Re: [PATCH 1/2] libext2fs: add metadata checksum and snapshot feature flags

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On Thu, Sep 15, 2011 at 06:50:51PM -0400, Theodore Ts'o wrote:
> Reserve EXT4_FEATURE_RO_COMPAT_METADATA_CSUM and
> EXT2_FEATURE_COMPAT_EXCLUDE_BITMAP.  Also reserve fields in the
> superblock and the inode for the checksums.  In the block group
> descriptor, reserve the exclude bitmap field for the snapshot feature,
> and checksums for the inode and block allocation bitmaps.
> 
> With this commit, the metadata checksum and exclude bitmap features
> should have reserved all of the fields they need in ext4's on-disk
> format.
> 
> This commit also fixes an a missing byte swap for s_overhead_blocks.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
> Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
>  debugfs/set_fields.c        |    3 ++-
>  e2fsck/pass1.c              |    4 ++--
>  lib/e2p/feature.c           |    4 ++++
>  lib/e2p/ls.c                |    4 ++++
>  lib/ext2fs/ext2_fs.h        |   31 ++++++++++++++++++++++---------
>  lib/ext2fs/swapfs.c         |   16 ++++++++++++++--
>  lib/ext2fs/tst_inode_size.c |    3 ++-
>  lib/ext2fs/tst_super_size.c |    1 +
>  8 files changed, 51 insertions(+), 15 deletions(-)
> 
> diff --git a/debugfs/set_fields.c b/debugfs/set_fields.c
> index ac6bc25..1a5ec7f 100644
> --- a/debugfs/set_fields.c
> +++ b/debugfs/set_fields.c
> @@ -144,6 +144,7 @@ static struct field_set_info super_fields[] = {
>  	{ "usr_quota_inum", &set_sb.s_usr_quota_inum, 4, parse_uint },
>  	{ "grp_quota_inum", &set_sb.s_grp_quota_inum, 4, parse_uint },
>  	{ "overhead_blocks", &set_sb.s_overhead_blocks, 4, parse_uint },
> +	{ "checksum", &set_sb.s_checksum, 4, parse_uint },
>  	{ 0, 0, 0, 0 }
>  };
> 
> @@ -179,6 +180,7 @@ static struct field_set_info inode_fields[] = {
>  	{ "fsize", &set_inode.osd2.hurd2.h_i_fsize, 1, parse_uint },
>  	{ "uid_high", &set_inode.osd2.linux2.l_i_uid_high, 2, parse_uint },
>  	{ "gid_high", &set_inode.osd2.linux2.l_i_gid_high, 2, parse_uint },
> +	{ "checksum", &set_inode.osd2.linux2.l_i_checksum_lo, 2, parse_uint },
>  	{ "author", &set_inode.osd2.hurd2.h_i_author, 4, parse_uint },
>  	{ "bmap", NULL, 4, parse_bmap, FLAG_ARRAY },
>  	{ 0, 0, 0, 0 }
> @@ -192,7 +194,6 @@ static struct field_set_info ext2_bg_fields[] = {
>  	{ "free_inodes_count", &set_gd.bg_free_inodes_count, 2, parse_uint },
>  	{ "used_dirs_count", &set_gd.bg_used_dirs_count, 2, parse_uint },
>  	{ "flags", &set_gd.bg_flags, 2, parse_uint },
> -	{ "reserved", &set_gd.bg_reserved, 2, parse_uint, FLAG_ARRAY, 2 },
>  	{ "itable_unused", &set_gd.bg_itable_unused, 2, parse_uint },
>  	{ "checksum", &set_gd.bg_checksum, 2, parse_gd_csum },
>  	{ 0, 0, 0, 0 }
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index dd18ade..16ddcda 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -364,8 +364,8 @@ static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
>  	printf("inode #%u, i_extra_size %d\n", pctx->ino,
>  			inode->i_extra_isize);
>  #endif
> -	/* i_extra_isize must cover i_extra_isize + i_pad1 at least */
> -	min = sizeof(inode->i_extra_isize) + sizeof(inode->i_pad1);
> +	/* i_extra_isize must cover i_extra_isize + i_checksum_hi at least */
> +	min = sizeof(inode->i_extra_isize) + sizeof(inode->i_checksum_hi);
