git-annex/Command/Migrate.hs
Joey Hess d5ee5fef65
fsck: Detect situations where annex.thin has caused data loss to the content of locked files.
In particular, when two files had the same content, and one was unlocked
and modified, with annex.thin that can corrupt the content of the
annex object, and so fsck on the other file should detect that.

getKeyStatus was relying on Database.Keys.getAssociatedFiles to tell
when a file is unlocked, but that can false positive because the
database can list old associated files.

Instead, separate out the case of unlocked object which has multiple
hardlinks when annex.thin is in use.
2019-03-18 15:59:43 -04:00

99 lines
3.2 KiB
Haskell

{- git-annex command
-
- Copyright 2011 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Command.Migrate where
import Command
import Backend
import Types.Backend (canUpgradeKey, fastMigrate)
import Types.KeySource
import Annex.Content
import qualified Command.ReKey
import qualified Command.Fsck
import qualified Annex
import Logs.MetaData
import Logs.Web
cmd :: Command
cmd = notDirect $ withGlobalOptions [annexedMatchingOptions] $
command "migrate" SectionUtility
"switch data to different backend"
paramPaths (withParams seek)
seek :: CmdParams -> CommandSeek
seek = withFilesInGit (commandAction . (whenAnnexed start)) <=< workTreeItems
start :: FilePath -> Key -> CommandStart
start file key = do
forced <- Annex.getState Annex.force
v <- Backend.getBackend file key
case v of
Nothing -> stop
Just oldbackend -> do
exists <- inAnnex key
newbackend <- maybe defaultBackend return
=<< chooseBackend file
if (newbackend /= oldbackend || upgradableKey oldbackend key || forced) && exists
then do
showStart "migrate" file
next $ perform file key oldbackend newbackend
else stop
{- Checks if a key is upgradable to a newer representation.
-
- Reasons for migration:
- - Ideally, all keys have file size metadata. Old keys may not.
- - Something has changed in the backend, such as a bug fix.
-}
upgradableKey :: Backend -> Key -> Bool
upgradableKey backend key = isNothing (keySize key) || backendupgradable
where
backendupgradable = maybe False (\a -> a key) (canUpgradeKey backend)
{- Store the old backend's key in the new backend
- The old backend's key is not dropped from it, because there may
- be other files still pointing at that key.
-
- To ensure that the data we have for the old key is valid, it's
- fscked here. First we generate the new key. This ensures that the
- data cannot get corrupted after the fsck but before the new key is
- generated.
-}
perform :: FilePath -> Key -> Backend -> Backend -> CommandPerform
perform file oldkey oldbackend newbackend = go =<< genkey (fastMigrate oldbackend)
where
go Nothing = stop
go (Just (newkey, knowngoodcontent))
| knowngoodcontent = finish newkey
| otherwise = stopUnless checkcontent $ finish newkey
checkcontent = Command.Fsck.checkBackend oldbackend oldkey Command.Fsck.KeyPresent afile
finish newkey = ifM (Command.ReKey.linkKey file oldkey newkey)
( do
_ <- copyMetaData oldkey newkey
-- If the old key had some associated urls, record them for
-- the new key as well.
urls <- getUrls oldkey
forM_ urls $ \url ->
setUrlPresent newkey url
next $ Command.ReKey.cleanup file oldkey newkey
, giveup "failed creating link from old to new key"
)
genkey Nothing = do
content <- calcRepo $ gitAnnexLocation oldkey
let source = KeySource
{ keyFilename = file
, contentLocation = content
, inodeCache = Nothing
}
v <- genKey source (Just newbackend)
return $ case v of
Just (newkey, _) -> Just (newkey, False)
_ -> Nothing
genkey (Just fm) = fm oldkey newbackend afile >>= \case
Just newkey -> return (Just (newkey, True))
Nothing -> genkey Nothing
afile = AssociatedFile (Just file)