diff --git a/core/Makefile b/core/Makefile
index 22dcee1..07d1c94 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -523,14 +523,14 @@
 $(INSTALLED_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INTERNAL_BOOTIMAGE_FILES) $(VBOOT_SIGNER)
 	$(call pretty,"Target boot image: $@")
 	$(hide) $(MKBOOTIMG) $(INTERNAL_BOOTIMAGE_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $@.unsigned
-	$(VBOOT_SIGNER) $(FUTILITY) $@.unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $@.keyblock $@
+	$(VBOOT_SIGNER) $(FUTILITY) $@.unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_SUBKEY).vbprivk $@.keyblock $@
 	$(hide) $(call assert-max-image-size,$@,$(BOARD_BOOTIMAGE_PARTITION_SIZE))
 
 .PHONY: bootimage-nodeps
 bootimage-nodeps: $(MKBOOTIMG) $(VBOOT_SIGNER)
 	@echo "make $@: ignoring dependencies"
 	$(hide) $(MKBOOTIMG) $(INTERNAL_BOOTIMAGE_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $(INSTALLED_BOOTIMAGE_TARGET).unsigned
-	$(VBOOT_SIGNER) $(FUTILITY) $(INSTALLED_BOOTIMAGE_TARGET).unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $(INSTALLED_BOOTIMAGE_TARGET).keyblock $(INSTALLED_BOOTIMAGE_TARGET)
+	$(VBOOT_SIGNER) $(FUTILITY) $(INSTALLED_BOOTIMAGE_TARGET).unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_SUBKEY).vbprivk $(INSTALLED_BOOTIMAGE_TARGET).keyblock $(INSTALLED_BOOTIMAGE_TARGET)
 	$(hide) $(call assert-max-image-size,$(INSTALLED_BOOTIMAGE_TARGET),$(BOARD_BOOTIMAGE_PARTITION_SIZE))
 
 else # PRODUCT_SUPPORTS_VBOOT != true
@@ -757,6 +757,7 @@
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION),$(hide) echo "vendor_verity_block_device=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "vboot=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "vboot_key=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY)" >> $(1))
+$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "vboot_subkey=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_SUBKEY)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "futility=$(FUTILITY)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "vboot_signer_cmd=$(VBOOT_SIGNER)" >> $(1))
 $(if $(filter true,$(BOARD_BUILD_SYSTEM_ROOT_IMAGE)),\
@@ -893,7 +894,7 @@
   $(if $(filter true,$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_BOOT_SIGNER)),\
     $(BOOT_SIGNER) /recovery $(1) $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VERITY_SIGNING_KEY).pk8 $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VERITY_SIGNING_KEY).x509.pem $(1))
   $(if $(filter true,$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT)), \
-    $(VBOOT_SIGNER) $(FUTILITY) $(1).unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $(1).keyblock $(1))
+    $(VBOOT_SIGNER) $(FUTILITY) $(1).unsigned $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbpubk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_KEY).vbprivk $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VBOOT_SIGNING_SUBKEY).vbprivk $(1).keyblock $(1))
   $(hide) $(call assert-max-image-size,$(1),$(BOARD_RECOVERYIMAGE_PARTITION_SIZE))
   @echo ----- Made recovery image: $(1) --------
 endef
diff --git a/core/product.mk b/core/product.mk
index 4e8bff1..e97cba4 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -104,6 +104,7 @@
     PRODUCT_SYSTEM_PROPERTY_BLACKLIST \
     PRODUCT_SYSTEM_SERVER_JARS \
     PRODUCT_VBOOT_SIGNING_KEY \
+    PRODUCT_VBOOT_SIGNING_SUBKEY \
     PRODUCT_VERITY_SIGNING_KEY \
     PRODUCT_SYSTEM_VERITY_PARTITION \
     PRODUCT_VENDOR_VERITY_PARTITION \
diff --git a/target/product/base.mk b/target/product/base.mk
index 1699156..4c49e86 100644
--- a/target/product/base.mk
+++ b/target/product/base.mk
@@ -111,6 +111,7 @@
     run-as \
     schedtest \
     sdcard \
+    secdiscard \
     services \
     settings \
     sgdisk \
diff --git a/target/product/embedded.mk b/target/product/embedded.mk
index c40de4f..25a8975 100644
--- a/target/product/embedded.mk
+++ b/target/product/embedded.mk
@@ -89,6 +89,7 @@
 
