Avoid any access to keys database in v5 mode repositories, which are not supposed to use that database.

Annex/Version.hs

@@ -55,6 +55,9 @@ versionSupportsUnlockedPointers = go <$> getVersion
 versionSupportsAdjustedBranch :: Annex Bool
 versionSupportsAdjustedBranch = versionSupportsUnlockedPointers
 
+versionUsesKeysDatabase :: Annex Bool
+versionUsesKeysDatabase = versionSupportsUnlockedPointers
+
 setVersion :: Version -> Annex ()
 setVersion = setConfig versionField
 

CHANGELOG

@@ -28,6 +28,8 @@ git-annex (6.20160614) UNRELEASED; urgency=medium
   * webapp: Escape unusual characters in ssh hostnames when generating
     mangled hostnames. This allows IPv6 addresses to be used on filesystems
     not supporting : in filenames.
+  * Avoid any access to keys database in v5 mode repositories, which 
+    are not supposed to use that database.
 
  -- Joey Hess <id@joeyh.name>  Mon, 13 Jun 2016 21:52:24 -0400
 

Database/Keys.hs

@@ -27,6 +27,7 @@ import Database.Keys.Handle
 import qualified Database.Queue as H
 import Annex.Locations
 import Annex.Common hiding (delete)
+import Annex.Version (versionUsesKeysDatabase)
 import qualified Annex
 import Annex.Perms
 import Annex.LockFile
@@ -53,9 +54,12 @@ import Database.Esqueleto hiding (Key)
  - Any queued writes will be flushed before the read.
  -}
 runReader :: Monoid v => (SQL.ReadHandle -> Annex v) -> Annex v
-runReader a = do
+runReader a = ifM versionUsesKeysDatabase
-	h <- getDbHandle
+	( do
-	withDbState h go
+		h <- getDbHandle
+		withDbState h go
+	, return mempty
+	)
   where
 	go DbUnavailable = return (mempty, DbUnavailable)
 	go st@(DbOpen qh) = do
@@ -77,7 +81,7 @@ runReaderIO a = runReader (liftIO . a)
  -
  - The database is created if it doesn't exist yet. -}
 runWriter :: (SQL.WriteHandle -> Annex ()) -> Annex ()
-runWriter a = do
+runWriter a = whenM versionUsesKeysDatabase $ do
 	h <- getDbHandle
 	withDbState h go
   where
@@ -146,7 +150,8 @@ openDb createdb _ = catchPermissionDenied permerr $ withExclusiveLock gitAnnexKe
  - data to it.
  -}
 closeDb :: Annex ()
-closeDb = liftIO . closeDbHandle =<< getDbHandle
+closeDb = whenM versionUsesKeysDatabase $
+	liftIO . closeDbHandle =<< getDbHandle
 
 addAssociatedFile :: Key -> TopFilePath -> Annex ()
 addAssociatedFile k f = runWriterIO $ SQL.addAssociatedFile (toIKey k) f

doc/bugs/drop_blows_on_lustre__58___SQLite3_returned_ErrorIO/comment_1_49e8920ad09ae71874686f50f566b77c._comment

@@ -0,0 +1,32 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2016-07-19T15:38:21Z"
+ content="""
+The v6 changes added a sqlite database. Some code will try to query or
+write that database even in v5 mode, although it's meant to give up if the
+database is not available.
+
+So, the easy fix, at least for the drop problem, is to avoid using the keys
+database at all in v5 mode. I've made this change and it will probably fix
+the case you reported.
+
+But, that won't help with v6 repos which need to use that sqlite database.
+And, incremental fsck uses its own sqlite database too. And,
+[[design/caching_database]] plans are to use sqlite databases more broadly
+in the future.
+
+I'm sure that it's not a good idea for git-annex to catch "disk IO error"
+exceptions from the database layer. So, it seems that most any other fix than
+avoiding using the database would need to be made in sqlite or in lustre,
+which it seems don't get along. At a guess, sqlite is trying to use some
+POSIX filesystem functionality, likely related to locking, that lustre does
+not support.
+
+Hmm, what could be done to hack in support for lustre is to 
+move the sqlite databases to a different filesystem. But, accessing the
+same repo from different hosts which have different sqlite databases would
+lead to inconsistent and buggy behavior. And repo setup would need to
+decide where to put the sqlite databases and manually configure that
+location. So this would be very much a caveat empror configuration.
+"""]]