metadata: Put journal in $XDG_RUNTIME_DIR for shared NFS homedir case

This essentially moves is_on_nfs() from metatree.c in metabuilder.c
as the more appropriate place for shared functions. It's used in
meta_builder_get_journal_filename() to determine whether to use original
metadata directory or temporary $XDG_RUNTIME_DIR location to work around
certain NFS issues.

The idea behind this change is to have separate journals for every client
that is accessing shared homedir. Then the only possible point of conflict
is on rotation which is backed up by atomic file rename. Without this,
there were multiple metadata daemons writing to the same journal file,
overwriting changes to each other and being racy in flush and rotation.

There will always be a conflict between clients, overwriting tree file
data by flushing their journals.

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

1 files changed, 131 insertions, 4 deletions

diff --git a/metadata/metabuilder.c b/metadata/metabuilder.c
index c7e69fac..af9e99da 100644
--- a/metadata/metabuilder.c
+++ b/metadata/metabuilder.c
@@ -1,3 +1,4 @@
+#include "config.h"
 #include "metabuilder.h"
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -8,6 +9,44 @@
 #include <sys/mman.h>
 #include <glib/gstdio.h>
 
+#if HAVE_SYS_STATFS_H
+#include <sys/statfs.h>
+#endif
+#if HAVE_SYS_STATVFS_H
+#include <sys/statvfs.h>
+#endif
+#if HAVE_SYS_VFS_H
+#include <sys/vfs.h>
+#elif HAVE_SYS_MOUNT_H
+#if HAVE_SYS_PARAM_H
+#include <sys/param.h>
+#endif
+#include <sys/mount.h>
+#endif
+
+#if defined(HAVE_STATFS) && defined(HAVE_STATVFS)
+/* Some systems have both statfs and statvfs, pick the
+   most "native" for these */
+# if !defined(HAVE_STRUCT_STATFS_F_BAVAIL)
+   /* on solaris and irix, statfs doesn't even have the
+      f_bavail field */
+#  define USE_STATVFS
+# else
+  /* at least on linux, statfs is the actual syscall */
+#  define USE_STATFS
+# endif
+
+#elif defined(HAVE_STATFS)
+
+# define USE_STATFS
+
+#elif defined(HAVE_STATVFS)
+
+# define USE_STATVFS
+
+#endif
+
+
 #define MAJOR_VERSION 1
 #define MINOR_VERSION 0
 #define MAJOR_JOURNAL_VERSION 1
@@ -825,12 +864,89 @@ write_all_data_and_close (int fd, char *data, gsize len)
   return res;
 }
 
+gboolean
+meta_builder_is_on_nfs (const char *filename)
+{
+#ifdef USE_STATFS
+  struct statfs statfs_buffer;
+  int statfs_result;
+#elif defined(USE_STATVFS) && defined(HAVE_STRUCT_STATVFS_F_BASETYPE)
+  struct statvfs statfs_buffer;
+  int statfs_result;
+#endif
+  char *dirname;
+  gboolean res;
+
+  dirname = g_path_get_dirname (filename);
+
+  res = FALSE;
+
+#ifdef USE_STATFS
+
+# if STATFS_ARGS == 2
+  statfs_result = statfs (dirname, &statfs_buffer);
+# elif STATFS_ARGS == 4
+  statfs_result = statfs (dirname, &statfs_buffer,
+                          sizeof (statfs_buffer), 0);
+# endif
+  if (statfs_result == 0)
+#ifdef __OpenBSD__
+    res = strcmp(statfs_buffer.f_fstypename, MOUNT_NFS) == 0;
+#else
+    res = statfs_buffer.f_type == 0x6969;
+#endif
+
+#elif defined(USE_STATVFS) && defined(HAVE_STRUCT_STATVFS_F_BASETYPE)
+  statfs_result = statvfs (dirname, &statfs_buffer);
+
+  if (statfs_result == 0)
+    res = strcmp (statfs_buffer.f_basetype, "nfs") == 0;
+#endif
+
+  g_free (dirname);
+
+  return res;
+}
+
 static char *
-get_journal_filename (const char *filename, guint32 random_tag)
+get_runtime_journal_dir (const char *tree_filename)
+{
+  const char *rd;
+  char *dbname;
+  char *real_path;
+  char *ret;
+
+  rd = g_get_user_runtime_dir ();
+  if (! rd || *rd == '\0')
+    return NULL;
+
+  real_path = g_build_filename (rd, "gvfs-metadata", NULL);
+  if (! g_file_test (real_path, G_FILE_TEST_EXISTS))
+    {
+      if (g_mkdir_with_parents (real_path, 0700) != 0)
+        {
+          g_free (real_path);
+          return NULL;
+        }
+    }
+
+  dbname = g_path_get_basename (tree_filename);
+  ret = g_build_filename (real_path, dbname, NULL);
+
+  g_free (dbname);
+  g_free (real_path);
+
+  return ret;
+}
+
+char *
+meta_builder_get_journal_filename (const char *tree_filename, guint32 random_tag)
 {
   const char *hexdigits = "0123456789abcdef";
   char tag[9];
   int i;
+  char *ret;
+  char *real_filename = NULL;
 
   for (i = 7; i >= 0; i--)
     {
@@ -840,7 +956,18 @@ get_journal_filename (const char *filename, guint32 random_tag)
 
   tag[8] = 0;
 
-  return g_strconcat (filename, "-", tag, ".log", NULL);
+  if (meta_builder_is_on_nfs (tree_filename))
+    {
+      /* Put the journal in $XDG_RUNTIME_DIR to avoid file usage from concurrent clients */
+      real_filename = get_runtime_journal_dir (tree_filename);
+    }
+
+  if (! real_filename)
+    return g_strconcat (tree_filename, "-", tag, ".log", NULL);
+
+  ret = g_strconcat (real_filename, "-", tag, ".log", NULL);
+  g_free (real_filename);
+  return ret;
 }
 
 gboolean
@@ -852,7 +979,7 @@ meta_builder_create_new_journal (const char *filename, guint32 random_tag)
   gsize pos;
   gboolean res;
 
-  journal_name = get_journal_filename (filename, random_tag);
+  journal_name = meta_builder_get_journal_filename (filename, random_tag);
 
   out = g_string_new (NULL);
 
@@ -1055,7 +1182,7 @@ meta_builder_write (MetaBuilder *builder,
 	  munmap (data, RANDOM_TAG_OFFSET + 4);
 	  close (fd2);
 
-	  old_log = get_journal_filename (filename, old_tag);
+	  old_log = meta_builder_get_journal_filename (filename, old_tag);
 	  g_unlink (old_log);
 	  g_free (old_log);
 	}