Reduce lock scope in FSDirectory.DeleteFile, #1428

src/Lucene.Net/Store/FSDirectory.cs

@@ -317,10 +317,6 @@ public override void DeleteFile(string name)
             EnsureOpen();
             string file = Path.Combine(m_directory.FullName, name);
 
-            // LUCENENET Specific: See remarks for m_staleFiles field.
-            UninterruptableMonitor.Enter(m_syncLock);
-            try
-            {
                 // LUCENENET specific: We need to explicitly throw when the file has already been deleted,
                 // since FileInfo doesn't do that for us.
                 // (An enhancement carried over from Lucene 8.2.0)
@@ -329,6 +325,13 @@ public override void DeleteFile(string name)
                     throw new FileNotFoundException("Cannot delete " + file + " because it doesn't exist.");
                 }
 
+            // LUCENENET specific: Do NOT hold m_syncLock while deleting. On a network share (SMB),
+            // File.Delete can block for a long time (e.g. waiting for the server to break an
+            // oplock/lease on a file this client still has open). Holding m_syncLock here would
+            // block every concurrent Sync() and IndexOutput.Dispose() on this directory behind
+            // a single stalled delete, freezing the whole writer. Only the m_staleFiles
+            // bookkeeping below needs the lock (see remarks for the m_staleFiles field);
+            // upstream Java likewise performs the delete without any directory-wide lock.
                 try
                 {
                     File.Delete(file);
@@ -342,6 +345,9 @@ public override void DeleteFile(string name)
                     throw new IOException("Cannot delete " + file, e);
                 }
 
+            UninterruptableMonitor.Enter(m_syncLock);
+            try
+            {
                 m_staleFiles.Remove(name);
             }
             finally

src/Lucene.Net/Store/MMapDirectory.cs

@@ -194,7 +194,13 @@ public override IndexInput OpenInput(string name, IOContext context)
             EnsureOpen();
             EnsureCanRead(name); // LUCENENET-specific: backported call site from Lucene 6.0.0
             var file = Path.Combine(Directory.FullName, name); // LUCENENET specific: changed to use string file name instead of allocating a FileInfo (#832)
-            var fc = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
+            // LUCENENET specific: Add FileShare.Delete (a deliberate divergence from upstream Java's RandomAccessFile,
+            // which omits it) to match SimpleFSDirectory, NIOFSDirectory and our other handles, giving Windows the same
+            // delete-while-open semantics POSIX already provides so index files can be deleted while a read handle is
+            // open (#1283). Without it, a pending delete of a still-mapped file on an SMB share can block inside
+            // File.Delete while the server waits for this client's lease break, which cannot complete while mapped
+            // views are active.
+            var fc = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
             return new MMapIndexInput(this, "MMapIndexInput(path=\"" + file + "\")", fc);
         }