Index: fs/ext2.c
===================================================================
--- fs/ext2.c	(revisión: 1687)
+++ fs/ext2.c	(copia de trabajo)
@@ -50,6 +50,7 @@
 #include <grub/dl.h>
 #include <grub/types.h>
 #include <grub/fshelp.h>
+#include <grub/env.h>
 
 /* Log2 size of ext2 block in 512 blocks.  */
 #define LOG2_EXT2_BLOCK_SIZE(data)			\
@@ -71,8 +72,42 @@
          ? EXT2_GOOD_OLD_INODE_SIZE \
          : grub_le_to_cpu16 (data->sblock.inode_size))
 
-#define EXT3_FEATURE_COMPAT_HAS_JOURNAL	0x0004
+/* Superblock filesystem feature flags (RW compatible) */
+#define EXT2_FEATURE_COMPAT_DIR_PREALLOC	0x0001
+#define EXT2_FEATURE_COMPAT_IMAGIC_INODES	0x0002
+#define EXT3_FEATURE_COMPAT_HAS_JOURNAL		0x0004
+#define EXT2_FEATURE_COMPAT_EXT_ATTR		0x0008
+#define EXT2_FEATURE_COMPAT_RESIZE_INODE	0x0010
+#define EXT2_FEATURE_COMPAT_DIR_INDEX		0x0020
+/* Superblock filesystem feature flags (RO compatible) */
+#define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER	0x0001
+#define EXT2_FEATURE_RO_COMPAT_LARGE_FILE	0x0002
+#define EXT2_FEATURE_RO_COMPAT_BTREE_DIR	0x0004
+#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM		0x0010
+#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK	0x0020
+#define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE	0x0040
+/* Superblock filesystem feature flags (back-incompatible) */
+#define EXT2_FEATURE_INCOMPAT_COMPRESSION	0x0001
+#define EXT2_FEATURE_INCOMPAT_FILETYPE		0x0002
+#define EXT3_FEATURE_INCOMPAT_RECOVER		0x0004 /* Needs recovery */
+#define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV	0x0008 /* Journal device */
+#define EXT2_FEATURE_INCOMPAT_META_BG		0x0010
+#define EXT4_FEATURE_INCOMPAT_EXTENTS		0x0040 /* extents support */
+#define EXT4_FEATURE_INCOMPAT_64BIT		0x0080
+#define EXT4_FEATURE_INCOMPAT_FLEX_BG		0x0200
 
+/* The set of back-incompatible features this driver DOES support. Add (OR)
+ * flags here as the related features are implemented into the driver */
+#define EXT2_DRIVER_SUPPORTED_INCOMPAT ( EXT2_FEATURE_INCOMPAT_FILETYPE )
+/* The set of back-incompatible features this driver DOES NOT support but are
+ * ignored for some hackish reason. Flags here should be here _temporarily_!
+ * Remember that INCOMPAT_* features are so for a reason! */
+#define EXT2_DRIVER_IGNORED_INCOMPAT ( EXT3_FEATURE_INCOMPAT_RECOVER )
+
+/* Strings for the driver environment options */
+#define EXT2_DRIVER_ENVOPT_VAR "ext2_options"
+#define EXT2_DRIVER_ENVOPT_IGNOREINCOMPAT "ignore_incompatible"
+
 #define EXT3_JOURNAL_MAGIC_NUMBER	0xc03b3998U
 
 #define EXT3_JOURNAL_DESCRIPTOR_BLOCK	1
@@ -379,6 +414,7 @@
 grub_ext2_mount (grub_disk_t disk)
 {
   struct grub_ext2_data *data;
+  char* env_options = grub_env_get (EXT2_DRIVER_ENVOPT_VAR);
 
   data = grub_malloc (sizeof (struct grub_ext2_data));
   if (!data)
@@ -394,6 +430,14 @@
   if (grub_le_to_cpu16 (data->sblock.magic) != EXT2_MAGIC)
     goto fail;
   
+  /* Check the FS doesn't have feature bits enabled that we don't support.
+   * Ignore this check if the "ignore_incompatible" env. option is set */
+  if (0 != (grub_le_to_cpu32 (data->sblock.feature_incompat)
+        & ~(EXT2_DRIVER_SUPPORTED_INCOMPAT | EXT2_DRIVER_IGNORED_INCOMPAT))
+      && (0 == grub_strstr (env_options, EXT2_DRIVER_ENVOPT_IGNOREINCOMPAT)))
+    goto fail;
+    
+  
   data->disk = disk;
 
   data->diropen.data = data;
@@ -409,7 +453,8 @@
   return data;
 
  fail:
-  grub_error (GRUB_ERR_BAD_FS, "not an ext2 filesystem");
+  grub_error (GRUB_ERR_BAD_FS, "not an ext2 filesystem, or incompatible"
+                               "features enabled (extents, etc.)");
   grub_free (data);
   return 0;
 }