diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index bbc5b72..9bdc14a 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -87,6 +87,7 @@ module Mongo
       @db, @name  = db, name
       @connection = @db.connection
       @logger     = @connection.logger
+      @log_duration = @connection.log_duration
       @cache_time = @db.cache_time
       @cache = Hash.new(0)
       unless pk_factory
@@ -264,8 +265,8 @@ module Mongo
     # @return [OrderedHash, Nil]
     #   a single document or nil if no result is found.
     #
-    # @param [Hash, ObjectId, Nil] spec_or_object_id a hash specifying elements 
-    #   which must be present for a document to be included in the result set or an 
+    # @param [Hash, ObjectId, Nil] spec_or_object_id a hash specifying elements
+    #   which must be present for a document to be included in the result set or an
     #   instance of ObjectId to be used as the value for an _id query.
     #   If nil, an empty selector, {}, will be used.
     #
@@ -413,7 +414,7 @@ module Mongo
     # @option opts [Boolean] :upsert (+false+) if true, performs an upsert (update or insert)
     # @option opts [Boolean] :multi (+false+) update all documents matching the selector, as opposed to
     #   just the first matching document. Note: only works in MongoDB 1.1.3 or later.
-    # @option opts [Boolean] :safe (+false+) 
+    # @option opts [Boolean] :safe (+false+)
     #   If true, check that the save succeeded. OperationFailure
     #   will be raised on an error. Note that a safe check requires an extra
     #   round-trip to the database. Safe options provided here will override any safe
@@ -906,12 +907,12 @@ module Mongo
           if [Mongo::ASCENDING, Mongo::DESCENDING, Mongo::GEO2D, Mongo::GEOHAYSTACK].include?(f[1])
             field_spec[f[0].to_s] = f[1]
           else
-            raise MongoArgumentError, "Invalid index field #{f[1].inspect}; " + 
+            raise MongoArgumentError, "Invalid index field #{f[1].inspect}; " +
               "should be one of Mongo::ASCENDING (1), Mongo::DESCENDING (-1) or Mongo::GEO2D ('2d')."
           end
         end
       else
-        raise MongoArgumentError, "Invalid index specification #{spec.inspect}; " + 
+        raise MongoArgumentError, "Invalid index specification #{spec.inspect}; " +
           "should be either a string, symbol, or an array of arrays."
       end
       field_spec
diff --git a/lib/mongo/connection.rb b/lib/mongo/connection.rb
index b338a1e..a6a3291 100644
--- a/lib/mongo/connection.rb
+++ b/lib/mongo/connection.rb
@@ -36,7 +36,7 @@ module Mongo
 
     mongo_thread_local_accessor :connections
 
-    attr_reader :logger, :size, :auths, :primary, :safe, :host_to_try,
+    attr_reader :logger, :log_duration, :size, :auths, :primary, :safe, :host_to_try,
       :pool_size, :connect_timeout, :pool_timeout,
       :primary_pool, :socket_class, :op_timeout
 
@@ -63,6 +63,8 @@ module Mongo
     #   to a single, slave node.
     # @option opts [Logger, #debug] :logger (nil) A Logger instance for debugging driver ops. Note that
     #   logging negatively impacts performance; therefore, it should not be used for high-performance apps.
+    # @option opts [Boolean, #debug] :log_duration (nil) A boolean to say if you want see information about log_duration on logger
+    #   like logging, log_duration negatively impacts performance; therefore, it should not be used for high-performance apps.
     # @option opts [Integer] :pool_size (1) The maximum number of socket self.connections allowed per
     #   connection pool. Note: this setting is relevant only for multi-threaded applications.
     # @option opts [Float] :pool_timeout (5.0) When all of the self.connections a pool are checked out,
@@ -348,7 +350,7 @@ module Mongo
       self["admin"].command(oh)
     end
 
-    # Checks if a server is alive. This command will return immediately 
+    # Checks if a server is alive. This command will return immediately
     # even if the server is in a lock.
     #
     # @return [Hash]
@@ -383,7 +385,7 @@ module Mongo
       Thread.current[:socket_map] ||= {}
       Thread.current[:socket_map][self] ||= {}
       Thread.current[:socket_map][self][:writer] ||= checkout_writer
-      Thread.current[:socket_map][self][:reader] = 
+      Thread.current[:socket_map][self][:reader] =
         Thread.current[:socket_map][self][:writer]
     end
 
@@ -568,6 +570,7 @@ module Mongo
 
       if @logger
         write_logging_startup_message
+        @log_duration = opts[:log_duration] || false
       end
 
       should_connect = opts.fetch(:connect, true)
diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index 452913d..9579562 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -43,6 +43,7 @@ module Mongo
       @collection = collection
       @connection = @db.connection
       @logger     = @connection.logger
+      @log_duration = @connection.log_duration
 
