diff options
| author |  Joey Hess <joeyh@joeyh.name> | 2015-02-17 13:04:22 -0400 |
|---|---|---|
| committer | Joey Hess <joeyh@joeyh.name> | 2015-02-17 13:30:24 -0400 |
| commit | c18aca6a6a1673d17467e25eb5c900f824c8231c (patch) | |
| tree | 0ef32f822433fc6a6306db0b31640588224e19e8 /Database | |
| parent | d14b4c2a607409fbec81fedd2cc89ee77ba6a62e (diff) | |
avoid crash when starting fsck --incremental when one is already running
Turns out sqlite does not like having its database deleted out from
underneath it. It might suffice to empty the table, but I would rather
start each fsck over with a new database, so I added a lock file, and
running incremental fscks use a shared lock.
This leaves one concurrency bug left; running two concurrent fsck --more
will lead to: "SQLite3 returned ErrorBusy while attempting to perform step."
and one or both will fail. This is a concurrent writers problem.
Diffstat (limited to 'Database')
| -rw-r--r-- | Database/Fsck.hs | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/Database/Fsck.hs b/Database/Fsck.hs index a137cba8e..a42988205 100644 --- a/Database/Fsck.hs +++ b/Database/Fsck.hs @@ -11,8 +11,8 @@ module Database.Fsck ( newPass, openDb, + closeDb, H.commitDb, - H.closeDb, H.DbHandle, addDb, inDb, @@ -26,6 +26,7 @@ import Utility.Directory import Annex import Types.Key import Annex.Perms +import Annex.LockFile import Database.Persist.TH import Database.Esqueleto hiding (Key) @@ -33,6 +34,8 @@ import Control.Monad import Control.Monad.IfElse import Control.Monad.IO.Class (liftIO) import System.Directory +import Data.Maybe +import Control.Applicative {- Each key stored in the database has already been fscked as part - of the latest incremental fsck pass. -} @@ -42,9 +45,16 @@ Fscked UniqueKey key |] -{- The database is removed when starting a new incremental fsck pass. -} -newPass :: Annex () -newPass = liftIO. nukeFile =<< fromRepo gitAnnexFsckDb +{- The database is removed when starting a new incremental fsck pass. + - + - This may fail, if other fsck processes are currently running using the + - database. Removing the database in that situation would lead to crashes + - or undefined behavior. + -} +newPass :: Annex Bool +newPass = isJust <$> tryExclusiveLock gitAnnexFsckDbLock go + where + go = liftIO. nukeFile =<< fromRepo gitAnnexFsckDb {- Opens the database, creating it atomically if it doesn't exist yet. -} openDb :: Annex H.DbHandle @@ -58,8 +68,14 @@ openDb = do liftIO $ H.closeDb h setAnnexFilePerm newdb liftIO $ renameFile newdb db + lockFileShared =<< fromRepo gitAnnexFsckDbLock liftIO $ H.openDb db +closeDb :: H.DbHandle -> Annex () +closeDb h = do + liftIO $ H.closeDb h + unlockFile =<< fromRepo gitAnnexFsckDbLock + addDb :: H.DbHandle -> Key -> IO () addDb h = void . H.runDb' h commitPolicy . insert . Fscked . toSKey |