[ostree] repo: Disable uncompressed object cache on non-writable repos

[Colin Walters <walters src gnome org>]

commit 884a9b27e91c728c5b25799e807129cd3fdf1ba4
Author: Colin Walters <walters verbum org>
Date:   Thu Oct 16 14:54:34 2014 -0400

    repo: Disable uncompressed object cache on non-writable repos
    
    While we did support disabling the uncompressed-objects-cache
    per-repository:
    
    1) We didn't actually respect that operation when doing
       CHECKOUT_MODE_USER on archive-z2 repositories
    2) It'd be better to automatically detect we can't write to the
       repo and disable the uncompressed cache then.

 src/libostree/ostree-repo-checkout.c |    3 ++-
 src/libostree/ostree-repo-private.h  |    1 +
 src/libostree/ostree-repo.c          |   24 +++++++++++++-----------
 3 files changed, 16 insertions(+), 12 deletions(-)
---
diff --git a/src/libostree/ostree-repo-checkout.c b/src/libostree/ostree-repo-checkout.c
index 417e11f..2963996 100644
--- a/src/libostree/ostree-repo-checkout.c
+++ b/src/libostree/ostree-repo-checkout.c
@@ -392,7 +392,8 @@ checkout_one_file_at (OstreeRepo                        *repo,
           gboolean is_bare = (current_repo->mode == OSTREE_REPO_MODE_BARE
                               && mode == OSTREE_REPO_CHECKOUT_MODE_NONE);
           gboolean is_archive_z2_with_cache = (current_repo->mode == OSTREE_REPO_MODE_ARCHIVE_Z2
-                                               && mode == OSTREE_REPO_CHECKOUT_MODE_USER);
+                                               && mode == OSTREE_REPO_CHECKOUT_MODE_USER
+                                               && current_repo->enable_uncompressed_cache);
 
           /* But only under these conditions */
           if (is_bare || is_archive_z2_with_cache)
diff --git a/src/libostree/ostree-repo-private.h b/src/libostree/ostree-repo-private.h
index 34f6cde..ad512f9 100644
--- a/src/libostree/ostree-repo-private.h
+++ b/src/libostree/ostree-repo-private.h
@@ -58,6 +58,7 @@ struct OstreeRepo {
   GPtrArray *cached_content_indexes;
 
   gboolean inited;
+  gboolean writable;
   gboolean in_transaction;
   gboolean disable_fsync;
   GHashTable *loose_object_devino_hash;
diff --git a/src/libostree/ostree-repo.c b/src/libostree/ostree-repo.c
index c706640..bddfbfb 100644
--- a/src/libostree/ostree-repo.c
+++ b/src/libostree/ostree-repo.c
@@ -752,14 +752,14 @@ ostree_repo_open (OstreeRepo    *self,
   if (self->inited)
     return TRUE;
 
-  if (!g_file_test (gs_file_get_path_cached (self->objects_dir), G_FILE_TEST_IS_DIR))
+  if (!gs_file_open_dir_fd (self->objects_dir, &self->objects_dir_fd, cancellable, error))
     {
-      g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND,
-                   "Couldn't find objects directory '%s'",
-                   gs_file_get_path_cached (self->objects_dir));
+      g_prefix_error (error, "Reading objects/ directory: ");
       goto out;
     }
 
+  self->writable = faccessat (AT_FDCWD, gs_file_get_path_cached (self->objects_dir), W_OK, 0) == 0;
+
   self->config = g_key_file_new ();
   if (!g_key_file_load_from_file (self->config, gs_file_get_path_cached (self->config_file), 0, error))
     {
@@ -812,9 +812,14 @@ ostree_repo_open (OstreeRepo    *self,
         }
     }
 
-  if (!ot_keyfile_get_boolean_with_default (self->config, "core", "enable-uncompressed-cache",
-                                            TRUE, &self->enable_uncompressed_cache, error))
-    goto out;
+  if (self->writable)
+    {
+      if (!ot_keyfile_get_boolean_with_default (self->config, "core", "enable-uncompressed-cache",
+                                                TRUE, &self->enable_uncompressed_cache, error))
+        goto out;
+    }
+  else
+    self->enable_uncompressed_cache = FALSE;
 
   {
     gboolean do_fsync;
@@ -837,13 +842,10 @@ ostree_repo_open (OstreeRepo    *self,
       }
   }
 
-  if (!gs_file_open_dir_fd (self->objects_dir, &self->objects_dir_fd, cancellable, error))
-    goto out;
-
   if (!gs_file_open_dir_fd (self->tmp_dir, &self->tmp_dir_fd, cancellable, error))
     goto out;
 
-  if (self->mode == OSTREE_REPO_MODE_ARCHIVE_Z2)
+  if (self->mode == OSTREE_REPO_MODE_ARCHIVE_Z2 && self->enable_uncompressed_cache)
     {
       if (!gs_file_ensure_directory (self->uncompressed_objects_dir, TRUE, cancellable, error))
         goto out;