7 files changed, 335 insertions, 35 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index d8062745716a..e31f3691b151 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -140,6 +140,7 @@ config EXT4DEV_FS
         tristate "Ext4dev/ext4 extended fs support development (EXPERIMENTAL)"
         depends on EXPERIMENTAL
         select JBD2
+        select CRC16
         help
           Ext4dev is a predecessor filesystem of the next generation
           extended fs ext4, based on ext3 filesystem code. It will be
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index b74bf4368441..5927687b3e79 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -20,6 +20,7 @@
 #include <linux/quotaops.h>
 #include <linux/buffer_head.h>
 
+#include "group.h"
 /*
  * balloc.c contains the blocks allocation and deallocation routines
  */
@@ -42,6 +43,94 @@ void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
 
 }
 
+/* Initializes an uninitialized block bitmap if given, and returns the
+ * number of blocks free in the group. */
+unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
+                                int block_group, struct ext4_group_desc *gdp)
+{
+        unsigned long start;
+        int bit, bit_max;
+        unsigned free_blocks, group_blocks;
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+        if (bh) {
+                J_ASSERT_BH(bh, buffer_locked(bh));
+
+                /* If checksum is bad mark all blocks used to prevent allocation
+                 * essentially implementing a per-group read-only flag. */
+                if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
+                        ext4_error(sb, __FUNCTION__,
+                                   "Checksum bad for group %u\n", block_group);
+                        gdp->bg_free_blocks_count = 0;
+                        gdp->bg_free_inodes_count = 0;
+                        gdp->bg_itable_unused = 0;
+                        memset(bh->b_data, 0xff, sb->s_blocksize);
+                        return 0;
+                }
+                memset(bh->b_data, 0, sb->s_blocksize);
+        }
+
+        /* Check for superblock and gdt backups in this group */
+        bit_max = ext4_bg_has_super(sb, block_group);
+
+        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
+            block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
+                          sbi->s_desc_per_block) {
+                if (bit_max) {
+                        bit_max += ext4_bg_num_gdb(sb, block_group);
+                        bit_max +=
+                                le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
+                }
+        } else { /* For META_BG_BLOCK_GROUPS */
+                int group_rel = (block_group -
+                                 le32_to_cpu(sbi->s_es->s_first_meta_bg)) %
+                                EXT4_DESC_PER_BLOCK(sb);
+                if (group_rel == 0 || group_rel == 1 ||
+                    (group_rel == EXT4_DESC_PER_BLOCK(sb) - 1))
+                        bit_max += 1;
+        }
+
+        if (block_group == sbi->s_groups_count - 1) {
+                /*
+                 * Even though mke2fs always initialize first and last group
+                 * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
+                 * to make sure we calculate the right free blocks
+                 */
+                group_blocks = ext4_blocks_count(sbi->s_es) -
+                        le32_to_cpu(sbi->s_es->s_first_data_block) -
+                        (EXT4_BLOCKS_PER_GROUP(sb) * (sbi->s_groups_count -1));
+        } else {
+                group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
+        }
+
+        free_blocks = group_blocks - bit_max;
+
+        if (bh) {
+                for (bit = 0; bit < bit_max; bit++)
+                        ext4_set_bit(bit, bh->b_data);
+
+                start = block_group * EXT4_BLOCKS_PER_GROUP(sb) +
+                        le32_to_cpu(sbi->s_es->s_first_data_block);
+
+                /* Set bits for block and inode bitmaps, and inode table */
+                ext4_set_bit(ext4_block_bitmap(sb, gdp) - start, bh->b_data);
+                ext4_set_bit(ext4_inode_bitmap(sb, gdp) - start, bh->b_data);
+                for (bit = le32_to_cpu(gdp->bg_inode_table) - start,
+                     bit_max = bit + sbi->s_itb_per_group; bit < bit_max; bit++)
+                        ext4_set_bit(bit, bh->b_data);
+
+                /*
+                 * Also if the number of blocks within the group is
+                 * less than the blocksize * 8 ( which is the size
+                 * of bitmap ), set rest of the block bitmap to 1
+                 */
+                mark_bitmap_end(group_blocks, sb->s_blocksize * 8, bh->b_data);
+        }
+
+        return free_blocks - sbi->s_itb_per_group - 2;
+}
+
+
 /*
  * The free blocks are managed by bitmaps.  A file system contains several
  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
@@ -119,7 +208,7 @@ block_in_use(ext4_fsblk_t block, struct super_block *sb, unsigned char *map)
  *
  * Return buffer_head on success or NULL in case of failure.
  */
-static struct buffer_head *
+struct buffer_head *
 read_block_bitmap(struct super_block *sb, unsigned int block_group)
 {
         int i;
@@ -127,11 +216,24 @@ read_block_bitmap(struct super_block *sb, unsigned int block_group)
         struct buffer_head * bh = NULL;
         ext4_fsblk_t bitmap_blk;
 
