
  384.             } else if (nlink < 2) {
  385.                 CAN_HARD_LINK.put(store, Boolean.FALSE);
  386.             }
  387.             return true;
  388.         } catch (UnsupportedOperationException | IllegalArgumentException e) {
  389.             CAN_HARD_LINK.put(store, Boolean.FALSE);
  390.             return true;
  391.         } finally {
  392.             if (link != null) {
  393.                 Files.delete(link);
  394.             }
  395.         }
  396.     }

  398.     /**
  399.      * {@inheritDoc}
  400.      * <p>
  401.      * An implementation of the File#createNewFile() semantics which can create
  402.      * a unique file atomically also on NFS. If the config option
  403.      * {@code core.supportsAtomicCreateNewFile = true} (which is the default)
  404.      * then simply Files#createFile() is called.
  405.      *
  406.      * But if {@code core.supportsAtomicCreateNewFile = false} then after
  407.      * successful creation of the lock file a hard link to that lock file is
  408.      * created and the attribute nlink of the lock file is checked to be 2. If
  409.      * multiple clients manage to create the same lock file nlink would be
  410.      * greater than 2 showing the error. The hard link needs to be retained
  411.      * until the corresponding file is no longer needed in order to prevent that
  412.      * another process can create the same file concurrently using another NFS
  413.      * client which might not yet see the file due to caching.
  414.      *
  415.      * @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html"
  416.      * @param file
  417.      *            the unique file to be created atomically
  418.      * @return LockToken this lock token must be held until the file is no
  419.      *         longer needed
  420.      * @throws IOException
  421.      * @since 5.0
  422.      */
  423.     @Override
  424.     public LockToken createNewFileAtomic(File file) throws IOException {
  425.         Path path;
  426.         try {
  427.             path = file.toPath();
  428.             Files.createFile(path);
  429.         } catch (FileAlreadyExistsException | InvalidPathException e) {
  430.             return token(false, null);
  431.         }
  432.         if (supportsAtomicCreateNewFile()) {
  433.             return token(true, null);
  434.         }
  435.         Path link = null;
  436.         FileStore store = null;
  437.         try {
  438.             store = Files.getFileStore(path);
  439.         } catch (SecurityException e) {
  440.             return token(true, null);
  441.         }
  442.         try {
  443.             Boolean canLink = CAN_HARD_LINK.computeIfAbsent(store,
  444.                     s -> Boolean.TRUE);
  445.             if (Boolean.FALSE.equals(canLink)) {
  446.                 return token(true, null);
  447.             }
  448.             link = Files.createLink(Paths.get(uniqueLinkPath(file)), path);
  449.             Integer nlink = (Integer) (Files.getAttribute(path,
  450.                     "unix:nlink")); //$NON-NLS-1$
  451.             if (nlink.intValue() > 2) {
  452.                 LOG.warn(MessageFormat.format(
  453.                         JGitText.get().failedAtomicFileCreation, path, nlink));
  454.                 return token(false, link);
  455.             } else if (nlink.intValue() < 2) {
  456.                 CAN_HARD_LINK.put(store, Boolean.FALSE);
  457.             }
  458.             return token(true, link);
  459.         } catch (UnsupportedOperationException | IllegalArgumentException
  460.                 | FileSystemException | SecurityException e) {
  461.             CAN_HARD_LINK.put(store, Boolean.FALSE);
  462.             return token(true, link);
  463.         }
  464.     }

  466.     private static LockToken token(boolean created, @Nullable Path p) {
  467.         return ((p != null) && Files.exists(p))
  468.                 ? new LockToken(created, Optional.of(p))
  469.                 : new LockToken(created, Optional.empty());
  470.     }

  472.     private static String uniqueLinkPath(File file) {
  473.         UUID id = UUID.randomUUID();
  474.         return file.getAbsolutePath() + "." //$NON-NLS-1$
  475.                 + Long.toHexString(id.getMostSignificantBits())
  476.                 + Long.toHexString(id.getLeastSignificantBits());
  477.     }
  478. }
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