5 files changed, 31 insertions, 11 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index df77ea891f29..3dacb124b8c8 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -74,10 +74,12 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
                 return NULL;
         }
 
-        desc = (struct ext4_group_desc *) sbi->s_group_desc[group_desc]->b_data;
+        desc = (struct ext4_group_desc *)(
+                (__u8 *)sbi->s_group_desc[group_desc]->b_data +
+                offset * EXT4_DESC_SIZE(sb));
         if (bh)
                 *bh = sbi->s_group_desc[group_desc];
-        return desc + offset;
+        return desc;
 }
 
 /**
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c05dc57148bb..d03e7d85a638 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2432,14 +2432,16 @@ static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb,
                 return 0;
         }
 
-        gdp = (struct ext4_group_desc *)bh->b_data;
+        gdp = (struct ext4_group_desc *)((__u8 *)bh->b_data +
+                desc * EXT4_DESC_SIZE(sb));
         /*
          * Figure out the offset within the block group inode table
          */
         offset = ((ino - 1) % EXT4_INODES_PER_GROUP(sb)) *
                 EXT4_INODE_SIZE(sb);
-        block = ext4_inode_table(gdp + desc) +
-                        (offset >> EXT4_BLOCK_SIZE_BITS(sb));
+        block = ext4_inode_table(gdp) + (offset >> EXT4_BLOCK_SIZE_BITS(sb));
+
+
 
         iloc->block_group = block_group;
         iloc->offset = offset & (EXT4_BLOCK_SIZE(sb) - 1);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d844175e60e8..bc8848bff2f1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1268,7 +1268,8 @@ static int ext4_check_descriptors (struct super_block * sb)
                         return 0;
                 }
                 first_block += EXT4_BLOCKS_PER_GROUP(sb);
-                gdp++;
+                gdp = (struct ext4_group_desc *)
+                        ((__u8 *)gdp + EXT4_DESC_SIZE(sb));
         }
 
         ext4_free_blocks_count_set(sbi->s_es, ext4_count_free_blocks(sb));
@@ -1619,7 +1620,18 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
                        sbi->s_frag_size, blocksize);
                 goto failed_mount;
         }
-        sbi->s_frags_per_block = 1;
+        sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
+        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_64BIT)) {
+                if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE ||
+                    sbi->s_desc_size > EXT4_MAX_DESC_SIZE ||
+                    sbi->s_desc_size & (sbi->s_desc_size - 1)) {
+                        printk(KERN_ERR
+                               "EXT4-fs: unsupported descriptor size %ld\n",
+                               sbi->s_desc_size);
+                        goto failed_mount;
+                }
+        } else
+                sbi->s_desc_size = EXT4_MIN_DESC_SIZE;
         sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
         sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
         sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
@@ -1630,7 +1642,7 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
                 goto cantfind_ext4;
         sbi->s_itb_per_group = sbi->s_inodes_per_group /
                                         sbi->s_inodes_per_block;
-        sbi->s_desc_per_block = blocksize / sizeof(struct ext4_group_desc);
+        sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
         sbi->s_sbh = bh;
         sbi->s_mount_state = le16_to_cpu(es->s_state);
         sbi->s_addr_per_block_bits = log2(EXT4_ADDR_PER_BLOCK(sb));
diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 8e5009ee4ad8..a3df2afc004b 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -142,6 +142,9 @@ struct ext4_group_desc
 /*
  * Macro-instructions used to manage group descriptors
  */
+#define EXT4_MIN_DESC_SIZE              32
+#define EXT4_MAX_DESC_SIZE              EXT4_MIN_BLOCK_SIZE
+#define EXT4_DESC_SIZE(s)               (EXT4_SB(s)->s_desc_size)
 #ifdef __KERNEL__
 # define EXT4_BLOCKS_PER_GROUP(s)       (EXT4_SB(s)->s_blocks_per_group)
 # define EXT4_DESC_PER_BLOCK(s)         (EXT4_SB(s)->s_desc_per_block)
@@ -149,7 +152,7 @@ struct ext4_group_desc
 # define EXT4_DESC_PER_BLOCK_BITS(s)    (EXT4_SB(s)->s_desc_per_block_bits)
 #else
 # define EXT4_BLOCKS_PER_GROUP(s)       ((s)->s_blocks_per_group)
-# define EXT4_DESC_PER_BLOCK(s)         (EXT4_BLOCK_SIZE(s) / sizeof (struct ext4_group_desc))
+# define EXT4_DESC_PER_BLOCK(s)         (EXT4_BLOCK_SIZE(s) / EXT4_DESC_SIZE(s))
 # define EXT4_INODES_PER_GROUP(s)       ((s)->s_inodes_per_group)
 #endif
 
@@ -474,7 +477,7 @@ struct ext4_super_block {
          * things it doesn't understand...
          */
         __le32  s_first_ino;            /* First non-reserved inode */
-        __le16   s_inode_size;          /* size of inode structure */
+        __le16  s_inode_size;           /* size of inode structure */
         __le16  s_block_group_nr;       /* block group # of this superblock */
         __le32  s_feature_compat;       /* compatible feature set */
 /*60*/  __le32  s_feature_incompat;     /* incompatible feature set */
@@ -500,7 +503,7 @@ struct ext4_super_block {
         __le32  s_hash_seed[4];         /* HTREE hash seed */
         __u8    s_def_hash_version;     /* Default hash version to use */
         __u8    s_reserved_char_pad;
-        __u16   s_reserved_word_pad;
+        __le16  s_desc_size;            /* size of group descriptor */
 /*100*/ __le32  s_default_mount_opts;
         __le32  s_first_meta_bg;        /* First metablock block group */
         __le32  s_mkfs_time;            /* When the filesystem was created */
diff --git a/include/linux/ext4_fs_sb.h b/include/linux/ext4_fs_sb.h
index ce7a844d6703..691a713139ce 100644
--- a/include/linux/ext4_fs_sb.h
+++ b/include/linux/ext4_fs_sb.h
@@ -29,6 +29,7 @@
  */
 struct ext4_sb_info {
         unsigned long s_frag_size;      /* Size of a fragment in bytes */
+        unsigned long s_desc_size;      /* Size of a group descriptor in bytes */
         unsigned long s_frags_per_block;/* Number of fragments per block */
         unsigned long s_inodes_per_block;/* Number of inodes per block */
         unsigned long s_frags_per_group;/* Number of fragments in a group */