Clear any immutable bits in the Nix store

Doing this once makes subsequent operations like garbage collecting
more efficient since we don't have to call makeMutable() first.

src/libstore/local-store.cc

@@ -5,7 +5,6 @@
 #include "pathlocks.hh"
 #include "worker-protocol.hh"
 #include "derivations.hh"
-#include "immutable.hh"
 
 #include <iostream>
 #include <algorithm>
@@ -25,6 +24,12 @@
 #include <sys/mount.h>
 #endif
 
+#if HAVE_LINUX_FS_H
+#include <linux/fs.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+#endif
+
 #include <sqlite3.h>
 
 
@@ -292,6 +297,7 @@ LocalStore::LocalStore(bool reserveSpace)
         curSchema = getSchema();
 
         if (curSchema < 6) upgradeStore6();
+        else if (curSchema < 7) upgradeStore7();
 
         writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
 
@@ -1787,6 +1793,59 @@ void LocalStore::upgradeStore6()
 }
 
 
+#if defined(FS_IOC_SETFLAGS) && defined(FS_IOC_GETFLAGS) && defined(FS_IMMUTABLE_FL)
+
+static void makeMutable(const Path & path)
+{
+    checkInterrupt();
+
+    struct stat st = lstat(path);
+
+    if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode)) return;
+
+    if (S_ISDIR(st.st_mode)) {
+        Strings names = readDirectory(path);
+        foreach (Strings::iterator, i, names)
+            makeMutable(path + "/" + *i);
+    }
+
+    /* The O_NOFOLLOW is important to prevent us from changing the
+       mutable bit on the target of a symlink (which would be a
+       security hole). */
+    AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW);
+    if (fd == -1) {
+        if (errno == ELOOP) return; // it's a symlink
+        throw SysError(format("opening file `%1%'") % path);
+    }
+
+    unsigned int flags = 0, old;
+
+    /* Silently ignore errors getting/setting the immutable flag so
+       that we work correctly on filesystems that don't support it. */
+    if (ioctl(fd, FS_IOC_GETFLAGS, &flags)) return;
+    old = flags;
+    flags &= ~FS_IMMUTABLE_FL;
+    if (old == flags) return;
+    if (ioctl(fd, FS_IOC_SETFLAGS, &flags)) return;
+}
+
+/* Upgrade from schema 6 (Nix 0.15) to schema 7 (Nix >= 1.3). */
+void LocalStore::upgradeStore7()
+{
+    if (getuid() != 0) return;
+    printMsg(lvlError, "removing immutable bits from the Nix store (this may take a while)...");
+    makeMutable(settings.nixStore);
+}
+
+#else
+
+void LocalStore::upgradeStore7()
+{
+}
+
+#endif
+
+
 void LocalStore::vacuumDB()
 {
     if (sqlite3_exec(db, "vacuum;", 0, 0, 0) != SQLITE_OK)