 PRODUCT_COPY_FILES += \
     system/core/rootdir/init.usb.rc:root/init.usb.rc \
+    system/core/rootdir/init.usb.configfs.rc:root/init.usb.configfs.rc \
     system/core/rootdir/init.trace.rc:root/init.trace.rc \
     system/core/rootdir/ueventd.rc:root/ueventd.rc \
     system/core/rootdir/etc/hosts:system/etc/hosts
diff --git a/target/product/vboot.mk b/target/product/vboot.mk
index e4b1144..48a4883 100644
--- a/target/product/vboot.mk
+++ b/target/product/vboot.mk
@@ -22,3 +22,4 @@
 # We expect this file to exist with the suffixes ".vbprivk" and ".vbpupk".
 # TODO: find a proper location for this
 PRODUCT_VBOOT_SIGNING_KEY := external/vboot_reference/tests/devkeys/kernel_data_key
+PRODUCT_VBOOT_SIGNING_SUBKEY := external/vboot_reference/tests/devkeys/kernel_subkey
diff --git a/tools/releasetools/blockimgdiff.py b/tools/releasetools/blockimgdiff.py
index 6ed9ca2..cb6fc85 100644
--- a/tools/releasetools/blockimgdiff.py
+++ b/tools/releasetools/blockimgdiff.py
@@ -16,6 +16,7 @@
 
 from collections import deque, OrderedDict
 from hashlib import sha1
+import common
 import heapq
 import itertools
 import multiprocessing
@@ -105,11 +106,13 @@
     assert not (trim and pad)
 
     partial = len(self.data) % self.blocksize
+    padded = False
     if partial > 0:
       if trim:
         self.data = self.data[:-partial]
       elif pad:
         self.data += '\0' * (self.blocksize - partial)
+        padded = True
       else:
         raise ValueError(("data for DataImage must be multiple of %d bytes "
                           "unless trim or pad is specified") %
@@ -119,14 +122,23 @@
 
     self.total_blocks = len(self.data) / self.blocksize
     self.care_map = RangeSet(data=(0, self.total_blocks))
-    self.clobbered_blocks = RangeSet()
+    # When the last block is padded, we always write the whole block even for
+    # incremental OTAs. Because otherwise the last block may get skipped if
+    # unchanged for an incremental, but would fail the post-install
+    # verification if it has non-zero contents in the padding bytes.
+    # Bug: 23828506
+    if padded:
+      self.clobbered_blocks = RangeSet(
+          data=(self.total_blocks-1, self.total_blocks))
+    else:
+      self.clobbered_blocks = RangeSet()
     self.extended = RangeSet()
 
     zero_blocks = []
     nonzero_blocks = []
     reference = '\0' * self.blocksize
 
-    for i in range(self.total_blocks):
+    for i in range(self.total_blocks-1 if padded else self.total_blocks):
       d = self.data[i*self.blocksize : (i+1)*self.blocksize]
       if d == reference:
         zero_blocks.append(i)
@@ -138,14 +150,18 @@
     self.file_map = {"__ZERO": RangeSet(zero_blocks),
                      "__NONZERO": RangeSet(nonzero_blocks)}
 
+    if self.clobbered_blocks:
+      self.file_map["__COPY"] = self.clobbered_blocks
+
   def ReadRangeSet(self, ranges):
     return [self.data[s*self.blocksize:e*self.blocksize] for (s, e) in ranges]
 
   def TotalSha1(self, include_clobbered_blocks=False):
-    # DataImage always carries empty clobbered_blocks, so
-    # include_clobbered_blocks can be ignored.
-    assert self.clobbered_blocks.size() == 0
-    return sha1(self.data).hexdigest()
+    if not include_clobbered_blocks:
+      ranges = self.care_map.subtract(self.clobbered_blocks)
+      return sha1(self.ReadRangeSet(ranges)).hexdigest()
+    else:
+      return sha1(self.data).hexdigest()
 
 
 class Transfer(object):
@@ -173,6 +189,12 @@
     return (sum(sr.size() for (_, sr) in self.stash_before) -
             sum(sr.size() for (_, sr) in self.use_stash))
 
