* Sync with the trunk.

release.nix

@@ -1,5 +1,5 @@
 { nixpkgs ? <nixpkgs>, nixos ? <nixos>
-, nix ? { outPath = ../nix-export; rev = 1234; }
+, nix ? { outPath = ./.; rev = 1234; }
 , officialRelease ? false
 }:
 
@@ -98,7 +98,7 @@ let
           ];
 
         configureFlags = ''
-          --disable-init-state --disable-shared
+          --disable-init-state
           --with-bzip2=${bzip2} --with-sqlite=${sqlite}
           --with-dbi=${perlPackages.DBI}/lib/perl5/site_perl
           --with-dbd-sqlite=${perlPackages.DBDSQLite}/lib/perl5/site_perl

scripts/build-remote.pl.in

@@ -1,6 +1,6 @@
 #! @perl@ -w @perlFlags@
 
-use Fcntl ':flock';
+use Fcntl qw(:DEFAULT :flock);
 use English '-no_match_vars';
 use IO::Handle;
 use Nix::Config;
@@ -56,7 +56,7 @@ sub openSlotLock {
     my ($machine, $slot) = @_;
     my $slotLockFn = "$currentLoad/" . (join '+', @{$machine->{systemTypes}}) . "-" . $machine->{hostName} . "-$slot";
     my $slotLock = new IO::Handle;
-    open $slotLock, ">>$slotLockFn" or die;
+    sysopen $slotLock, "$slotLockFn", O_RDWR|O_CREAT, 0600 or die;
     return $slotLock;
 }
 
@@ -104,7 +104,7 @@ REQ: while (1) {
     # Acquire the exclusive lock on $currentLoad/main-lock.
     mkdir $currentLoad, 0777 or die unless -d $currentLoad;
     my $mainLock = "$currentLoad/main-lock";
-    open MAINLOCK, ">>$mainLock" or die;
+    sysopen MAINLOCK, "$mainLock", O_RDWR|O_CREAT, 0600 or die;
     flock(MAINLOCK, LOCK_EX) or die;
     
     
@@ -225,8 +225,17 @@ sub removeRoots {
 }
 
 
-# Copy the derivation and its dependencies to the build machine.
+# Copy the derivation and its dependencies to the build machine.  This
+# is guarded by an exclusive lock per machine to prevent multiple
+# build-remote instances from copying to a machine simultaneously.
+# That's undesirable because we may end up with N instances uploading
+# the same missing path simultaneously, causing the effective network
+# bandwidth and target disk speed to be divided by N.
+my $uploadLock = "$currentLoad/$hostName.upload-lock";
+sysopen MAINLOCK, "$uploadLock", O_RDWR|O_CREAT, 0600 or die;
+flock(MAINLOCK, LOCK_EX) or die;
 Nix::CopyClosure::copyTo($hostName, [ @sshOpts ], [ $drvPath, @inputs ], "", "", 0, 0, $maybeSign ne "");
+close MAINLOCK;
 
 
 # Perform the build.

src/libstore/build.cc

@@ -1300,6 +1300,13 @@ void DerivationGoal::buildDone()
            being valid. */
         computeClosure();
 
+        /* It is now safe to delete the lock files, since all future
+           lockers will see that the output paths are valid; they will
+           not create new lock files with the same names as the old
+           (unlinked) lock files. */
+        outputLocks.setDeletion(true);
+        outputLocks.unlock();
+
     } catch (BuildError & e) {
         printMsg(lvlError, e.msg());
         outputLocks.unlock();
@@ -1987,13 +1994,6 @@ void DerivationGoal::computeClosure()
         infos.push_back(info);
     }
     worker.store.registerValidPaths(infos);
-
-    /* It is now safe to delete the lock files, since all future
-       lockers will see that the output paths are valid; they will not
-       create new lock files with the same names as the old (unlinked)
-       lock files. */
-    outputLocks.setDeletion(true);
-    outputLocks.unlock();
 }
 
 

src/libstore/gc.cc

@@ -617,24 +617,48 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
         
     } else {
         
-        printMsg(lvlError, format("reading the Nix store..."));
-        Paths entries = readDirectory(nixStore);
-
-        /* Randomise the order in which we delete entries to make the
-           collector less biased towards deleting paths that come
-           alphabetically first (e.g. /nix/store/000...).  This
-           matters when using --max-freed etc. */
-        vector<Path> entries_(entries.begin(), entries.end());
-        random_shuffle(entries_.begin(), entries_.end());
-
         if (shouldDelete(state.options.action))
             printMsg(lvlError, format("deleting garbage..."));
         else
             printMsg(lvlError, format("determining live/dead paths..."));
     
         try {
+
+            AutoCloseDir dir = opendir(nixStore.c_str());
+            if (!dir) throw SysError(format("opening directory `%1%'") % nixStore);
+
+            /* Read the store and immediately delete all paths that
+               aren't valid.  When using --max-freed etc., deleting
+               invalid paths is preferred over deleting unreachable
+               paths, since unreachable paths could become reachable
+               again.  We don't use readDirectory() here so that GCing
+               can start faster. */
+            Paths entries;
+            struct dirent * dirent;
+            while (errno = 0, dirent = readdir(dir)) {
+                checkInterrupt();
+                string name = dirent->d_name;
+                if (name == "." || name == "..") continue;
+                Path path = nixStore + "/" + name;
+                if (isValidPath(path))
+                    entries.push_back(path);
+                else
+                    tryToDelete(state, path);
+            }
+
+	    dir.close();
+
+            /* Now delete the unreachable valid paths.  Randomise the
+               order in which we delete entries to make the collector
+               less biased towards deleting paths that come
+               alphabetically first (e.g. /nix/store/000...).  This
+               matters when using --max-freed etc. */
+            vector<Path> entries_(entries.begin(), entries.end());
+            random_shuffle(entries_.begin(), entries_.end());
+
             foreach (vector<Path>::iterator, i, entries_)
-                tryToDelete(state, canonPath(nixStore + "/" + *i));
+                tryToDelete(state, *i);
+
         } catch (GCLimitReached & e) {
         }
     }

src/libstore/pathlocks.cc

@@ -16,7 +16,7 @@ int openLockFile(const Path & path, bool create)
 {
     AutoCloseFD fd;
 
-    fd = open(path.c_str(), O_RDWR | (create ? O_CREAT : 0), 0666);
+    fd = open(path.c_str(), O_RDWR | (create ? O_CREAT : 0), 0600);
     if (fd == -1 && (create || errno != ENOENT))
         throw SysError(format("opening lock file `%1%'") % path);
 

src/libutil/util.cc

@@ -701,7 +701,7 @@ AutoCloseDir::AutoCloseDir(DIR * dir)
 
 AutoCloseDir::~AutoCloseDir()
 {
-    if (dir) closedir(dir);
+    close();
 }
 
 
@@ -717,6 +717,14 @@ AutoCloseDir::operator DIR *()
 }
 
 
+void AutoCloseDir::close()
+{
+    if (dir) {
+	closedir(dir);
+	dir = 0;
+    }
+}
+
 
 //////////////////////////////////////////////////////////////////////
 

src/libutil/util.hh

@@ -223,6 +223,7 @@ public:
     ~AutoCloseDir();
     void operator =(DIR * dir);
     operator DIR *();
+    void close();
 };
 
 

tests/lang/eval-okay-search-path.nix~

@@ -1 +0,0 @@
-(import <a.nix>)

tests/lang/eval-okay-search-path.out

@@ -1 +0,0 @@
-"abcc"