diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3403,8 +3403,6 @@ def grep(ui, repo, pattern, *pats, **opt
     )
 
     getfile = searcher._getfile
-    matches = searcher._matches
-    copies = searcher._copies
 
     uipathfn = scmutil.getuipathfn(repo)
 
@@ -3514,8 +3512,6 @@ def grep(ui, repo, pattern, *pats, **opt
             fm.data(matched=False)
         fm.end()
 
-    skip = searcher._skip
-    revfiles = searcher._revfiles
     found = False
 
     wopts = logcmdutil.walkopts(
@@ -3532,29 +3528,11 @@ def grep(ui, repo, pattern, *pats, **opt
 
     ui.pager(b'grep')
     fm = ui.formatter(b'grep', opts)
-    for ctx in scmutil.walkchangerevs(
-        repo, revs, makefilematcher, searcher._prep
-    ):
-        rev = ctx.rev()
-        parent = ctx.p1().rev()
-        for fn in sorted(revfiles.get(rev, [])):
-            states = matches[rev][fn]
-            copy = copies.get(rev, {}).get(fn)
-            if fn in skip:
-                if copy:
-                    skip.add(copy)
-                continue
-            pstates = matches.get(parent, {}).get(copy or fn, [])
-            if pstates or states:
-                r = display(fm, fn, ctx, pstates, states)
-                found = found or r
-                if r and not diff and not all_files:
-                    searcher.skipfile(fn, rev)
-        del revfiles[rev]
-        # We will keep the matches dict for the duration of the window
-        # clear the matches dict once the window is over
-        if not revfiles:
-            matches.clear()
+    for fn, ctx, pstates, states in searcher.searchfiles(revs, makefilematcher):
+        r = display(fm, fn, ctx, pstates, states)
+        found = found or r
+        if r and not diff and not all_files:
+            searcher.skipfile(fn, ctx.rev())
     fm.end()
 
     return not found
diff --git a/mercurial/grep.py b/mercurial/grep.py
--- a/mercurial/grep.py
+++ b/mercurial/grep.py
@@ -115,6 +115,34 @@ class grepsearcher(object):
         if copy:
             self._skip.add(copy)
 
+    def searchfiles(self, revs, makefilematcher):
+        """Walk files and revisions to yield (fn, ctx, pstates, states)
+        matches
+
+        states is a list of linestate objects. pstates may be empty unless
+        diff is True.
+        """
+        for ctx in scmutil.walkchangerevs(
+            self._repo, revs, makefilematcher, self._prep
+        ):
+            rev = ctx.rev()
+            parent = ctx.p1().rev()
+            for fn in sorted(self._revfiles.get(rev, [])):
+                states = self._matches[rev][fn]
+                copy = self._copies.get(rev, {}).get(fn)
+                if fn in self._skip:
+                    if copy:
+                        self._skip.add(copy)
+                    continue
+                pstates = self._matches.get(parent, {}).get(copy or fn, [])
+                if pstates or states:
+                    yield fn, ctx, pstates, states
+            del self._revfiles[rev]
+            # We will keep the matches dict for the duration of the window
+            # clear the matches dict once the window is over
+            if not self._revfiles:
+                self._matches.clear()
+
     def _grepbody(self, fn, rev, body):
         self._matches[rev].setdefault(fn, [])
         m = self._matches[rev][fn]