Remove setting of the immutable bit

Using the immutable bit is problematic, especially in conjunction with
store optimisation.  For instance, if the garbage collector deletes a
file, it has to clear its immutable bit, but if the file has
additional hard links, we can't set the bit afterwards because we
don't know the remaining paths.

So now that we support having the entire Nix store as a read-only
mount, we may as well drop the immutable bit.  Unfortunately, we have
to keep the code to clear the immutable bit for backwards
compatibility.

1 files changed, 2 insertions, 11 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 0b7790a5bb87..4051adacca0b 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1355,11 +1355,6 @@ void DerivationGoal::buildDone()
         /* Delete the chroot (if we were using one). */
         autoDelChroot.reset(); /* this runs the destructor */
 
-        /* Deleting the chroot will have caused the immutable bits on
-           hard-linked inputs to be cleared.  So set them again. */
-        foreach (PathSet::iterator, i, regularInputPaths)
-            makeImmutable(*i);
-
         /* Delete redirected outputs (when doing hash rewriting). */
         foreach (PathSet::iterator, i, redirectedOutputs)
             deletePath(*i);
@@ -1766,11 +1761,8 @@ void DerivationGoal::startBuilder()
                     /* Hard-linking fails if we exceed the maximum
                        link count on a file (e.g. 32000 of ext3),
                        which is quite possible after a `nix-store
-                       --optimise'.  It can also fail if another
-                       process called makeImmutable() on *i after we
-                       did makeMutable().  In those cases, make a copy
-                       instead. */
-                    if (errno != EMLINK && errno != EPERM)
+                       --optimise'. */
+                    if (errno != EMLINK)
                         throw SysError(format("linking `%1%' to `%2%'") % p % *i);
                     StringSink sink;
                     dumpPath(*i, sink);
@@ -1778,7 +1770,6 @@ void DerivationGoal::startBuilder()
                     restorePath(p, source);
                 }
 
-                makeImmutable(*i);
                 regularInputPaths.insert(*i);
             }
         }