-        desc = ext4_get_group_desc (sb, block_group, NULL);
+        desc = ext4_get_group_desc(sb, block_group, NULL);
         if (!desc)
                 return NULL;
         bitmap_blk = ext4_block_bitmap(sb, desc);
-        bh = sb_bread(sb, bitmap_blk);
+        if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
+                bh = sb_getblk(sb, bitmap_blk);
+                if (!buffer_uptodate(bh)) {
+                        lock_buffer(bh);
+                        if (!buffer_uptodate(bh)) {
+                                ext4_init_block_bitmap(sb, bh, block_group,
+                                                       desc);
+                                set_buffer_uptodate(bh);
+                        }
+                        unlock_buffer(bh);
+                }
+        } else {
+                bh = sb_bread(sb, bitmap_blk);
+        }
         if (!bh)
                 ext4_error (sb, __FUNCTION__,
                             "Cannot read block bitmap - "
@@ -627,6 +729,7 @@ do_more:
         desc->bg_free_blocks_count =
                 cpu_to_le16(le16_to_cpu(desc->bg_free_blocks_count) +
                         group_freed);
+        desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
         spin_unlock(sb_bgl_lock(sbi, block_group));
         percpu_counter_add(&sbi->s_freeblocks_counter, count);
 
@@ -1685,8 +1788,11 @@ allocated:
                         ret_block, goal_hits, goal_attempts);
 
         spin_lock(sb_bgl_lock(sbi, group_no));
+        if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))
+                gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
         gdp->bg_free_blocks_count =
                         cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)-num);
+        gdp->bg_checksum = ext4_group_desc_csum(sbi, group_no, gdp);
         spin_unlock(sb_bgl_lock(sbi, group_no));
         percpu_counter_sub(&sbi->s_freeblocks_counter, num);
 
diff --git a/fs/ext4/group.h b/fs/ext4/group.h
new file mode 100644
index 000000000000..1577910bb58b
--- /dev/null
+++ b/fs/ext4/group.h
@@ -0,0 +1,27 @@
+/*
+ *  linux/fs/ext4/group.h
+ *
+ * Copyright (C) 2007 Cluster File Systems, Inc
+ *
+ * Author: Andreas Dilger <adilger@clusterfs.com>
+ */
+
+#ifndef _LINUX_EXT4_GROUP_H
+#define _LINUX_EXT4_GROUP_H
+
+extern __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 group,
+                                   struct ext4_group_desc *gdp);
+extern int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 group,
+                                       struct ext4_group_desc *gdp);
+struct buffer_head *read_block_bitmap(struct super_block *sb,
+                                      unsigned int block_group);
+extern unsigned ext4_init_block_bitmap(struct super_block *sb,
+                                       struct buffer_head *bh, int group,
+                                       struct ext4_group_desc *desc);
+#define ext4_free_blocks_after_init(sb, group, desc)                    \
+                ext4_init_block_bitmap(sb, NULL, group, desc)
+extern unsigned ext4_init_inode_bitmap(struct super_block *sb,
+                                       struct buffer_head *bh, int group,
+                                       struct ext4_group_desc *desc);
+extern void mark_bitmap_end(int start_bit, int end_bit, char *bitmap);
+#endif /* _LINUX_EXT4_GROUP_H */
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 38e9a0a705df..c61f37fd3f05 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -28,6 +28,7 @@
 
 #include "xattr.h"
 #include "acl.h"
+#include "group.h"
 
 /*
  * ialloc.c contains the inodes allocation and deallocation routines
@@ -43,6 +44,52 @@
  * the free blocks count in the block.
  */
 
