diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -16,7 +16,6 @@
 import collections
 import contextlib
 import errno
-import hashlib
 import os
 import re
 import struct
@@ -74,6 +73,7 @@
 )
 from .utils import (
     interfaceutil,
+    storageutil,
     stringutil,
 )
 
@@ -197,33 +197,6 @@
         raise ValueError('unknown revlog index flags')
     return int(int(offset) << 16 | type)
 
-_nullhash = hashlib.sha1(nullid)
-
-def hash(text, p1, p2):
-    """generate a hash from the given text and its parent hashes
-
-    This hash combines both the current file contents and its history
-    in a manner that makes it easy to distinguish nodes with the same
-    content in the revision graph.
-    """
-    # As of now, if one of the parent node is null, p2 is null
-    if p2 == nullid:
-        # deep copy of a hash is faster than creating one
-        s = _nullhash.copy()
-        s.update(p1)
-    else:
-        # none of the parent nodes are nullid
-        if p1 < p2:
-            a = p1
-            b = p2
-        else:
-            a = p2
-            b = p1
-        s = hashlib.sha1(a)
-        s.update(b)
-    s.update(text)
-    return s.digest()
-
 @attr.s(slots=True, frozen=True)
 class _revisioninfo(object):
     """Information about a revision that allows building its fulltext
@@ -1383,7 +1356,7 @@
         returns True if text is different than what is stored.
         """
         p1, p2 = self.parents(node)
-        return hash(text, p1, p2) != node
+        return storageutil.hashrevisionsha1(text, p1, p2) != node
 
     def _cachesegment(self, offset, data):
         """Add a segment to the revlog cache.
@@ -1672,7 +1645,7 @@
         Available as a function so that subclasses can replace the hash
         as needed.
         """
-        return hash(text, p1, p2)
+        return storageutil.hashrevisionsha1(text, p1, p2)
 
     def _processflags(self, text, flags, operation, raw=False):
         """Inspect revision data flags and applies transforms defined by
diff --git a/mercurial/utils/storageutil.py b/mercurial/utils/storageutil.py
new file mode 100644
--- /dev/null
+++ b/mercurial/utils/storageutil.py
@@ -0,0 +1,41 @@
+# storageutil.py - Storage functionality agnostic of backend implementation.
+#
+# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+import hashlib
+
+from ..node import (
+    nullid,
+)
+
+_nullhash = hashlib.sha1(nullid)
+
+def hashrevisionsha1(text, p1, p2):
+    """Compute the SHA-1 for revision data and its parents.
+
+    This hash combines both the current file contents and its history
+    in a manner that makes it easy to distinguish nodes with the same
+    content in the revision graph.
+    """
+    # As of now, if one of the parent node is null, p2 is null
+    if p2 == nullid:
+        # deep copy of a hash is faster than creating one
+        s = _nullhash.copy()
+        s.update(p1)
+    else:
+        # none of the parent nodes are nullid
+        if p1 < p2:
+            a = p1
+            b = p2
+        else:
+            a = p2
+            b = p1
+        s = hashlib.sha1(a)
+        s.update(b)
+    s.update(text)
+    return s.digest()
diff --git a/tests/simplestorerepo.py b/tests/simplestorerepo.py
--- a/tests/simplestorerepo.py
+++ b/tests/simplestorerepo.py
@@ -40,6 +40,7 @@
 )
 from mercurial.utils import (
     interfaceutil,
+    storageutil,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
@@ -285,7 +286,7 @@
     def checkhash(self, text, node, p1=None, p2=None, rev=None):
         if p1 is None and p2 is None:
             p1, p2 = self.parents(node)
-        if node != revlog.hash(text, p1, p2):
+        if node != storageutil.hashrevisionsha1(text, p1, p2):
             raise simplestoreerror(_("integrity check failed on %s") %
                 self._path)
 
@@ -342,7 +343,7 @@
 
         p1, p2 = self.parents(node)
 
-        if revlog.hash(t, p1, p2) == node:
+        if storageutil.hashrevisionsha1(t, p1, p2) == node:
             return False
 
         if self.iscensored(self.rev(node)):
@@ -420,11 +421,11 @@
         validatenode(p2)
 
         if flags:
-            node = node or revlog.hash(text, p1, p2)
+            node = node or storageutil.hashrevisionsha1(text, p1, p2)
 
         rawtext, validatehash = self._processflags(text, flags, 'write')
 
-        node = node or revlog.hash(text, p1, p2)
+        node = node or storageutil.hashrevisionsha1(text, p1, p2)
 
         if node in self._indexbynode:
             return node