fix Annex.repoSize sharing between threads

Annex.hs

@@ -132,6 +132,7 @@ data AnnexRead = AnnexRead
 	, forcenumcopies :: Maybe NumCopies
 	, forcemincopies :: Maybe MinCopies
 	, forcebackend :: Maybe String
+	, reposizes :: MVar (Maybe (M.Map UUID RepoSize))
 	, rebalance :: Bool
 	, useragent :: Maybe String
 	, desktopnotify :: DesktopNotify
@@ -149,6 +150,7 @@ newAnnexRead c = do
 	tp <- newTransferrerPool
 	cm <- newTMVarIO M.empty
 	cc <- newTMVarIO (CredentialCache M.empty)
+	rs <- newMVar Nothing
 	return $ AnnexRead
 		{ branchstate = bs
 		, activekeys = emptyactivekeys
@@ -166,6 +168,7 @@ newAnnexRead c = do
 		, forcebackend = Nothing
 		, forcenumcopies = Nothing
 		, forcemincopies = Nothing
+		, reposizes = rs
 		, rebalance = False
 		, useragent = Nothing
 		, desktopnotify = mempty
@@ -202,7 +205,6 @@ data AnnexState = AnnexState
 	, remoteconfigmap :: Maybe (M.Map UUID RemoteConfig)
 	, clusters :: Maybe (Annex Clusters)
 	, maxsizes :: Maybe (M.Map UUID MaxSize)
-	, reposizes :: Maybe (M.Map UUID RepoSize)
 	, forcetrust :: TrustMap
 	, trustmap :: Maybe TrustMap
 	, groupmap :: Maybe GroupMap
@@ -258,7 +260,6 @@ newAnnexState c r = do
 		, remoteconfigmap = Nothing
 		, clusters = Nothing
 		, maxsizes = Nothing
-		, reposizes = Nothing
 		, forcetrust = M.empty
 		, trustmap = Nothing
 		, groupmap = Nothing

Annex/RepoSize.hs

@@ -5,7 +5,7 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE OverloadedStrings, BangPatterns #-}
 
 module Annex.RepoSize (
 	getRepoSizes,
@@ -15,28 +15,35 @@ import Annex.Common
 import Annex.RepoSize.LiveUpdate
 import qualified Annex
 import Annex.Branch (UnmergedBranches(..), getBranch)
-import Annex.Journal (lockJournal)
 import Types.RepoSize
 import qualified Database.RepoSize as Db
 import Logs.Location
 import Logs.UUID
 import Git.Types (Sha)
 
+import Control.Concurrent
 import qualified Data.Map.Strict as M
 
 {- Gets the repo size map. Cached for speed. -}
 getRepoSizes :: Annex (M.Map UUID RepoSize)
-getRepoSizes = maybe calcRepoSizes return =<< Annex.getState Annex.reposizes
+getRepoSizes = do
+	rsv <- Annex.getRead Annex.reposizes
+	liftIO (takeMVar rsv) >>= \case
+		Just sizemap -> do
+			liftIO $ putMVar rsv (Just sizemap)
+			return sizemap
+		Nothing -> calcRepoSizes rsv
 
-{- Sets Annex.reposizes with current information from the git-annex
- - branch, supplimented with journalled but not yet committed information.
- -
- - This should only be called when Annex.reposizes = Nothing.
+{- Fills an empty Annex.reposizes MVar with current information
+ - from the git-annex branch, supplimented with journalled but
+ - not yet committed information.
  -}
-calcRepoSizes :: Annex (M.Map UUID RepoSize)
-calcRepoSizes = bracket Db.openDb Db.closeDb $ \h -> do
+calcRepoSizes :: MVar (Maybe (M.Map UUID RepoSize)) -> Annex (M.Map UUID RepoSize)
+calcRepoSizes rsv = bracket setup cleanup $ \h -> go h `onException` failed
+  where
+	go h = do
 		(oldsizemap, moldbranchsha) <- liftIO $ Db.getRepoSizes h
-	case moldbranchsha of
+		!sizemap <- case moldbranchsha of
 			Nothing -> calculatefromscratch h
 			Just oldbranchsha -> do
 				currbranchsha <- getBranch
@@ -46,13 +53,23 @@ calcRepoSizes = bracket Db.openDb Db.closeDb $ \h -> do
 						-- XXX todo incremental update by diffing
 						-- from old to new branch.
 						calculatefromscratch h
-  where
+		liftIO $ putMVar rsv (Just sizemap)
+		return sizemap
+	
 	calculatefromscratch h = do
 		showSideAction "calculating repository sizes"
 		(sizemap, branchsha) <- calcBranchRepoSizes
 		liftIO $ Db.setRepoSizes h sizemap branchsha
 		calcJournalledRepoSizes sizemap branchsha
 	