+/*
+ * To avoid calling the atomic setbit hundreds or thousands of times, we only
+ * need to use it within a single byte (to ensure we get endianness right).
+ * We can use memset for the rest of the bitmap as there are no other users.
+ */
+void mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
+{
+        int i;
+
+        if (start_bit >= end_bit)
+                return;
+
+        ext4_debug("mark end bits +%d through +%d used\n", start_bit, end_bit);
+        for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
+                ext4_set_bit(i, bitmap);
+        if (i < end_bit)
+                memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
+}
+
+/* Initializes an uninitialized inode bitmap */
+unsigned ext4_init_inode_bitmap(struct super_block *sb,
+                                struct buffer_head *bh, int block_group,
+                                struct ext4_group_desc *gdp)
+{
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+        J_ASSERT_BH(bh, buffer_locked(bh));
+
+        /* If checksum is bad mark all blocks and inodes use to prevent
+         * allocation, essentially implementing a per-group read-only flag. */
+        if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
+                ext4_error(sb, __FUNCTION__, "Checksum bad for group %u\n",
+                           block_group);
+                gdp->bg_free_blocks_count = 0;
+                gdp->bg_free_inodes_count = 0;
+                gdp->bg_itable_unused = 0;
+                memset(bh->b_data, 0xff, sb->s_blocksize);
+                return 0;
+        }
+
+        memset(bh->b_data, 0, (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
+        mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), EXT4_BLOCKS_PER_GROUP(sb),
+                        bh->b_data);
+
+        return EXT4_INODES_PER_GROUP(sb);
+}
 
 /*
  * Read the inode allocation bitmap for a given block_group, reading
@@ -59,8 +106,20 @@ read_inode_bitmap(struct super_block * sb, unsigned long block_group)
         desc = ext4_get_group_desc(sb, block_group, NULL);
         if (!desc)
                 goto error_out;
-
-        bh = sb_bread(sb, ext4_inode_bitmap(sb, desc));
+        if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
+                bh = sb_getblk(sb, ext4_inode_bitmap(sb, desc));
+                if (!buffer_uptodate(bh)) {
+                        lock_buffer(bh);
+                        if (!buffer_uptodate(bh)) {
+                                ext4_init_inode_bitmap(sb, bh, block_group,
+                                                       desc);
+                                set_buffer_uptodate(bh);
+                        }
+                        unlock_buffer(bh);
+                }
+        } else {
+                bh = sb_bread(sb, ext4_inode_bitmap(sb, desc));
+        }
         if (!bh)
                 ext4_error(sb, "read_inode_bitmap",
                             "Cannot read inode bitmap - "
@@ -169,6 +228,8 @@ void ext4_free_inode (handle_t *handle, struct inode * inode)
                         if (is_directory)
                                 gdp->bg_used_dirs_count = cpu_to_le16(
                                   le16_to_cpu(gdp->bg_used_dirs_count) - 1);
+                        gdp->bg_checksum = ext4_group_desc_csum(sbi,
+                                                        block_group, gdp);
                         spin_unlock(sb_bgl_lock(sbi, block_group));
                         percpu_counter_inc(&sbi->s_freeinodes_counter);
                         if (is_directory)
@@ -435,7 +496,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode * dir, int mode)
         struct ext4_sb_info *sbi;
         int err = 0;
         struct inode *ret;
-        int i;
+        int i, free = 0;
 
         /* Cannot create files in a deleted directory */
         if (!dir || !dir->i_nlink)
@@ -517,11 +578,13 @@ repeat_in_this_group:
         goto out;
 
