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@ -50,6 +50,7 @@ import java.io.PrintStream;
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import java.nio.charset.Charset; |
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import java.nio.file.Files; |
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import java.nio.file.Path; |
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import java.nio.file.Paths; |
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import java.nio.file.attribute.PosixFilePermission; |
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import java.util.ArrayList; |
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import java.util.Arrays; |
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@ -58,8 +59,11 @@ import java.util.Set;
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import org.eclipse.jgit.api.errors.JGitInternalException; |
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import org.eclipse.jgit.errors.CommandFailedException; |
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import org.eclipse.jgit.errors.ConfigInvalidException; |
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import org.eclipse.jgit.lib.ConfigConstants; |
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import org.eclipse.jgit.lib.Constants; |
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import org.eclipse.jgit.lib.Repository; |
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import org.eclipse.jgit.storage.file.FileBasedConfig; |
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import org.slf4j.Logger; |
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import org.slf4j.LoggerFactory; |
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@ -74,6 +78,10 @@ public class FS_POSIX extends FS {
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private static final int DEFAULT_UMASK = 0022; |
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private volatile int umask = -1; |
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private volatile boolean supportsUnixNLink = true; |
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private volatile Boolean supportsAtomicCreateNewFile; |
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/** Default constructor. */ |
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protected FS_POSIX() { |
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} |
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@ -91,6 +99,34 @@ public class FS_POSIX extends FS {
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} |
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} |
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@SuppressWarnings("boxing") |
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private void determineAtomicFileCreationSupport() { |
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// @TODO: enhance SystemReader to support this without copying code
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Boolean ret = getAtomicFileCreationSupportOption( |
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SystemReader.getInstance().openUserConfig(null, this)); |
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if (ret == null && StringUtils.isEmptyOrNull(SystemReader.getInstance() |
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.getenv(Constants.GIT_CONFIG_NOSYSTEM_KEY))) { |
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ret = getAtomicFileCreationSupportOption( |
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SystemReader.getInstance().openSystemConfig(null, this)); |
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} |
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supportsAtomicCreateNewFile = (ret == null) || ret; |
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} |
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private Boolean getAtomicFileCreationSupportOption(FileBasedConfig config) { |
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try { |
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config.load(); |
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String value = config.getString(ConfigConstants.CONFIG_CORE_SECTION, |
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null, |
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ConfigConstants.CONFIG_KEY_SUPPORTSATOMICFILECREATION); |
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if (value == null) { |
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return null; |
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} |
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return Boolean.valueOf(StringUtils.toBoolean(value)); |
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} catch (IOException | ConfigInvalidException e) { |
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return Boolean.TRUE; |
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} |
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} |
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@Override |
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public FS newInstance() { |
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return new FS_POSIX(this); |
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@ -301,4 +337,56 @@ public class FS_POSIX extends FS {
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return hookPath.toFile(); |
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return null; |
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} |
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@Override |
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public boolean supportsAtomicCreateNewFile() { |
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if (supportsAtomicCreateNewFile == null) { |
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determineAtomicFileCreationSupport(); |
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} |
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return supportsAtomicCreateNewFile.booleanValue(); |
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} |
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@Override |
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@SuppressWarnings("boxing") |
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/** |
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* An implementation of the File#createNewFile() semantics which works also |
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* on NFS. If the config option |
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* {@code core.supportsAtomicCreateNewFile = true} (which is the default) |
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* then simply File#createNewFile() is called. |
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* |
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* But if {@code core.supportsAtomicCreateNewFile = false} then after |
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* successful creation of the lock file a hardlink to that lock file is |
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* created and the attribute nlink of the lock file is checked to be 2. If |
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* multiple clients manage to create the same lock file nlink would be |
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* greater than 2 showing the error. |
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* |
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* @see https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html
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* @since 4.5 |
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*/ |
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public boolean createNewFile(File lock) throws IOException { |
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if (!lock.createNewFile()) { |
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return false; |
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} |
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if (supportsAtomicCreateNewFile() || !supportsUnixNLink) { |
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return true; |
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} |
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Path lockPath = lock.toPath(); |
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Path link = Files.createLink(Paths.get(lock.getAbsolutePath() + ".lnk"), //$NON-NLS-1$
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lockPath); |
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try { |
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Integer nlink = (Integer) (Files.getAttribute(lockPath, |
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"unix:nlink")); //$NON-NLS-1$
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if (nlink != 2) { |
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LOG.warn("nlink of link to lock file {0} was not 2 but {1}", //$NON-NLS-1$
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lock.getPath(), nlink); |
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return false; |
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} |
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return true; |
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} catch (UnsupportedOperationException | IllegalArgumentException e) { |
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supportsUnixNLink = false; |
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return true; |
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} finally { |
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Files.delete(link); |
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} |
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} |
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} |
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Matthias Sohn
7 years ago