Bug#239111: Freeze when installing GRUB on XFS boot partition

[Ben Hutchings]

The grub shell already does sync() - many times - so I think we can just
change xfs_freeze.diff to:

--- grub-0.97.orig/util/grub-install.in	2004-07-24 19:57:31.000000000 +0100
+++ grub-0.97/util/grub-install.in	2009-01-04 04:57:47.000000000 +0000
@@ -418,6 +418,12 @@
 # Make a default file.
 ${grub_set_default} --root-directory=${rootdir} default
 
+# XFS is special; we must run xfs_freeze to flush files as well as sync
+# (which grub itself does).
+if [ "$(stat -f --printf=%T ${grubdir})" = "xfs" ]; then
+    xfs_freeze -f ${grubdir} && xfs_freeze -u ${grubdir}
+fi
+
 # Make sure that GRUB reads the same images as the host OS.
 test -n "$mkimg" && img_file=`$mkimg`
 test -n "$mklog" && log_file=`$mklog`
--- END ---

It is probably better to use FIBMAP, but it's kind of hard to map a
device name to a mount point.  The following is an attempt to do that.
It does not use the result of FIBMAP but only uses it to force block
allocation.

However, somehow this triggers "Error 28: Selected item cannot fit into
memory".  So it should certainly not be applied, but it may be useful to
anyone who wants to investigate further. 

--- grub-0.97.orig/stage2/disk_io.c	2004-05-23 17:35:24.000000000 +0100
+++ grub-0.97/stage2/disk_io.c	2009-01-04 06:36:26.000000000 +0000
@@ -29,6 +29,17 @@
 
 #ifdef GRUB_UTIL
 # include <device.h>
+# ifdef __linux__
+#   include <errno.h>
+#   include <stdio.h>
+#   include <stdlib.h>
+#   include <sys/types.h>
+#   include <unistd.h>
+#   include <fcntl.h>
+#   include <sys/ioctl.h>
+#   include <sys/stat.h>
+#   include <linux/fs.h>
+# endif
 #endif
 
 /* instrumentation variables */
@@ -1530,6 +1541,124 @@
 #endif /* STAGE1_5 */
 
 
+#if defined(GRUB_UTIL) && defined(__linux__)
+
+static int
+find_mount_point (dev_t block_dev, char **p_mount_point)
+{
+  static char line[256];
+
+  struct stat stats;
+  FILE *mounts;
+  char *begin, *end, *mount_point;
+  int result = -1;
+
+  mounts = fopen ("/proc/mounts", "r");
+  if (!mounts)
+    return -1;
+
+  errno = 0;
+  mount_point = NULL;
+  while (fgets (line, sizeof(line), mounts))
+    {
+      if (line[0] != '/')
+	continue;
+      end = strstr (line, " ");
+      if (!end)
+	goto out_close;
+      *end = 0;
+      if (stat (line, &stats))
+	goto out_close;
+      if (S_ISBLK (stats.st_mode) && stats.st_rdev == block_dev)
+	{
+	  begin = end + 1;
+	  end = strstr (begin, " ");
+	  if (!end)
+	    goto out_close;
+	  *end = 0;
+	  mount_point = malloc (end + 1 - begin);
+	  if (!mount_point)
+	    goto out_close;
+	  strcpy (mount_point, begin);
+	  break;
+	}
+    }
+  if (errno == 0)
+    {
+      free (*p_mount_point);
+      *p_mount_point = mount_point;
+      result = 0;
+    }
+
+ out_close:
+  fclose(mounts);
+  return result;
+}
+
+/*
+ * If filename is on a mounted filesystem, get its block list, forcing
+ * block allocation on a filesystem with deferred allocation.
+ */
+static int
+map_file (char *filename)
+{
+  static char *mount_point;
+  static dev_t cached_block_dev;
+  static char full_filename[PATH_MAX];
+
+  dev_t block_dev;
+  int block_fd = buf_geom.flags, fd;
+  struct stat stats;
+  unsigned long block_num;
+  int result = -1;
+
+  if (fstat (block_fd, &stats) || !S_ISBLK (stats.st_mode))
+    return -1;
+
+  block_dev = stats.st_rdev;
+  if ((current_partition & 0x00FF00) == 0x00FF00)
+    block_dev += ((current_partition >> 16) & 0xFF) + 1;
+  if (block_dev != cached_block_dev &&
+      find_mount_point(block_dev, &mount_point))
+    return -1;
+  cached_block_dev = block_dev;
+
+  if (!mount_point)
+    return 0;
+
+  if (snprintf (full_filename, sizeof(full_filename),
+		"%s%s", mount_point, filename) >=
+      sizeof(full_filename))
+    return -1;
+  fd = open (full_filename, O_RDONLY);
+  if (fd < 0)
+    return -1;
+
+  if (fstat (fd, &stats))
+    goto out_close;
+  for (block_num = 0;
+       block_num < (stats.st_size + stats.st_blksize - 1) / stats.st_blksize;
+       block_num++)
+    if (ioctl (fd, FIBMAP, &block_num) < 0)
+      goto out_close;
+  result = 0;
+
+ out_close:
+  close (fd);
+  return result;
+}
+
+#else /* !(GRUB_UTIL && __linux__) */
+
+static int
+map_file (char *filename)
+{
+  return 0;
+}
+
+#endif /* GRUB_UTIL && __linux__ */
+
+
 /*
  *  This is the generic file open function.
  */
@@ -1622,6 +1751,11 @@
       errnum = ERR_BAD_FILENAME;
 #endif /* NO_BLOCK_FILES */
     }
+  else /* normal filename */
+    {
+      if (map_file (filename))
+	errnum = ERR_DEV_VALUES;
+    }
 
   if (!errnum && fsys_type == NUM_FSYS)
     errnum = ERR_FSYS_MOUNT;
--- END ---

Ben.

-- 
Ben Hutchings
[W]e found...that it wasn't as easy to get programs right as we had thought.
... I realized that a large part of my life from then on was going to be spent
in finding mistakes in my own programs. - Maurice Wilkes, 1949
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