       # Query selector
       @selector   = opts[:selector] || {}
@@ -199,7 +200,7 @@ module Mongo
     # This method overrides any sort order specified in the Collection#find
     # method, and only the last sort applied has an effect.
     #
-    # @param [Symbol, Array] key_or_list either 1) a key to sort by or 2) 
+    # @param [Symbol, Array] key_or_list either 1) a key to sort by or 2)
     #   an array of [key, direction] pairs to sort by. Direction should
     #   be specified as Mongo::ASCENDING (or :ascending / :asc) or Mongo::DESCENDING (or :descending / :desc)
     #
diff --git a/lib/mongo/db.rb b/lib/mongo/db.rb
index f5613f5..72f0e8d 100644
--- a/lib/mongo/db.rb
+++ b/lib/mongo/db.rb
@@ -173,12 +173,15 @@ module Mongo
     #
     # @param [String] username
     # @param [String] password
+    # @param [Boolean] read_only
+    #   Create a read-only user.
     #
     # @return [Hash] an object representing the user.
-    def add_user(username, password)
+    def add_user(username, password, read_only = false)
       users = self[SYSTEM_USER_COLLECTION]
       user  = users.find_one({:user => username}) || {:user => username}
       user['pwd'] = Mongo::Support.hash_password(username, password)
+      user['readOnly'] = true if read_only;
       users.save(user)
       return user
     end
diff --git a/lib/mongo/gridfs/grid_file_system.rb b/lib/mongo/gridfs/grid_file_system.rb
index 3addfaa..c15c1fe 100644
--- a/lib/mongo/gridfs/grid_file_system.rb
+++ b/lib/mongo/gridfs/grid_file_system.rb
@@ -71,6 +71,9 @@ module Mongo
     #  GridFileSystem#delete.
     # @option opts [Boolean] :safe (false) When safe mode is enabled, the chunks sent to the server
     #   will be validated using an md5 hash. If validation fails, an exception will be raised.
+    # @option opts [Integer] :versions (false) deletes all versions which exceed the number specified to 
+    #   retain ordered by uploadDate. This option only works in 'w' mode. Certain precautions must be taken when 
+    #   deleting GridFS files. See the notes under GridFileSystem#delete.
     #
     # @example
     #
@@ -97,7 +100,12 @@ module Mongo
     def open(filename, mode, opts={})
       opts = opts.dup
       opts.merge!(default_grid_io_opts(filename))
-      del  = opts.delete(:delete_old) && mode == 'w'
+      if mode == 'w'
+        versions = opts.delete(:versions)
+        if opts.delete(:delete_old) || (versions && versions < 1)
+          versions = 1
+        end
+      end
       file = GridIO.new(@files, @chunks, filename, mode, opts)
       return file unless block_given?
       result = nil
@@ -105,9 +113,9 @@ module Mongo
         result = yield file
       ensure
         id = file.close
-        if del
+        if versions
           self.delete do
-            @files.find({'filename' => filename, '_id' => {'$ne' => id}}, :fields => ['_id'])
+            @files.find({'filename' => filename, '_id' => {'$ne' => id}}, :fields => ['_id'], :sort => ['uploadDate', -1], :skip => (versions -1))
           end
         end
       end
diff --git a/lib/mongo/util/logging.rb b/lib/mongo/util/logging.rb
index 48a22a3..b6f303d 100644
--- a/lib/mongo/util/logging.rb
+++ b/lib/mongo/util/logging.rb
@@ -25,14 +25,15 @@ module Mongo
 
     # Execute the block and log the operation described by name and payload.
     def instrument(name, payload = {}, &blk)
+      time_elapse = @log_duration ? Time.now : nil
       res = yield
-      log_operation(name, payload)
+      log_operation(name, payload, time_elapse)
       res
     end
 
     protected
 
-    def log_operation(name, payload)
+    def log_operation(name, payload, time_elapse=nil)
       @logger ||= nil
       return unless @logger
       msg = "#{payload[:database]}['#{payload[:collection]}'].#{name}("
@@ -40,7 +41,11 @@ module Mongo
       msg += ".skip(#{payload[:skip]})"  if payload[:skip]
       msg += ".limit(#{payload[:limit]})"  if payload[:limit]
       msg += ".sort(#{payload[:order]})"  if payload[:order]
-      @logger.debug "MONGODB #{msg}"
+      if time_elapse
+        @logger.debug "MONGODB (#{Time.now - time_elapse}s) #{msg}"
+      else
+        @logger.debug "MONGODB #{msg}"
+      end
     end
 
