metadata: Create new journal if it doesn't exist

With concurrent access of multiple daemons there may be a moment when
tree file exists but not the journal file. The daemon can't write
anything without journal and is doomed until next rotation. Missing
journal file can also happen on system crash etc.

This patch tries to create new journal file only when it doesn't exist,
other errors still lead to inability to store anything.

This will also allow us to have journal file somewhere else, e.g. on
a non-persistent storage.

https://bugzilla.gnome.org/show_bug.cgi?id=637095

3 files changed, 18 insertions, 6 deletions

diff --git a/metadata/metabuilder.c b/metadata/metabuilder.c
index 58bb57bd..c7e69fac 100644
--- a/metadata/metabuilder.c
+++ b/metadata/metabuilder.c
@@ -843,8 +843,8 @@ get_journal_filename (const char *filename, guint32 random_tag)
   return g_strconcat (filename, "-", tag, ".log", NULL);
 }
 
-static gboolean
-create_new_journal (const char *filename, guint32 random_tag)
+gboolean
+meta_builder_create_new_journal (const char *filename, guint32 random_tag)
 {
   char *journal_name;
   guint32 size_offset;
@@ -1016,7 +1016,7 @@ meta_builder_write (MetaBuilder *builder,
   if (!write_all_data_and_close (fd, out->str, out->len))
     goto out;
 
-  if (!create_new_journal (filename, random_tag))
+  if (!meta_builder_create_new_journal (filename, random_tag))
     goto out;
 
   /* Open old file so we can set it rotated */
diff --git a/metadata/metabuilder.h b/metadata/metabuilder.h
index 364c0d84..ad3876ff 100644
--- a/metadata/metabuilder.h
+++ b/metadata/metabuilder.h
@@ -68,6 +68,8 @@ void         meta_builder_copy      (MetaBuilder *builder,
 				     guint64      mtime);
 gboolean     meta_builder_write     (MetaBuilder *builder,
 				     const char  *filename);
+gboolean     meta_builder_create_new_journal (const char *filename,
+				     guint32      random_tag);
 MetaFile *   metafile_new           (const char  *name,
 				     MetaFile    *parent);
 void         metafile_free          (MetaFile    *file);
diff --git a/metadata/metatree.c b/metadata/metatree.c
index 20b78627..8e2ab46c 100644
--- a/metadata/metatree.c
+++ b/metadata/metatree.c
@@ -1146,20 +1146,30 @@ meta_journal_open (MetaTree *tree, const char *filename, gboolean for_write, gui
   char *data;
   char *journal_filename;
   int open_flags, mmap_prot;
+  gboolean retried;
 
   g_assert (sizeof (MetaJournalHeader) == 20);
-
-  journal_filename = get_journal_filename (filename, tag);
+  retried = FALSE;
 
   if (for_write)
     open_flags = O_RDWR;
   else
     open_flags = O_RDONLY;
 
+ retry:
+  journal_filename = get_journal_filename (filename, tag);
   fd = safe_open (tree, journal_filename, open_flags);
   g_free (journal_filename);
   if (fd == -1)
-    return NULL;
+    {
+      if (errno == ENOENT && tree->for_write && !retried)
+        {
+          retried = TRUE;
+          if (meta_builder_create_new_journal (filename, tag))
+            goto retry;
+        }
+      return NULL;
+    }
 
   if (fstat (fd, &statbuf) != 0 ||
       statbuf.st_size < sizeof (MetaJournalHeader))