Re: [PATCH stable-2.8 1/2] Add hs function to easily change file ownership

[Michele Tartara]

On Sat, Jul 13, 2013 at 11:40 AM, Michele Tartara <mtart...@google.com>wrote:

>
> Il giorno 12/lug/2013 20:44, "Iustin Pop" <iu...@k1024.org> ha scritto:
>
> >
> > On Fri, Jul 12, 2013 at 06:16:20PM +0200, Michele Tartara wrote:
> > > The haskell library functions only allow to change file ownership using
> > > uid/gid. A function for doing that with explicit names is added by this
> > > commit.
> > >
> > > Signed-off-by: Michele Tartara <mtart...@google.com>
> >
> > Hi Michele,
>
> Hi Iustin,
>
> >
> > > +-- | Set the owner and the group of a file (given as names, not
> numeric id).
> > > +setOwnerAndGroupFromNames :: FilePath -> String -> String -> IO ()
> > > +setOwnerAndGroupFromNames filename username groupname = do
> > > +  let nameUid = fmap userID (getUserEntryForName username)
> > > +      nameGid = fmap groupID (getGroupEntryForName groupname)
> > > +  uid <- nameUid
> > > +  gid <- nameGid
> > > +  setOwnerAndGroup filename uid gid
> >
> > Do you really need this to be generic? For ganeti-specific users, you
> > could/should use instead Runtime.hs/getEnts and the users/group maps it
> > returns, so that all name resolving is in a single place. Especially at
> > runtime, after the daemons have started, we should try to avoid user
> > lookups as depending on the nsswitch configuration this could have
> > arbitrary delays.
> >
> > iustin
>
> Of course, doing is for Ganeti users only is more than enough, but I
> didn't know we had uids and gods cached already.
>
> Thanks for pointing it out, I'll modify the function to use them.
>
> Thanks,
> Michele
>
Interdiff:
diff --git a/src/Ganeti/Utils.hs b/src/Ganeti/Utils.hs
index 92b5ed8..17b469a 100644
--- a/src/Ganeti/Utils.hs
+++ b/src/Ganeti/Utils.hs
@@ -62,16 +62,17 @@ module Ganeti.Utils
 import Data.Char (toUpper, isAlphaNum, isDigit, isSpace)
 import Data.Function (on)
 import Data.List
+import qualified Data.Map as M
 import Control.Monad (foldM)

 import Debug.Trace

 import Ganeti.BasicTypes
 import qualified Ganeti.Constants as C
+import Ganeti.Runtime
 import System.IO
 import System.Exit
 import System.Posix.Files
-import System.Posix.User
 import System.Time

 -- * Debug functions
@@ -436,10 +437,12 @@ recombineEithers lefts rights trail =
                                       show t

 -- | Set the owner and the group of a file (given as names, not numeric
id).
-setOwnerAndGroupFromNames :: FilePath -> String -> String -> IO ()
-setOwnerAndGroupFromNames filename username groupname = do
-  let nameUid = fmap userID (getUserEntryForName username)
-      nameGid = fmap groupID (getGroupEntryForName groupname)
-  uid <- nameUid
-  gid <- nameGid
+setOwnerAndGroupFromNames :: FilePath -> GanetiDaemon -> GanetiGroup -> IO
()
+setOwnerAndGroupFromNames filename daemon dGroup = do
+  runtimeEnts <- getEnts
+  ents <- exitIfBad "Can't find required user/groups" runtimeEnts
+   -- note: we use directly ! as lookup failues shouldn't happen, due
+  -- to the map construction
+  let uid = (fst ents) M.! daemon
+  let gid = (snd ents) M.! dGroup
   setOwnerAndGroup filename uid gid

Thanks,
Michele