+  def ConvertToNew(self):
+    assert self.style != "new"
+    self.use_stash = []
+    self.style = "new"
+    self.src_ranges = RangeSet()
+
   def __str__(self):
     return (str(self.id) + ": <" + str(self.src_ranges) + " " + self.style +
             " to " + str(self.tgt_ranges) + ">")
@@ -267,6 +289,10 @@
       self.ReverseBackwardEdges()
       self.ImproveVertexSequence()
 
+    # Ensure the runtime stash size is under the limit.
+    if self.version >= 2 and common.OPTIONS.cache_size is not None:
+      self.ReviseStashSize()
+
     # Double-check our work.
     self.AssertSequenceGood()
 
@@ -286,7 +312,6 @@
     out = []
 
     total = 0
-    performs_read = False
 
     stashes = {}
     stashed_blocks = 0
@@ -398,7 +423,6 @@
         out.append("%s %s\n" % (xf.style, xf.tgt_ranges.to_string_raw()))
         total += tgt_size
       elif xf.style == "move":
-        performs_read = True
         assert xf.tgt_ranges
         assert xf.src_ranges.size() == tgt_size
         if xf.src_ranges != xf.tgt_ranges:
@@ -423,7 +447,6 @@
                 xf.tgt_ranges.to_string_raw(), src_str))
           total += tgt_size
       elif xf.style in ("bsdiff", "imgdiff"):
-        performs_read = True
         assert xf.tgt_ranges
         assert xf.src_ranges
         if self.version == 1:
@@ -460,9 +483,20 @@
       if free_string:
         out.append("".join(free_string))
 
-      # sanity check: abort if we're going to need more than 512 MB if
-      # stash space
-      assert max_stashed_blocks * self.tgt.blocksize < (512 << 20)
+      if self.version >= 2:
+        # Sanity check: abort if we're going to need more stash space than
+        # the allowed size (cache_size * threshold). There are two purposes
+        # of having a threshold here. a) Part of the cache may have been
+        # occupied by some recovery logs. b) It will buy us some time to deal
+        # with the oversize issue.
+        cache_size = common.OPTIONS.cache_size
+        stash_threshold = common.OPTIONS.stash_threshold
+        max_allowed = cache_size * stash_threshold
+        assert max_stashed_blocks * self.tgt.blocksize < max_allowed, \
+               'Stash size %d (%d * %d) exceeds the limit %d (%d * %.2f)' % (
+                   max_stashed_blocks * self.tgt.blocksize, max_stashed_blocks,
+                   self.tgt.blocksize, max_allowed, cache_size,
+                   stash_threshold)
 
     # Zero out extended blocks as a workaround for bug 20881595.
     if self.tgt.extended:
@@ -489,8 +523,81 @@
         f.write(i)
 
