HDFS-12325. SFTPFileSystem operations should restore cwd. Contributed by Chen Liang.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/sftp/SFTPFileSystem.java

@@ -326,8 +326,10 @@ public class SFTPFileSystem extends FileSystem {
         String parentDir = parent.toUri().getPath();
         boolean succeeded = true;
         try {
+          final String previousCwd = client.pwd();
           client.cd(parentDir);
           client.mkdir(pathName);
+          client.cd(previousCwd);
         } catch (SftpException e) {
           throw new IOException(String.format(E_MAKE_DIR_FORPATH, pathName,
               parentDir));
@@ -474,8 +476,10 @@ public class SFTPFileSystem extends FileSystem {
     }
     boolean renamed = true;
     try {
+      final String previousCwd = channel.pwd();
       channel.cd("/");
       channel.rename(src.toUri().getPath(), dst.toUri().getPath());
+      channel.cd(previousCwd);
     } catch (SftpException e) {
       renamed = false;
     }
@@ -558,8 +562,10 @@ public class SFTPFileSystem extends FileSystem {
     }
     OutputStream os;
     try {
+      final String previousCwd = client.pwd();
       client.cd(parent.toUri().getPath());
       os = client.put(f.getName());
+      client.cd(previousCwd);
     } catch (SftpException e) {
       throw new IOException(e);
     }