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@ -52,14 +52,19 @@ 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.text.MessageFormat; |
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import java.util.ArrayList; |
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import java.util.Arrays; |
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import java.util.List; |
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import java.util.Optional; |
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import java.util.Set; |
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import java.util.UUID; |
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import org.eclipse.jgit.annotations.Nullable; |
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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.internal.JGitText; |
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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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@ -372,9 +377,12 @@ public class FS_POSIX extends FS {
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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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* @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html" |
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* |
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* @deprecated use {@link FS_POSIX#createNewFileAtomic(File)} instead |
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* @since 4.5 |
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*/ |
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@Deprecated |
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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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@ -383,22 +391,94 @@ public class FS_POSIX extends FS {
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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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Path link = null; |
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try { |
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link = Files.createLink( |
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Paths.get(lock.getAbsolutePath() + ".lnk"), //$NON-NLS-1$
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lockPath); |
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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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if (nlink > 2) { |
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LOG.warn("nlink of link to lock file {} was not 2 but {}", //$NON-NLS-1$
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lock.getPath(), nlink); |
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return false; |
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} else if (nlink < 2) { |
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supportsUnixNLink = 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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if (link != null) { |
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Files.delete(link); |
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} |
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} |
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} |
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/** |
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* {@inheritDoc} |
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* <p> |
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* An implementation of the File#createNewFile() semantics which can create |
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* a unique file atomically also 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 hard link 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. The hard link needs to be retained |
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* until the corresponding file is no longer needed in order to prevent that |
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* another process can create the same file concurrently using another NFS |
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* client which might not yet see the file due to caching. |
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* |
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* @see "https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html" |
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* @param file |
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* the unique file to be created atomically |
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* @return LockToken this lock token must be held until the file is no |
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* longer needed |
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* @throws IOException |
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* @since 5.0 |
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*/ |
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@Override |
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public LockToken createNewFileAtomic(File file) throws IOException { |
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if (!file.createNewFile()) { |
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return token(false, null); |
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} |
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if (supportsAtomicCreateNewFile() || !supportsUnixNLink) { |
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return token(true, null); |
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} |
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Path link = null; |
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Path path = file.toPath(); |
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try { |
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link = Files.createLink(Paths.get(uniqueLinkPath(file)), path); |
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Integer nlink = (Integer) (Files.getAttribute(path, |
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"unix:nlink")); //$NON-NLS-1$
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if (nlink.intValue() > 2) { |
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LOG.warn(MessageFormat.format( |
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JGitText.get().failedAtomicFileCreation, path, nlink)); |
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return token(false, link); |
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} else if (nlink.intValue() < 2) { |
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supportsUnixNLink = false; |
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} |
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return token(true, link); |
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} catch (UnsupportedOperationException | IllegalArgumentException e) { |
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supportsUnixNLink = false; |
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return token(true, link); |
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} |
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} |
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private static LockToken token(boolean created, @Nullable Path p) { |
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return ((p != null) && Files.exists(p)) |
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? new LockToken(created, Optional.of(p)) |
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: new LockToken(created, Optional.empty()); |
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} |
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private static String uniqueLinkPath(File file) { |
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UUID id = UUID.randomUUID(); |
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return file.getAbsolutePath() + "." //$NON-NLS-1$
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+ Long.toHexString(id.getMostSignificantBits()) |
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+ Long.toHexString(id.getLeastSignificantBits()); |
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} |
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} |
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Matthias Sohn
6 years ago