     if self.version >= 2:
-      print("max stashed blocks: %d  (%d bytes)\n" % (
-          max_stashed_blocks, max_stashed_blocks * self.tgt.blocksize))
+      max_stashed_size = max_stashed_blocks * self.tgt.blocksize
+      max_allowed = common.OPTIONS.cache_size * common.OPTIONS.stash_threshold
+      print("max stashed blocks: %d  (%d bytes), limit: %d bytes (%.2f%%)\n" % (
+          max_stashed_blocks, max_stashed_size, max_allowed,
+          max_stashed_size * 100.0 / max_allowed))
+
+  def ReviseStashSize(self):
+    print("Revising stash size...")
+    stashes = {}
+
+    # Create the map between a stash and its def/use points. For example, for a
+    # given stash of (idx, sr), stashes[idx] = (sr, def_cmd, use_cmd).
+    for xf in self.transfers:
+      # Command xf defines (stores) all the stashes in stash_before.
+      for idx, sr in xf.stash_before:
+        stashes[idx] = (sr, xf)
+
+      # Record all the stashes command xf uses.
+      for idx, _ in xf.use_stash:
+        stashes[idx] += (xf,)
+
+    # Compute the maximum blocks available for stash based on /cache size and
+    # the threshold.
+    cache_size = common.OPTIONS.cache_size
+    stash_threshold = common.OPTIONS.stash_threshold
+    max_allowed = cache_size * stash_threshold / self.tgt.blocksize
+
+    stashed_blocks = 0
+    new_blocks = 0
+
+    # Now go through all the commands. Compute the required stash size on the
+    # fly. If a command requires excess stash than available, it deletes the
+    # stash by replacing the command that uses the stash with a "new" command
+    # instead.
+    for xf in self.transfers:
+      replaced_cmds = []
+
+      # xf.stash_before generates explicit stash commands.
+      for idx, sr in xf.stash_before:
+        if stashed_blocks + sr.size() > max_allowed:
+          # We cannot stash this one for a later command. Find out the command
+          # that will use this stash and replace the command with "new".
+          use_cmd = stashes[idx][2]
+          replaced_cmds.append(use_cmd)
+          print("%10d  %9s  %s" % (sr.size(), "explicit", use_cmd))
+        else:
+          stashed_blocks += sr.size()
+
+      # xf.use_stash generates free commands.
+      for _, sr in xf.use_stash:
+        stashed_blocks -= sr.size()
+
+      # "move" and "diff" may introduce implicit stashes in BBOTA v3. Prior to
+      # ComputePatches(), they both have the style of "diff".
+      if xf.style == "diff" and self.version >= 3:
+        assert xf.tgt_ranges and xf.src_ranges
+        if xf.src_ranges.overlaps(xf.tgt_ranges):
+          if stashed_blocks + xf.src_ranges.size() > max_allowed:
+            replaced_cmds.append(xf)
+            print("%10d  %9s  %s" % (xf.src_ranges.size(), "implicit", xf))
+
+      # Replace the commands in replaced_cmds with "new"s.
+      for cmd in replaced_cmds:
+        # It no longer uses any commands in "use_stash". Remove the def points
+        # for all those stashes.
+        for idx, sr in cmd.use_stash:
+          def_cmd = stashes[idx][1]
+          assert (idx, sr) in def_cmd.stash_before
+          def_cmd.stash_before.remove((idx, sr))
+          new_blocks += sr.size()
+
+        cmd.ConvertToNew()
+
+    print("  Total %d blocks are packed as new blocks due to insufficient "
+          "cache size." % (new_blocks,))
 
   def ComputePatches(self, prefix):
     print("Reticulating splines...")
@@ -847,6 +954,57 @@
           a.goes_after[b] = size
 