 got:
-        ino += group * EXT4_INODES_PER_GROUP(sb) + 1;
-        if (ino < EXT4_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
-                ext4_error (sb, "ext4_new_inode",
-                            "reserved inode or inode > inodes count - "
-                            "block_group = %d, inode=%lu", group, ino);
+        ino++;
+        if ((group == 0 && ino < EXT4_FIRST_INO(sb)) ||
+            ino > EXT4_INODES_PER_GROUP(sb)) {
+                ext4_error(sb, __FUNCTION__,
+                           "reserved inode or inode > inodes count - "
+                           "block_group = %d, inode=%lu", group,
+                           ino + group * EXT4_INODES_PER_GROUP(sb));
                 err = -EIO;
                 goto fail;
         }
@@ -529,13 +592,78 @@ got:
         BUFFER_TRACE(bh2, "get_write_access");
         err = ext4_journal_get_write_access(handle, bh2);
         if (err) goto fail;
+
+        /* We may have to initialize the block bitmap if it isn't already */
+        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
+            gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
+                struct buffer_head *block_bh = read_block_bitmap(sb, group);
+
+                BUFFER_TRACE(block_bh, "get block bitmap access");
+                err = ext4_journal_get_write_access(handle, block_bh);
+                if (err) {
+                        brelse(block_bh);
+                        goto fail;
+                }
+
+                free = 0;
+                spin_lock(sb_bgl_lock(sbi, group));
+                /* recheck and clear flag under lock if we still need to */
+                if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
+                        gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
+                        free = ext4_free_blocks_after_init(sb, group, gdp);
+                        gdp->bg_free_blocks_count = cpu_to_le16(free);
+                }
+                spin_unlock(sb_bgl_lock(sbi, group));
+
+                /* Don't need to dirty bitmap block if we didn't change it */
+                if (free) {
+                        BUFFER_TRACE(block_bh, "dirty block bitmap");
+                        err = ext4_journal_dirty_metadata(handle, block_bh);
+                }
+
+                brelse(block_bh);
+                if (err)
+                        goto fail;
+        }
+
         spin_lock(sb_bgl_lock(sbi, group));
+        /* If we didn't allocate from within the initialized part of the inode
+         * table then we need to initialize up to this inode. */
+        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+                if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
+                        gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
+
+                        /* When marking the block group with
+                         * ~EXT4_BG_INODE_UNINIT we don't want to depend
+                         * on the value of bg_itable_unsed even though
+                         * mke2fs could have initialized the same for us.
+                         * Instead we calculated the value below
+                         */
+
+                        free = 0;
+                } else {
+                        free = EXT4_INODES_PER_GROUP(sb) -
+                                le16_to_cpu(gdp->bg_itable_unused);
+                }
+
+                /*
+                 * Check the relative inode number against the last used
+                 * relative inode number in this group. if it is greater
+                 * we need to  update the bg_itable_unused count
+                 *
+                 */
+                if (ino > free)
+                        gdp->bg_itable_unused =
+                                cpu_to_le16(EXT4_INODES_PER_GROUP(sb) - ino);
+        }
+
         gdp->bg_free_inodes_count =
                 cpu_to_le16(le16_to_cpu(gdp->bg_free_inodes_count) - 1);
         if (S_ISDIR(mode)) {
                 gdp->bg_used_dirs_count =
                         cpu_to_le16(le16_to_cpu(gdp->bg_used_dirs_count) + 1);
         }
+        gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
         spin_unlock(sb_bgl_lock(sbi, group));
         BUFFER_TRACE(bh2, "call ext4_journal_dirty_metadata");
         err = ext4_journal_dirty_metadata(handle, bh2);
@@ -557,7 +685,7 @@ got:
                 inode->i_gid = current->fsgid;
         inode->i_mode = mode;
 
-        inode->i_ino = ino;
+        inode->i_ino = ino + group * EXT4_INODES_PER_GROUP(sb);
         /* This is the optimal IO size (for stat), not the fs block size */
         inode->i_blocks = 0;
         inode->i_mtime = inode->i_atime = inode->i_ctime = ei->i_crtime =
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 472fc0d3e1c0..0a7e914c495a 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -16,6 +16,7 @@
 #include <linux/errno.h>
 #include <linux/slab.h>
 
+#include "group.h"
 
 #define outside(b, first, last) ((b) < (first) || (b) >= (last))
 #define inside(b, first, last)  ((b) >= (first) && (b) < (last))
@@ -140,25 +141,6 @@ static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
 }
 
 /*
- * To avoid calling the atomic setbit hundreds or thousands of times, we only
- * need to use it within a single byte (to ensure we get endianness right).
- * We can use memset for the rest of the bitmap as there are no other users.
- */
-static void mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
-{
-        int i;
-
-        if (start_bit >= end_bit)
-                return;
-
-        ext4_debug("mark end bits +%d through +%d used\n", start_bit, end_bit);
-        for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
-                ext4_set_bit(i, bitmap);
-        if (i < end_bit)
-                memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
-}
-
-/*
  * Set up the block and inode bitmaps, and the inode table for the new group.
  * This doesn't need to be part of the main transaction, since we are only
  * changing blocks outside the actual filesystem.  We still do journaling to
@@ -842,6 +824,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
         ext4_inode_table_set(sb, gdp, input->inode_table); /* LV FIXME */
         gdp->bg_free_blocks_count = cpu_to_le16(input->free_blocks_count);
         gdp->bg_free_inodes_count = cpu_to_le16(EXT4_INODES_PER_GROUP(sb));
+        gdp->bg_checksum = ext4_group_desc_csum(sbi, input->group, gdp);
 
         /*
          * Make the new blocks and inodes valid next.  We do this before
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e2bdf93693a6..dd4ff9c87358 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -37,12 +37,14 @@
 #include <linux/quotaops.h>
 #include <linux/seq_file.h>
 #include <linux/log2.h>
+#include <linux/crc16.h>
 
 #include <asm/uaccess.h>
 
 #include "xattr.h"
 #include "acl.h"
 #include "namei.h"
+#include "group.h"
 
 static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
                              unsigned long journal_devnum);
@@ -1308,6 +1310,43 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
         return res;
 }
 
