back out incorrect IO interleaving change

Fix regression in last release that crashes when using --all or running
git-annex in a bare repository. May have also affected git-annex unused and
git-annex info.

Reversed the order of the (++) in Annex.Branch.files so --all will stream
lazily still when there are not a bunch of uncommitted journal files.
Added a todo to maybe improve this later.

This commit was sponsored by Trenton Cronholm on Patreon.

Annex/Branch.hs

@@ -34,7 +34,6 @@ import qualified Data.Map as M
 import Data.Function
 import Data.Char
 import Control.Concurrent (threadDelay)
-import System.IO.Unsafe (unsafeInterleaveIO)
 
 import Annex.Common
 import Annex.BranchState
@@ -335,23 +334,16 @@ commitIndex' jl branchref message basemessage retrynum parents = do
 		commitIndex' jl committedref racemessage basemessage retrynum' [committedref]
 
 {- Lists all files on the branch. including ones in the journal
- - that have not been committed yet. There may be duplicates in the list.
- - Streams lazily. -}
+ - that have not been committed yet. There may be duplicates in the list. -}
 files :: Annex [FilePath]
 files = do
 	update
-	withIndex $ do
-		g <- gitRepo
-		withJournalHandle (go g)
-  where
-	go g jh = readDirectory jh >>= \case
-		Nothing -> branchFiles' g
-		Just file
-			| dirCruft file -> go g jh
-			| otherwise -> do
-				let branchfile = fileJournal file
-				rest <- unsafeInterleaveIO (go g jh)
-				return (branchfile:rest)
+	-- ++ forces the content of the first list to be buffered in memory,
+	-- so use getJournalledFilesStale which should be much smaller most
+	-- of the time. branchFiles will stream as the list is consumed.
+	(++)
+		<$> getJournalledFilesStale
+		<*> branchFiles
 
 {- Files in the branch, not including any from journalled changes,
  - and without updating the branch. -}

Annex/Journal.hs

@@ -55,6 +55,16 @@ getJournalFileStale :: FilePath -> Annex (Maybe String)
 getJournalFileStale file = inRepo $ \g -> catchMaybeIO $
 	readFileStrict $ journalFile file g
 
+{- List of existing journal files, but without locking, may miss new ones
+ - just being added, or may have false positives if the journal is staged
+ - as it is run. -}
+getJournalledFilesStale :: Annex [FilePath]
+getJournalledFilesStale = do
+	g <- gitRepo
+	fs <- liftIO $ catchDefaultIO [] $
+		getDirectoryContents $ gitAnnexJournalDir g
+	return $ filter (`notElem` [".", ".."]) $ map fileJournal fs
+
 withJournalHandle :: (DirectoryHandle -> IO a) -> Annex a
 withJournalHandle a = do
 	d <- fromRepo gitAnnexJournalDir

CHANGELOG

@@ -1,3 +1,11 @@
+git-annex (6.20180428) UNRELEASED; urgency=medium
+
+  * Fix regression in last release that crashes when using
+    --all or running git-annex in a bare repository. May have also
+    affected git-annex unused and git-annex info.
+
+ -- Joey Hess <id@joeyh.name>  Tue, 08 May 2018 13:51:37 -0400
+
 git-annex (6.20180427) upstream; urgency=medium
 
   * move: Now takes numcopies configuration, and required content

doc/bugs/regression_-_fails_to_drop_._Exit_code_11_wo_--debug__44___and_1_with_--debug.mdwn

@@ -101,3 +101,5 @@ error: git-annex died of signal 11
 which also resolves with downgrade of git-annex.
 
 [[!meta author=yoh]]
+
+> [[fixed|done]] --[[Joey]]

doc/bugs/regression_-_fails_to_drop_._Exit_code_11_wo_--debug__44___and_1_with_--debug/comment_1_3c2578d17ce519f80aa278a546df29cf._comment

@@ -0,0 +1,24 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2018-05-08T17:09:35Z"
+ content="""
+Neither git rev 6316072f0 nor 86b18966f is present in my git-annex git repo,
+which makes it kind of hard to look at the diff between whatever versions
+of git-annex you're running. Are you building out of a patched git
+repository?
+
+My guess is [[!commit bea0ad220a68138dc0a43d0c86bb2353ecf92d2c]]
+since it involves both directory reading and unsafeInterleaveIO.
+
+Indeed, it looks like that could defer a readDirStream due to
+unsafeInterleaveIO to outside the open/close bracket. And I suppose reading
+from a closed file handle might conceivably segfault.
+
+Looks like that would affect bare repositories, or using --all.
+I don't think it would affect those commands in a non-bare repository.
+Ah, I see youre whereis is indeed in a bare repository, and your drop
+used --all, so my analysis seems right.
+
+Fixed by backing out the problematic part of the commit.
+"""]]

doc/todo/improve_memory_usage_of_--all.mdwn

@@ -0,0 +1,14 @@
+Using --all, or running in a bare repo, as well as
+`git annex unused` and `git annex info` all end up buffering the list of
+all keys that have uncommitted journalled changes in memory.
+This is due to Annex.Branch.files's call to getJournalledFilesStale which
+reads all the files in the directory into a buffer.
+
+Note that the list of keys in the branch *does* stream in, so this
+is only really a problem when using annex.alwayscommit=false to build
+up big git-annex branch commits via the journal.
+
+An attempt at making it stream via unsafeInterleaveIO failed miserably
+and that is not the right approach. This would be a good place to use
+ResourceT, but it might need some changes to the Annex monad to allow
+combining the two. --[[Joey]]