+	setup = Db.openDb
+
+	cleanup = Db.closeDb
+
+	failed = do
+		liftIO $ putMVar rsv (Just M.empty)
+		return M.empty
+
 {- Sum up the sizes of all keys in all repositories, from the information
  - in the git-annex branch, but not the journal. Retuns the sha of the
  - branch commit that was used.
@@ -77,19 +94,13 @@ calcBranchRepoSizes = do
 
 {- Given the RepoSizes calculated from the git-annex branch, updates it with
  - data from journalled location logs.
- - 
- - This should only be called when Annex.reposizes = Nothing.
   -}
-calcJournalledRepoSizes :: M.Map UUID RepoSize -> Sha -> Annex (M.Map UUID RepoSize)
-calcJournalledRepoSizes startmap branchsha = lockJournal $ \_jl -> do
-	sizemap <- overLocationLogsJournal startmap branchsha accumsizes
-	-- Set while the journal is still locked. Since Annex.reposizes
-	-- was Nothing until this point, any other thread that might be
-	-- journalling a location log change at the same time will
-	-- be blocked from running updateRepoSize concurrently with this.
-	Annex.changeState $ \st -> st
-			{ Annex.reposizes = Just sizemap }
-	return sizemap
+calcJournalledRepoSizes
+	:: M.Map UUID RepoSize
+	-> Sha 
+	-> Annex (M.Map UUID RepoSize)
+calcJournalledRepoSizes startmap branchsha =
+	overLocationLogsJournal startmap branchsha accumsizes
   where
 	accumsizes k (newlocs, removedlocs) m = return $
 		let m' = foldl' (flip $ M.alter $ addKeyRepoSize k) m newlocs

Annex/RepoSize/LiveUpdate.hs

@@ -14,17 +14,19 @@ import qualified Annex
 import Types.RepoSize
 import Logs.Presence.Pure
 
+import Control.Concurrent
 import qualified Data.Map.Strict as M
 
 updateRepoSize :: UUID -> Key -> LogStatus -> Annex ()
-updateRepoSize u k s = Annex.getState Annex.reposizes >>= \case
-	Nothing -> noop
+updateRepoSize u k s = do
+	rsv <- Annex.getRead Annex.reposizes
+	liftIO (takeMVar rsv) >>= \case
+		Nothing -> liftIO (putMVar rsv Nothing)
 		Just sizemap -> do
 			let !sizemap' = M.adjust 
 				(fromMaybe (RepoSize 0) . f k . Just)
 				u sizemap
-		Annex.changeState $ \st -> st
-			{ Annex.reposizes = Just sizemap' }
+			liftIO $ putMVar rsv (Just sizemap')
   where
 	f = case s of
 		InfoPresent -> addKeyRepoSize

doc/todo/git-annex_proxies.mdwn

@@ -39,10 +39,6 @@ Planned schedule of work:
     Note ideas in above todo about doing this at git-annex branch merge
     time to reuse the git diff done there.
 
-  * Annex.reposizes is not shared amoung threads, so duplicate work
-    to populate it, and threads won't learn about changes made by other
-    threads.
-
   * What if 2 concurrent threads are considering sending two different
     keys to a repo at the same time. It can hold either but not both.
     It should avoid sending both in this situation. (Also discussed in