   end
diff --git a/test/auxillary/authentication_test.rb b/test/auxillary/authentication_test.rb
index 83d33b4..a744d1e 100644
--- a/test/auxillary/authentication_test.rb
+++ b/test/auxillary/authentication_test.rb
@@ -26,6 +26,7 @@ class AuthenticationTest < Test::Unit::TestCase
     @admin.authenticate('bob', 'secret')
     @db1.add_user('user1', 'secret')
     @db2.add_user('user2', 'secret')
+    @db2.add_user('userRO', 'secret', true) # read-only
     @admin.logout
 
     assert_raise Mongo::OperationFailure do
@@ -53,6 +54,7 @@ class AuthenticationTest < Test::Unit::TestCase
 
     assert @db1['stuff'].insert({:a => 2}, :safe => true)
     assert @db2['stuff'].insert({:a => 2}, :safe => true)
+    assert @db2['stuff'].find(:safe => true)
 
     @db1.logout
     assert_raise Mongo::OperationFailure do
@@ -63,6 +65,12 @@ class AuthenticationTest < Test::Unit::TestCase
     assert_raise Mongo::OperationFailure do
       assert @db2['stuff'].insert({:a => 2}, :safe => true)
     end
+
+    @db2.authenticate('userRO', 'secret')
+    assert @db2['stuff'].find(:safe => true)
+    assert_raise Mongo::OperationFailure do
+      assert @db2['stuff'].insert({:a => 2}, :safe => true)
+    end
   end
 
 end
diff --git a/test/connection_test.rb b/test/connection_test.rb
index 3c1f4f3..8a64357 100644
--- a/test/connection_test.rb
+++ b/test/connection_test.rb
@@ -137,6 +137,15 @@ class TestConnection < Test::Unit::TestCase
     assert output.string.include?("admin['$cmd'].find")
   end
 
+  def test_logging_duration
+    output = StringIO.new
+    logger = Logger.new(output)
+    logger.level = Logger::DEBUG
+    connection = standard_connection(:logger => logger, :log_duration => true).db(MONGO_TEST_DB)
+    assert output.string.index(/\(0.\d+s\)/)
+    assert output.string.include?("admin['$cmd'].find")
+  end
+
   def test_connection_logger
     output = StringIO.new
     logger = Logger.new(output)
@@ -148,6 +157,21 @@ class TestConnection < Test::Unit::TestCase
     assert output.string.include?('testing')
   end
 
+  def test_connection_log_duration_with_logger
+    output = StringIO.new
+    logger = Logger.new(output)
+    logger.level = Logger::DEBUG
+    connection = standard_connection(:logger => logger, :log_duration => true)
+    assert logger, connection.logger
+    assert connection.log_duration
+  end
+
+  def test_connection_log_duration_without_logger
+    connection = standard_connection(:log_duration => true)
+    assert_nil connection.logger
+    assert !connection.log_duration
+  end
+
   def test_drop_database
     db = @conn.db('ruby-mongo-will-be-deleted')
     coll = db.collection('temp')
diff --git a/test/db_test.rb b/test/db_test.rb
index 910d2c8..c14dd39 100644
--- a/test/db_test.rb
+++ b/test/db_test.rb
@@ -151,6 +151,13 @@ class DBTest < Test::Unit::TestCase
     @@db.remove_user('foo:bar')
   end
 
+  def test_authenticate_read_only
+    @@db.add_user('joebob', 'user', true) # read-only user
+    assert @@db.authenticate('joebob', 'user')
+    @@db.logout
+    @@db.remove_user('joebob')
+  end
+
   def test_authenticate_with_connection_uri
     @@db.add_user('spongebob', 'squarepants')
     assert Mongo::Connection.from_uri("mongodb://spongebob:squarepants@#{host_port}/#{@@db.name}")
diff --git a/test/grid_file_system_test.rb b/test/grid_file_system_test.rb
index bac67f4..0cae6b0 100644
--- a/test/grid_file_system_test.rb
+++ b/test/grid_file_system_test.rb
@@ -165,6 +165,18 @@ class GridFileSystemTest < Test::Unit::TestCase
            assert_equal 0, @db['fs.chunks'].find({'files_id' => {'$in' => @ids}}).count
          end
 
+         should "delete all versions which exceed the number of versions to keep specified by the option :versions" do
+           @versions = 1 + rand(4-1)
+           @grid.open('sample', 'w', :versions => @versions) do |f|
+             f.write @new_data
+           end
+           @new_ids = @db['fs.files'].find({'filename' => 'sample'}).map {|file| file['_id']}
+           assert_equal @versions, @new_ids.length
+           id = @new_ids.first
+           assert !@ids.include?(id)
+           assert_equal @versions, @db['fs.files'].find({'filename' => 'sample'}).count
+         end
+         
          should "delete old versions on write with :delete_old is passed in" do
            @grid.open('sample', 'w', :delete_old => true) do |f|
              f.write @new_data