Direct mode: Support filesystems like FAT which can change their inodes each time they are mounted.

Annex.hs

@@ -116,6 +116,7 @@ data AnnexState = AnnexState
 	, flags :: M.Map String Bool
 	, fields :: M.Map String String
 	, cleanup :: M.Map String (Annex ())
+	, inodeschanged :: Maybe Bool
 	}
 
 newState :: Git.Repo -> AnnexState
@@ -145,6 +146,7 @@ newState gitrepo = AnnexState
 	, flags = M.empty
 	, fields = M.empty
 	, cleanup = M.empty
+	, inodeschanged = Nothing
 	}
 
 {- Makes an Annex state object for the specified git repo.

Annex/Content.hs

@@ -304,8 +304,8 @@ prepSendAnnex key = withObjectLoc key indirect direct
 	direct (f:fs) = do
 		cache <- recordedInodeCache key
 		-- check that we have a good file
-		ifM (liftIO $ compareInodeCache f cache)
+		ifM (sameInodeCache f cache)
-			( return $ Just (f, liftIO $ compareInodeCache f cache)
+			( return $ Just (f, sameInodeCache f cache)
 			, direct fs
 			)
 
@@ -356,7 +356,7 @@ removeAnnex key = withObjectLoc key remove removedirect
 		cache <- recordedInodeCache key
 		removeInodeCache key
 		mapM_ (resetfile cache) fs
-	resetfile cache f = whenM (liftIO $ compareInodeCache f cache) $ do
+	resetfile cache f = whenM (sameInodeCache f cache) $ do
 		l <- calcGitLink f key
 		top <- fromRepo Git.repoPath
 		cwd <- liftIO getCurrentDirectory

Annex/Content/Direct.hs

@@ -1,6 +1,6 @@
 {- git-annex file content managing for direct mode
  -
- - Copyright 2010,2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2012-2013 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -14,12 +14,13 @@ module Annex.Content.Direct (
 	recordedInodeCache,
 	updateInodeCache,
 	writeInodeCache,
-	compareInodeCache,
+	sameInodeCache,
 	removeInodeCache,
 	toInodeCache,
 ) where
 
 import Common.Annex
+import qualified Annex
 import Annex.Perms
 import qualified Git
 import Utility.TempFile
@@ -94,9 +95,7 @@ normaliseAssociatedFile file = do
  - expected mtime and inode.
  -}
 goodContent :: Key -> FilePath -> Annex Bool
-goodContent key file = do
+goodContent key file = sameInodeCache file =<< recordedInodeCache key
-	old <- recordedInodeCache key
-	liftIO $ compareInodeCache file old
 
 changedFileStatus :: Key -> FileStatus -> Annex Bool
 changedFileStatus key status = do
@@ -128,3 +127,45 @@ removeInodeCache key = withInodeCacheFile key $ \f -> do
 
 withInodeCacheFile :: Key -> (FilePath -> Annex a) -> Annex a
 withInodeCacheFile key a = a =<< inRepo (gitAnnexInodeCache key)
+
+{- Checks if a file's InodeCache matches its current info.
+ -
+ - If the inodes have changed, only the size and mtime are compared.
+ -}
+sameInodeCache :: FilePath -> Maybe InodeCache -> Annex Bool
+sameInodeCache _ Nothing = return False
+sameInodeCache file (Just old) = go =<< liftIO (genInodeCache file)
+  where
+	go Nothing = return False
+	go (Just curr)
+		| curr == old = return True
+		| otherwise = ifM inodesChanged
+			( return $ compareWeak curr old
+			, return False
+			)
+
+{- Some filesystems get new inodes each time they are mounted.
+ - In order to work on such a filesystem, a sentinal file is used to detect
+ - when the inodes have changed. -}
+inodesChanged :: Annex Bool
+inodesChanged = maybe calc return =<< Annex.getState Annex.inodeschanged
+  where
+	calc = do
+		sentinalfile <- fromRepo gitAnnexInodeSentinal
+		sentinalcachefile <- fromRepo gitAnnexInodeSentinalCache
+		scache <- liftIO $ genInodeCache sentinalfile
+		scached <- liftIO $ catchMaybeIO $ readInodeCache <$> readFile sentinalcachefile
+		case (scache, scached) of
+			(Just c1, Just (Just c2)) -> changed $ c1 /= c2
+			_ -> do
+				writesentinal
+				changed True
+	changed v = do
+		Annex.changeState $ \s -> s { Annex.inodeschanged = Just v }
+		return v
+	writesentinal = do
+		sentinalfile <- fromRepo gitAnnexInodeSentinal
+		sentinalcachefile <- fromRepo gitAnnexInodeSentinalCache
+		liftIO $ writeFile sentinalfile ""
+		liftIO $ maybe noop (writeFile sentinalcachefile . showInodeCache)
+			=<< genInodeCache sentinalfile

