fsck for v6 unlocked files

This only adds 1 stat to each file fscked for locked files, so
added overhead is minimal.

For unlocked files it has to access the database to see if a file
is modified.

Command/Fsck.hs

@@ -34,6 +34,7 @@ import Utility.HumanTime
 import Utility.CopyFile
 import Git.FilePath
 import Utility.PID
+import qualified Database.Keys
 
 #ifdef WITH_DATABASE
 import qualified Database.Fsck as FsckDb
@@ -118,16 +119,18 @@ start from inc file key = do
 	go = runFsck inc file key
 
 perform :: Key -> FilePath -> Backend -> NumCopies -> Annex Bool
-perform key file backend numcopies = check
-	-- order matters
-	[ fixLink key file
-	, verifyLocationLog key file
-	, verifyDirectMapping key file
-	, verifyDirectMode key file
-	, checkKeySize key
-	, checkBackend backend key (Just file)
-	, checkKeyNumCopies key (Just file) numcopies
-	]
+perform key file backend numcopies = do
+	keystatus <- getKeyStatus key
+	check
+		-- order matters
+		[ fixLink key file
+		, verifyLocationLog key keystatus file
+		, verifyDirectMapping key file
+		, verifyDirectMode key file
+		, checkKeySize key keystatus
+		, checkBackend backend key keystatus (Just file)
+		, checkKeyNumCopies key (Just file) numcopies
+		]
 
 {- To fsck a remote, the content is retrieved to a tmp file,
  - and checked locally. -}
@@ -183,19 +186,19 @@ startKey inc key numcopies =
 			performKey key backend numcopies
 
 performKey :: Key -> Backend -> NumCopies -> Annex Bool
-performKey key backend numcopies = check
-	[ verifyLocationLog key (key2file key)
-	, checkKeySize key
-	, checkBackend backend key Nothing
-	, checkKeyNumCopies key Nothing numcopies
-	]
+performKey key backend numcopies = do
+	keystatus <- getKeyStatus key
+	check
+		[ verifyLocationLog key keystatus (key2file key)
+		, checkKeySize key keystatus
+		, checkBackend backend key keystatus Nothing
+		, checkKeyNumCopies key Nothing numcopies
+		]
 
 check :: [Annex Bool] -> Annex Bool
 check cs = and <$> sequence cs
 
-{- Checks that the file's link points correctly to the content.
- -
- - In direct mode, there is only a link when the content is not present.
+{- Checks that symlinks points correctly to the annexed content.
  -}
 fixLink :: Key -> FilePath -> Annex Bool
 fixLink key file = do
@@ -214,19 +217,23 @@ fixLink key file = do
 
 {- Checks that the location log reflects the current status of the key,
  - in this repository only. -}
-verifyLocationLog :: Key -> String -> Annex Bool
-verifyLocationLog key desc = do
-	present <- inAnnex key
+verifyLocationLog :: Key -> KeyStatus -> String -> Annex Bool
+verifyLocationLog key keystatus desc = do
+	obj <- calcRepo $ gitAnnexLocation key
+	present <- if isKeyUnlocked keystatus
+		then liftIO (doesFileExist obj)
+		else inAnnex key
 	direct <- isDirect
 	u <- getUUID
 	
-	{- Since we're checking that a key's file is present, throw
+	{- Since we're checking that a key's object file is present, throw
 	 - in a permission fixup here too. -}
-	file <- calcRepo $ gitAnnexLocation key
-	when (present && not direct) $
-		freezeContent file
-	whenM (liftIO $ doesDirectoryExist $ parentDir file) $
-		freezeContentDir file
+	when (present && not direct) $ void $ tryIO $
+		if isKeyUnlocked keystatus
+			then thawContent obj
+			else freezeContent obj
+	whenM (liftIO $ doesDirectoryExist $ parentDir obj) $
+		freezeContentDir obj
 
 	{- In direct mode, modified files will show up as not present,
 	 - but that is expected and not something to do anything about. -}
@@ -288,10 +295,11 @@ verifyDirectMode key file = do
 {- The size of the data for a key is checked against the size encoded in
  - the key's metadata, if available.
  -
- - Not checked in direct mode, because files can be changed directly.
+ - Not checked when a file is unlocked, or in direct mode.
  -}
-checkKeySize :: Key -> Annex Bool
-checkKeySize key = ifM isDirect
+checkKeySize :: Key -> KeyStatus -> Annex Bool
+checkKeySize _ KeyUnlocked = return True
+checkKeySize key KeyLocked = ifM isDirect
 	( return True
 	, do
 		file <- calcRepo $ gitAnnexLocation key
@@ -326,18 +334,26 @@ checkKeySizeOr bad key file = case Types.Key.keySize key of
 			, msg
 			]
 
-{- Runs the backend specific check on a key's content.
+{- Runs the backend specific check on a key's content object.
+ -
+ - When a file is unlocked, it may be a hard link to the object,
+ - thus when the user modifies the file, the object will be modified and
+ - not pass the check, and we don't want to find an error in this case.
+ - So, skip the check if the key is unlocked and modified.
  -
  - In direct mode this is not done if the file has clearly been modified,
  - because modification of direct mode files is allowed. It's still done
  - if the file does not appear modified, to catch disk corruption, etc.
  -}
-checkBackend :: Backend -> Key -> Maybe FilePath -> Annex Bool
-checkBackend backend key mfile = go =<< isDirect
+checkBackend :: Backend -> Key -> KeyStatus -> Maybe FilePath -> Annex Bool
+checkBackend backend key keystatus mfile = go =<< isDirect
   where
 	go False = do
 		content <- calcRepo $ gitAnnexLocation key
-		checkBackendOr badContent backend key content
+		ifM (pure (isKeyUnlocked keystatus) <&&> (not <$> isUnmodified key content))
+			( nocheck
+			, checkBackendOr badContent backend key content
+			)
 	go True = maybe nocheck checkdirect mfile
 	checkdirect file = ifM (goodContent key file)
 		( checkBackendOr' (badContentDirect file) backend key file
@@ -582,3 +598,16 @@ withFsckDb (StartIncremental h) a = a h
 withFsckDb NonIncremental _ = noop
 withFsckDb (ScheduleIncremental _ _ i) a = withFsckDb i a
 #endif
+
+data KeyStatus = KeyLocked | KeyUnlocked
+
+isKeyUnlocked :: KeyStatus -> Bool
+isKeyUnlocked KeyUnlocked = True
+isKeyUnlocked KeyLocked = False
+
+getKeyStatus :: Key -> Annex KeyStatus
+getKeyStatus key = do
+	obj <- calcRepo $ gitAnnexLocation key
+	unlocked <- ((> 1) . linkCount <$> liftIO (getFileStatus obj))
+		<&&> (not . null <$> Database.Keys.getAssociatedFiles key)
+	return $ if unlocked then KeyUnlocked else KeyLocked