treestate: implement gc

Summary:
Implement gc for treestate. Dirstate writes are protected by wlock. So it's
fine to do a gc inside the write method.

Reviewed By: markbt

Differential Revision: D8394736

fbshipit-source-id: 672087a2c14b855d1ca0449eb5b7d92d65bba418

hgext/treedirstate.py

@@ -733,6 +733,9 @@ def cleanup(ui, repo, debug=None):
                         % (treeid, ", ".join(treesinuse[treeid]))
                     )
 
+    if "treestate" in repo.requirements:
+        repo.dirstate._map._gc()
+
 
 def wrapdirstate(orig, self):
     ds = orig(self)

mercurial/treestate.py

@@ -73,6 +73,9 @@ class treestatemap(object):
     and an offset.
     """
 
+    # Filenames (uuid) that are currently in use. Useful for gc.
+    fileinuse = set()
+
     def __init__(self, ui, vfs, root, importdirstate=None):
         self._filename = None
         self._ui = ui
@@ -251,8 +254,8 @@ class treestatemap(object):
     def setparents(self, p1, p2):
         self._parents = (p1, p2)
 
-    def _read(self):
-        """Read every metadata automatically"""
+    def _parsedirstate(self, filename):
+        """Parse given dirstate metadata file"""
         dirstate = self._vfs.tryread("dirstate")
         f = util.stringio(dirstate)
         p1 = f.read(20) or node.nullid
@@ -276,6 +279,12 @@ class treestatemap(object):
             rootid = 0
             threshold = 0
 
+        return p1, p2, filename, rootid, threshold
+
+    def _read(self):
+        """Read every metadata automatically"""
+        p1, p2, filename, rootid, threshold = self._parsedirstate("dirstate")
+
         self._parents = (p1, p2)
         self._threshold = threshold
         self._rootid = rootid
@@ -308,10 +317,27 @@ class treestatemap(object):
         if filename is None:
             filename = "%s" % uuid.uuid4()
             assert self._filename != filename
+        self.fileinuse.add(filename)
         self._filename = filename
         path = self._vfs.join("treestate", self._filename)
         return path
 
+    def _gc(self):
+        """Remove unreferenced treestate files"""
+        for name in ["dirstate", "undo.dirstate", "undo.backup.dirstate"]:
+            try:
+                _p1, _p2, filename = self._parsedirstate(name)[:3]
+                self.fileinuse.add(filename)
+            except Exception:
+                # dirstate file does not exist, or is in an incompatible
+                # format.
+                pass
+        for name in self._vfs.listdir("treestate"):
+            if name in self.fileinuse:
+                continue
+            self._ui.debug("removing unreferenced treestate/%s\n" % name)
+            self._vfs.tryunlink("treestate/%s" % name)
+
     def write(self, st, now):
         # write .hg/treestate/<uuid>
         metadata = {}
@@ -340,6 +366,7 @@ class treestatemap(object):
             # recalculate threshold
             self._threshold = 0
             rootid = self._tree.saveas(path)
+            self._gc()
         else:
             rootid = self._tree.flush()
 

tests/test-treestate-repack.t

@@ -56,9 +56,11 @@ Auto repack happens when treestate exceeds size threshold
   .
   .
   creating treestate/00000000-0000-0000-0000-000000000002
+  removing unreferenced treestate/00000000-0000-0000-0000-000000000000
   $ hg debugtreestate
   dirstate v2 (using treestate/00000000-0000-0000-0000-000000000002, offset 88, 5 files tracked)
 
 Cleanup removes the leftover files
 
   $ hg debugtreestate cleanup --debug
+  removing unreferenced treestate/00000000-0000-0000-0000-000000000001