   def FindTransfers(self):
+    """Parse the file_map to generate all the transfers."""
+
+    def AddTransfer(tgt_name, src_name, tgt_ranges, src_ranges, style, by_id,
+                    split=False):
+      """Wrapper function for adding a Transfer().
+
+      For BBOTA v3, we need to stash source blocks for resumable feature.
+      However, with the growth of file size and the shrink of the cache
+      partition source blocks are too large to be stashed. If a file occupies
+      too many blocks (greater than MAX_BLOCKS_PER_DIFF_TRANSFER), we split it
+      into smaller pieces by getting multiple Transfer()s.
+
+      The downside is that after splitting, we can no longer use imgdiff but
+      only bsdiff."""
+
+      MAX_BLOCKS_PER_DIFF_TRANSFER = 1024
+
+      # We care about diff transfers only.
+      if style != "diff" or not split:
+        Transfer(tgt_name, src_name, tgt_ranges, src_ranges, style, by_id)
+        return
+
+      # Change nothing for small files.
+      if (tgt_ranges.size() <= MAX_BLOCKS_PER_DIFF_TRANSFER and
+          src_ranges.size() <= MAX_BLOCKS_PER_DIFF_TRANSFER):
+        Transfer(tgt_name, src_name, tgt_ranges, src_ranges, style, by_id)
+        return
+
+      pieces = 0
+      while (tgt_ranges.size() > MAX_BLOCKS_PER_DIFF_TRANSFER and
+             src_ranges.size() > MAX_BLOCKS_PER_DIFF_TRANSFER):
+        tgt_split_name = "%s-%d" % (tgt_name, pieces)
+        src_split_name = "%s-%d" % (src_name, pieces)
+        tgt_first = tgt_ranges.first(MAX_BLOCKS_PER_DIFF_TRANSFER)
+        src_first = src_ranges.first(MAX_BLOCKS_PER_DIFF_TRANSFER)
+        Transfer(tgt_split_name, src_split_name, tgt_first, src_first, style,
+                 by_id)
+
+        tgt_ranges = tgt_ranges.subtract(tgt_first)
+        src_ranges = src_ranges.subtract(src_first)
+        pieces += 1
+
+      # Handle remaining blocks.
+      if tgt_ranges.size() or src_ranges.size():
+        # Must be both non-empty.
+        assert tgt_ranges.size() and src_ranges.size()
+        tgt_split_name = "%s-%d" % (tgt_name, pieces)
+        src_split_name = "%s-%d" % (src_name, pieces)
+        Transfer(tgt_split_name, src_split_name, tgt_ranges, src_ranges, style,
+                 by_id)
+
     empty = RangeSet()
     for tgt_fn, tgt_ranges in self.tgt.file_map.items():
       if tgt_fn == "__ZERO":
@@ -854,28 +1012,28 @@
         # in any file and that are filled with zeros.  We have a
         # special transfer style for zero blocks.
         src_ranges = self.src.file_map.get("__ZERO", empty)
-        Transfer(tgt_fn, "__ZERO", tgt_ranges, src_ranges,
-                 "zero", self.transfers)
+        AddTransfer(tgt_fn, "__ZERO", tgt_ranges, src_ranges,
+                    "zero", self.transfers)
         continue
 
       elif tgt_fn == "__COPY":
         # "__COPY" domain includes all the blocks not contained in any
         # file and that need to be copied unconditionally to the target.
-        Transfer(tgt_fn, None, tgt_ranges, empty, "new", self.transfers)
+        AddTransfer(tgt_fn, None, tgt_ranges, empty, "new", self.transfers)
         continue
 
       elif tgt_fn in self.src.file_map:
         # Look for an exact pathname match in the source.
-        Transfer(tgt_fn, tgt_fn, tgt_ranges, self.src.file_map[tgt_fn],
-                 "diff", self.transfers)
+        AddTransfer(tgt_fn, tgt_fn, tgt_ranges, self.src.file_map[tgt_fn],
+                    "diff", self.transfers, self.version >= 3)
         continue
 
       b = os.path.basename(tgt_fn)
       if b in self.src_basenames:
         # Look for an exact basename match in the source.
         src_fn = self.src_basenames[b]
-        Transfer(tgt_fn, src_fn, tgt_ranges, self.src.file_map[src_fn],
-                 "diff", self.transfers)
+        AddTransfer(tgt_fn, src_fn, tgt_ranges, self.src.file_map[src_fn],
+                    "diff", self.transfers, self.version >= 3)
         continue
 
       b = re.sub("[0-9]+", "#", b)
@@ -885,11 +1043,11 @@
         # for .so files that contain version numbers in the filename
         # that get bumped.)
         src_fn = self.src_numpatterns[b]
-        Transfer(tgt_fn, src_fn, tgt_ranges, self.src.file_map[src_fn],
-                 "diff", self.transfers)
+        AddTransfer(tgt_fn, src_fn, tgt_ranges, self.src.file_map[src_fn],
+                    "diff", self.transfers, self.version >= 3)
         continue
 