Annex/Direct.hs

@@ -85,7 +85,7 @@ addDirect file cache = do
 	got Nothing = do
 		showEndFail
 		return False
-	got (Just (key, _)) = ifM (liftIO $ compareInodeCache file $ Just cache)
+	got (Just (key, _)) = ifM (sameInodeCache file $ Just cache)
 		( do
 			stageSymlink file =<< hashSymlink =<< calcGitLink file key
 			writeInodeCache key cache

Locations.hs

@@ -13,6 +13,8 @@ module Locations (
 	gitAnnexLocation,
 	gitAnnexMapping,
 	gitAnnexInodeCache,
+	gitAnnexInodeSentinal,
+	gitAnnexInodeSentinalCache,
 	annexLocations,
 	annexLocation,
 	gitAnnexDir,
@@ -128,6 +130,12 @@ gitAnnexInodeCache key r  = do
 	loc <- gitAnnexLocation key r 
 	return $ loc ++ ".cache"
 
+gitAnnexInodeSentinal :: Git.Repo -> FilePath
+gitAnnexInodeSentinal r = gitAnnexDir r </> "sentinal"
+
+gitAnnexInodeSentinalCache :: Git.Repo -> FilePath
+gitAnnexInodeSentinalCache r = gitAnnexInodeSentinal r ++ ".cache"
+
 {- The annex directory of a repository. -}
 gitAnnexDir :: Git.Repo -> FilePath
 gitAnnexDir r = addTrailingPathSeparator $ Git.localGitDir r </> annexDir

Utility/InodeCache.hs

@@ -13,6 +13,13 @@ import System.Posix.Types
 data InodeCache = InodeCache FileID FileOffset EpochTime
 	deriving (Eq, Show)
 
+{- Weak comparison of the inode caches, comparing the size and mtime, but
+ - not the actual inode.  Useful when inodes have changed, perhaps
+ - due to some filesystems being remounted. -}
+compareWeak :: InodeCache -> InodeCache -> Bool
+compareWeak (InodeCache _ size1 mtime1) (InodeCache _ size2 mtime2) =
+	size1 == size2 && mtime1 == mtime2
+
 showInodeCache :: InodeCache -> String
 showInodeCache (InodeCache inode size mtime) = unwords
 	[ show inode
@@ -42,9 +49,3 @@ toInodeCache s
 		(fileSize s)
 		(modificationTime s)
 	| otherwise = Nothing
-
-{- Compares an inode cache with the current inode of file. -}
-compareInodeCache :: FilePath -> Maybe InodeCache -> IO Bool
-compareInodeCache file old = do
-	curr <- genInodeCache file
-	return $ isJust curr && curr == old

debian/changelog

@@ -8,6 +8,8 @@ git-annex (3.20130217) UNRELEASED; urgency=low
     the main local repository.
   * Android: Bundle now includes openssh.
   * Android: Support ssh connection caching.
+  * Direct mode: Support filesystems like FAT which can change their inodes
+    each time they are mounted.
 
  -- Joey Hess <joeyh@debian.org>  Sun, 17 Feb 2013 16:42:16 -0400