+__le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
+                            struct ext4_group_desc *gdp)
+{
+        __u16 crc = 0;
+
+        if (sbi->s_es->s_feature_ro_compat &
+            cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+                int offset = offsetof(struct ext4_group_desc, bg_checksum);
+                __le32 le_group = cpu_to_le32(block_group);
+
+                crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
+                crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
+                crc = crc16(crc, (__u8 *)gdp, offset);
+                offset += sizeof(gdp->bg_checksum); /* skip checksum */
+                /* for checksum of struct ext4_group_desc do the rest...*/
+                if ((sbi->s_es->s_feature_incompat &
+                     cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
+                    offset < le16_to_cpu(sbi->s_es->s_desc_size))
+                        crc = crc16(crc, (__u8 *)gdp + offset,
+                                    le16_to_cpu(sbi->s_es->s_desc_size) -
+                                        offset);
+        }
+
+        return cpu_to_le16(crc);
+}
+
+int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 block_group,
+                                struct ext4_group_desc *gdp)
+{
+        if ((sbi->s_es->s_feature_ro_compat &
+             cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) &&
+            (gdp->bg_checksum != ext4_group_desc_csum(sbi, block_group, gdp)))
+                return 0;
+
+        return 1;
+}
+
 /* Called at mount-time, super-block is locked */
 static int ext4_check_descriptors (struct super_block * sb)
 {
@@ -1362,6 +1401,14 @@ static int ext4_check_descriptors (struct super_block * sb)
                                     i, inode_table);
                         return 0;
                 }
+                if (!ext4_group_desc_csum_verify(sbi, i, gdp)) {
+                        ext4_error(sb, __FUNCTION__,
+                                   "Checksum for group %d failed (%u!=%u)\n", i,
+                                   le16_to_cpu(ext4_group_desc_csum(sbi, i,
+                                                                    gdp)),
+                                   le16_to_cpu(gdp->bg_checksum));
+                        return 0;
+                }
                 first_block += EXT4_BLOCKS_PER_GROUP(sb);
                 gdp = (struct ext4_group_desc *)
                         ((__u8 *)gdp + EXT4_DESC_SIZE(sb));
diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 151738af6be2..b77b59fe7f56 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -105,19 +105,25 @@
  */
 struct ext4_group_desc
 {
-        __le32  bg_block_bitmap;                /* Blocks bitmap block */
-        __le32  bg_inode_bitmap;                /* Inodes bitmap block */
+        __le32  bg_block_bitmap;        /* Blocks bitmap block */
+        __le32  bg_inode_bitmap;        /* Inodes bitmap block */
         __le32  bg_inode_table;         /* Inodes table block */
         __le16  bg_free_blocks_count;   /* Free blocks count */
         __le16  bg_free_inodes_count;   /* Free inodes count */
         __le16  bg_used_dirs_count;     /* Directories count */
-        __u16   bg_flags;
-        __u32   bg_reserved[3];
+        __le16  bg_flags;               /* EXT4_BG_flags (INODE_UNINIT, etc) */
+        __u32   bg_reserved[2];         /* Likely block/inode bitmap checksum */
+        __le16  bg_itable_unused;       /* Unused inodes count */
+        __le16  bg_checksum;            /* crc16(sb_uuid+group+desc) */
         __le32  bg_block_bitmap_hi;     /* Blocks bitmap block MSB */
         __le32  bg_inode_bitmap_hi;     /* Inodes bitmap block MSB */
         __le32  bg_inode_table_hi;      /* Inodes table block MSB */
 };
 
+#define EXT4_BG_INODE_UNINIT    0x0001 /* Inode table/bitmap not in use */
+#define EXT4_BG_BLOCK_UNINIT    0x0002 /* Block bitmap not in use */
+#define EXT4_BG_INODE_ZEROED    0x0004 /* On-disk itable initialized to zero */
+
 #ifdef __KERNEL__
 #include <linux/ext4_fs_i.h>
 #include <linux/ext4_fs_sb.h>
@@ -665,6 +671,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 #define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER     0x0001
 #define EXT4_FEATURE_RO_COMPAT_LARGE_FILE       0x0002
 #define EXT4_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
 
@@ -684,6 +691,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
                                          EXT4_FEATURE_INCOMPAT_64BIT)
 #define EXT4_FEATURE_RO_COMPAT_SUPP     (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
                                          EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
+                                         EXT4_FEATURE_RO_COMPAT_GDT_CSUM| \
                                          EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \
                                          EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE | \
                                          EXT4_FEATURE_RO_COMPAT_BTREE_DIR)