Revert "Fix hard linking issue causing overlay fs copy-ups"

This reverts commit 9ef0a9e8aa.

Master now has a better solution.

src/libstore/build/local-derivation-goal.cc

@@ -388,9 +388,8 @@ void LocalDerivationGoal::cleanupPostOutputsRegisteredModeNonCheck()
 
 
 #if __linux__
-static void linkOrCopy(LocalFSStore & store, const StorePath & from_, const Path & to)
+static void linkOrCopy(const Path & from, const Path & to)
 {
-    auto from = store.toRealPathForHardLink(from_);
     if (link(from.c_str(), to.c_str()) == -1) {
         /* Hard-linking fails if we exceed the maximum link count on a
            file (e.g. 32000 of ext3), which is quite possible after a
@@ -715,7 +714,7 @@ void LocalDerivationGoal::startBuilder()
             if (S_ISDIR(lstat(r).st_mode))
                 dirsInChroot.insert_or_assign(p, r);
             else
-                linkOrCopy(getLocalStore(), i, chrootRootDir + p);
+                linkOrCopy(r, chrootRootDir + p);
         }
 
         /* If we're repairing, checking or rebuilding part of a
@@ -1600,7 +1599,7 @@ void LocalDerivationGoal::addDependency(const StorePath & path)
                     throw Error("could not add path '%s' to sandbox", worker.store.printStorePath(path));
 
             } else
-                linkOrCopy(getLocalStore(), path, target);
+                linkOrCopy(source, target);
 
         #else
             throw Error("don't know how to make path '%s' (produced by a recursive Nix call) appear in the sandbox",

src/libstore/local-fs-store.hh

@@ -73,16 +73,6 @@ public:
         return getRealStoreDir() + "/" + std::string(storePath, storeDir.size() + 1);
     }
 
-    /**
-     * If the real path is hardlinked with something else, we might
-     * prefer to refer to the other path instead. This is the case with
-     * overlayfs, for example.
-     */
-    virtual Path toRealPathForHardLink(const StorePath & storePath)
-    {
-        return Store::toRealPath(storePath);
-    }
-
     std::optional<std::string> getBuildLogExact(const StorePath & path) override;
 
 };

src/libstore/local-overlay-store.cc

@@ -268,14 +268,6 @@ std::pair<bool, StorePathSet> LocalOverlayStore::verifyAllValidPaths(RepairFlag
 }
 
 
-Path LocalOverlayStore::toRealPathForHardLink(const StorePath & path)
-{
-    return lowerStore->isValidPath(path)
-        ? lowerStore->Store::toRealPath(path)
-        : Store::toRealPath(path);
-}
-
-
 void LocalOverlayStore::remountIfNecessary()
 {
     if (!_remountRequired) return;

src/libstore/local-overlay-store.hh

@@ -186,12 +186,6 @@ private:
      */
     std::pair<bool, StorePathSet> verifyAllValidPaths(RepairFlag repair) override;
 
-    /**
-     * For lower-store paths, we used the lower store location. This avoids the
-     * wasteful "copying up" that would otherwise happen.
-     */
-    Path toRealPathForHardLink(const StorePath & storePath) override;
-
     /**
      * Deletion only effects the upper layer, so we ignore lower-layer referrers.
      */