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METADATA_CSUM: superblock checksum added.

--- a/lwext4/ext4_config.h

+++ b/lwext4/ext4_config.h

@@ -153,6 +153,11 @@

 #endif

 #endif

+#ifndef ext4_offsetof

+#define ext4_offsetof(type, field) \

+	((long)(&(((type *)0)->field)))

+#endif

+

 #endif /* EXT4_CONFIG_H_ */

 /**

--- a/lwext4/ext4_mkfs.c

+++ b/lwext4/ext4_mkfs.c

@@ -259,7 +259,7 @@

 	sb->last_orphan = 0;

 	sb->hash_seed[0] = 0; /* FIXME */

 	sb->default_hash_version = EXT2_HTREE_HALF_MD4;

-	sb->reserved_char_pad = 1;

+	sb->checksum_type = 1;

 	sb->desc_size = EXT4_MIN_BLOCK_GROUP_DESCRIPTOR_SIZE;

 	sb->default_mount_opts = 0; /* FIXME */

 	sb->first_meta_bg = 0;

--- a/lwext4/ext4_super.c

+++ b/lwext4/ext4_super.c

@@ -41,6 +41,7 @@

 #include "ext4_config.h"

 #include "ext4_super.h"

+#include "ext4_crc32c.h"

 uint32_t ext4_block_group_cnt(struct ext4_sblock *s)

 {

@@ -79,8 +80,36 @@

 	return (total_inodes - ((block_group_count - 1) * inodes_per_group));

 }

+static uint32_t ext4_sb_csum(struct ext4_sblock *s)

+{

+	return ext4_crc32c(~0, s,

+			ext4_offsetof(struct ext4_sblock, checksum));

+}

+

+static bool ext4_sb_verify_csum(struct ext4_sblock *s)

+{

+	if (!ext4_sb_has_feature_read_only(s,

+					   EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM))

+		return true;

+

+	if (s->checksum_type != to_le32(EXT4_CHECKSUM_CRC32C))

+		return false;

+

+	return s->checksum == to_le32(ext4_sb_csum(s));

+}

+

+static void ext4_sb_set_csum(struct ext4_sblock *s)

+{

+	if (!ext4_sb_has_feature_read_only(s,

+					   EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM))

+		return;

+

+	s->checksum = to_le32(ext4_sb_csum(s));

+}

+

 int ext4_sb_write(struct ext4_blockdev *bdev, struct ext4_sblock *s)

 {

+	ext4_sb_set_csum(s);

 	return ext4_block_writebytes(bdev, EXT4_SUPERBLOCK_OFFSET, s,

 				     EXT4_SUPERBLOCK_SIZE);

 }

@@ -118,6 +147,9 @@

 		return false;

 	if (ext4_sb_get_desc_size(s) > EXT4_MAX_BLOCK_GROUP_DESCRIPTOR_SIZE)

+		return false;

+

+	if (!ext4_sb_verify_csum(s))

 		return false;

 	return true;

--- a/lwext4/ext4_types.h

+++ b/lwext4/ext4_types.h

@@ -48,6 +48,8 @@

 #include <stdint.h>

+#define EXT4_CHECKSUM_CRC32C 1

+

 /*

  * Structure of the super block

  */

@@ -126,7 +128,7 @@

 	uint64_t mmp_block;	  /* Block for multi-mount protection */

 	uint32_t raid_stripe_width;  /* Blocks on all data disks (N * stride) */

 	uint8_t log_groups_per_flex; /* FLEX_BG group size */

-	uint8_t reserved_char_pad;

+	uint8_t checksum_type;

 	uint16_t reserved_pad;

 	uint64_t kbytes_written; /* Number of lifetime kilobytes written */

 	uint32_t snapshot_inum;  /* I-node number of active snapshot */

@@ -149,7 +151,15 @@

 	uint64_t last_error_block;    /* Block involved of last error */

 	uint8_t last_error_func[32];  /* Function where the error happened */

 	uint8_t mount_opts[64];

-	uint32_t padding[112]; /* Padding to the end of the block */

+	uint32_t usr_quota_inum;	/* inode for tracking user quota */

+	uint32_t grp_quota_inum;	/* inode for tracking group quota */

+	uint32_t overhead_clusters;	/* overhead blocks/clusters in fs */

+	uint32_t backup_bgs[2];	/* groups with sparse_super2 SBs */

+	uint8_t  encrypt_algos[4];	/* Encryption algorithms in use  */

+	uint8_t  encrypt_pw_salt[16];	/* Salt used for string2key algorithm */

+	uint32_t lpf_ino;		/* Location of the lost+found inode */

+	uint32_t padding[100];	/* Padding to the end of the block */

+	uint32_t checksum;		/* crc32c(superblock) */

 } __attribute__((packed));

 #define EXT4_SUPERBLOCK_MAGIC 0xEF53