-      Transfer(tgt_fn, None, tgt_ranges, empty, "new", self.transfers)
+      AddTransfer(tgt_fn, None, tgt_ranges, empty, "new", self.transfers)
 
   def AbbreviateSourceNames(self):
     for k in self.src.file_map.keys():
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 99b319d..ebf47cb 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -390,7 +390,9 @@
     img_keyblock = tempfile.NamedTemporaryFile()
     cmd = [info_dict["vboot_signer_cmd"], info_dict["futility"],
            img_unsigned.name, info_dict["vboot_key"] + ".vbpubk",
-           info_dict["vboot_key"] + ".vbprivk", img_keyblock.name,
+           info_dict["vboot_key"] + ".vbprivk",
+           info_dict["vboot_subkey"] + ".vbprivk",
+           img_keyblock.name,
            img.name]
     p = Run(cmd, stdout=subprocess.PIPE)
     p.communicate()
diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index b148fc1..e5a30ad 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -89,6 +89,9 @@
       Specifies the number of worker-threads that will be used when
       generating patches for incremental updates (defaults to 3).
 
+  --stash_threshold <float>
+      Specifies the threshold that will be used to compute the maximum
+      allowed stash size (defaults to 0.8).
 """
 
 import sys
@@ -128,6 +131,9 @@
 OPTIONS.fallback_to_full = True
 OPTIONS.full_radio = False
 OPTIONS.full_bootloader = False
+# Stash size cannot exceed cache_size * threshold.
+OPTIONS.cache_size = None
+OPTIONS.stash_threshold = 0.8
 
 def MostPopularKey(d, default):
   """Given a dict, return the key corresponding to the largest
@@ -1538,6 +1544,12 @@
       OPTIONS.updater_binary = a
     elif o in ("--no_fallback_to_full",):
       OPTIONS.fallback_to_full = False
+    elif o == "--stash_threshold":
+      try:
+        OPTIONS.stash_threshold = float(a)
+      except ValueError:
+        raise ValueError("Cannot parse value %r for option %r - expecting "
+                         "a float" % (a, o))
     else:
       return False
     return True
@@ -1562,6 +1574,7 @@
                                  "oem_settings=",
                                  "verify",
                                  "no_fallback_to_full",
+                                 "stash_threshold=",
                              ], extra_option_handler=option_handler)
 
   if len(args) != 2:
@@ -1619,6 +1632,11 @@
       output_zip = zipfile.ZipFile(temp_zip_file, "w",
                                    compression=zipfile.ZIP_DEFLATED)
 
+    cache_size = OPTIONS.info_dict.get("cache_size", None)
+    if cache_size is None:
+      raise RuntimeError("can't determine the cache partition size")
+    OPTIONS.cache_size = cache_size
+
     if OPTIONS.incremental_source is None:
       WriteFullOTAPackage(input_zip, output_zip)
       if OPTIONS.package_key is None:
diff --git a/tools/releasetools/rangelib.py b/tools/releasetools/rangelib.py
index 1506658..373bbed 100644
--- a/tools/releasetools/rangelib.py
+++ b/tools/releasetools/rangelib.py
@@ -24,6 +24,7 @@
   lots of runs."""
 
   def __init__(self, data=None):
+    # TODO(tbao): monotonic is broken when passing in a tuple.
     self.monotonic = False
     if isinstance(data, str):
       self._parse_internal(data)
@@ -260,6 +261,38 @@
       out = out.union(RangeSet(str(s1) + "-" + str(e1-1)))
     return out
 
+  def first(self, n):
+    """Return the RangeSet that contains at most the first 'n' integers.
+
+    >>> RangeSet("0-9").first(1)
+    <RangeSet("0")>
+    >>> RangeSet("10-19").first(5)
+    <RangeSet("10-14")>
+    >>> RangeSet("10-19").first(15)
+    <RangeSet("10-19")>
+    >>> RangeSet("10-19 30-39").first(3)
+    <RangeSet("10-12")>
+    >>> RangeSet("10-19 30-39").first(15)
+    <RangeSet("10-19 30-34")>
+    >>> RangeSet("10-19 30-39").first(30)
+    <RangeSet("10-19 30-39")>
+    >>> RangeSet("0-9").first(0)
+    <RangeSet("")>
+    """
+
+    if self.size() <= n:
+      return self
+
+    out = []
+    for s, e in self:
+      if e - s >= n:
+        out += (s, s+n)
+        break
+      else:
+        out += (s, e)
+        n -= e - s
+    return RangeSet(data=out)
+
 
 if __name__ == "__main__":
   import doctest