repo: Allocate a tmpdir for each OstreeFetcher to isolate concurrent downloads

This way two pulls will not use the same tmpdir and accidentally
overwrite each other. However, consecutive OstreeFetchers will reuse
the tmpdirs, so that we can properly resume downloading large objects.

https://bugzilla.gnome.org/show_bug.cgi?id=757611

src/libostree/ostree-fetcher.c

@@ -30,6 +30,7 @@
 #include "ostree-tls-cert-interaction.h"
 #endif
 #include "ostree.h"
+#include "ostree-repo-private.h"
 #include "otutil.h"
 
 typedef enum {
@@ -63,6 +64,9 @@ struct OstreeFetcher
   GObject parent_instance;
 
   int tmpdir_dfd;
+  char *tmpdir_name;
+  GLnxLockFile tmpdir_lock;
+  int base_tmpdir_dfd;
 
   GTlsCertificate *client_cert;
 
@@ -114,6 +118,17 @@ _ostree_fetcher_finalize (GObject *object)
 
   self = OSTREE_FETCHER (object);
 
+  if (self->tmpdir_dfd != -1)
+    close (self->tmpdir_dfd);
+
+  /* Note: We don't remove the tmpdir here, because that would cause
+     us to not reuse it on resume. This happens because we use two
+     fetchers for each pull, so finalizing the first one would remove
+     all the files to be resumed from the previous second one */
+
+  g_free (self->tmpdir_name);
+  glnx_release_lock_file (&self->tmpdir_lock);
+
   g_clear_object (&self->session);
   g_clear_object (&self->client_cert);
 
@@ -140,6 +155,7 @@ _ostree_fetcher_init (OstreeFetcher *self)
 {
   gint max_conns;
   const char *http_proxy;
+  GLnxLockFile empty_lockfile = GLNX_LOCK_FILE_INIT;
 
   g_queue_init (&self->pending_queue);
   self->session = soup_session_async_new_with_options (SOUP_SESSION_USER_AGENT, "ostree ",
@@ -174,18 +190,33 @@ _ostree_fetcher_init (OstreeFetcher *self)
   self->output_stream_set = g_hash_table_new_full (NULL, NULL, NULL, (GDestroyNotify)g_object_unref);
 
   self->outstanding = g_hash_table_new_full (NULL, NULL, NULL, NULL);
+
+  self->tmpdir_dfd = -1;
+  self->tmpdir_lock = empty_lockfile;
+
 }
 
 OstreeFetcher *
 _ostree_fetcher_new (int                      tmpdir_dfd,
-                    OstreeFetcherConfigFlags  flags)
+                     OstreeFetcherConfigFlags flags,
+                     GCancellable            *cancellable,
+                     GError                 **error)
 {
   OstreeFetcher *self = (OstreeFetcher*)g_object_new (OSTREE_TYPE_FETCHER, NULL);
 
-  self->tmpdir_dfd = tmpdir_dfd;
+  if (!_ostree_repo_allocate_tmpdir (tmpdir_dfd,
+                                     "fetcher-",
+                                     &self->tmpdir_name,
+                                     &self->tmpdir_dfd,
+                                     &self->tmpdir_lock,
+                                     NULL,
+                                     cancellable, error))
+    return NULL;
+
+  self->base_tmpdir_dfd = tmpdir_dfd;
   if ((flags & OSTREE_FETCHER_FLAGS_TLS_PERMISSIVE) > 0)
     g_object_set ((GObject*)self->session, "ssl-strict", FALSE, NULL);
- 
+
   return self;
 }