>  	max = EXT2_INODE_SIZE(sb) - EXT2_GOOD_OLD_INODE_SIZE;
>  	/*
>  	 * For now we will allow i_extra_isize to be 0, but really
> diff --git a/lib/e2p/feature.c b/lib/e2p/feature.c
> index 16fba53..965fc16 100644
> --- a/lib/e2p/feature.c
> +++ b/lib/e2p/feature.c
> @@ -40,6 +40,8 @@ static struct feature feature_list[] = {
>  			"resize_inode" },
>  	{	E2P_FEATURE_COMPAT, EXT2_FEATURE_COMPAT_LAZY_BG,
>  			"lazy_bg" },
> +	{	E2P_FEATURE_COMPAT, EXT2_FEATURE_COMPAT_EXCLUDE_BITMAP,
> +			"snapshot" },
> 
>  	{	E2P_FEATURE_RO_INCOMPAT, EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER,
>  			"sparse_super" },
> @@ -59,6 +61,8 @@ static struct feature feature_list[] = {
>  			"quota" },
>  	{	E2P_FEATURE_RO_INCOMPAT, EXT4_FEATURE_RO_COMPAT_BIGALLOC,
>  			"bigalloc"},
> +	{	E2P_FEATURE_RO_INCOMPAT, EXT4_FEATURE_RO_COMPAT_METADATA_CSUM,
> +			"metadata_csum"},
> 
>  	{	E2P_FEATURE_INCOMPAT, EXT2_FEATURE_INCOMPAT_COMPRESSION,
>  			"compression" },
> diff --git a/lib/e2p/ls.c b/lib/e2p/ls.c
> index 0f36f40..aaacdaa 100644
> --- a/lib/e2p/ls.c
> +++ b/lib/e2p/ls.c
> @@ -413,6 +413,10 @@ void list_super2(struct ext2_super_block * sb, FILE *f)
>  	if (sb->s_grp_quota_inum)
>  		fprintf(f, "Group quota inode:        %u\n",
>  			sb->s_grp_quota_inum);
> +
> +	if (sb->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)
> +		fprintf(f, "Checksum:                 0x%08x\n",
> +			sb->s_checksum);
>  }
> 
>  void list_super (struct ext2_super_block * s)
> diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
> index 4fec5db..1c86cb2 100644
> --- a/lib/ext2fs/ext2_fs.h
> +++ b/lib/ext2fs/ext2_fs.h
> @@ -142,7 +142,9 @@ struct ext2_group_desc
>  	__u16	bg_free_inodes_count;	/* Free inodes count */
>  	__u16	bg_used_dirs_count;	/* Directories count */
>  	__u16	bg_flags;
> -	__u32	bg_reserved[2];
> +	__u32	bg_exclude_bitmap_lo;	/* Exclude bitmap for snapshots */
> +	__u16	bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
> +	__u16	bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
>  	__u16	bg_itable_unused;	/* Unused inodes count */
>  	__u16	bg_checksum;		/* crc16(s_uuid+grouo_num+group_desc)*/
>  };
> @@ -159,7 +161,9 @@ struct ext4_group_desc
>  	__u16	bg_free_inodes_count;	/* Free inodes count */
>  	__u16	bg_used_dirs_count;	/* Directories count */
>  	__u16	bg_flags;		/* EXT4_BG_flags (INODE_UNINIT, etc) */
> -	__u32	bg_reserved[2];		/* Likely block/inode bitmap checksum */
> +	__u32	bg_exclude_bitmap_lo;	/* Exclude bitmap for snapshots */
> +	__u16	bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
> +	__u16	bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
>  	__u16	bg_itable_unused;	/* Unused inodes count */
>  	__u16	bg_checksum;		/* crc16(sb_uuid+group+desc) */
>  	__u32	bg_block_bitmap_hi;	/* Blocks bitmap block MSB */
> @@ -169,7 +173,10 @@ struct ext4_group_desc
>  	__u16	bg_free_inodes_count_hi;/* Free inodes count MSB */
>  	__u16	bg_used_dirs_count_hi;	/* Directories count MSB */
>  	__u16	bg_itable_unused_hi;	/* Unused inodes count MSB */
> -	__u32	bg_reserved2[3];
> +	__u32	bg_exclude_bitmap_hi;	/* Exclude bitmap block MSB */
> +	__u16	bg_block_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bitmap) MSB */
> +	__u16	bg_inode_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bitmap) MSB */
> +	__u32	bg_reserved;

Should we attach a checksum to the exclude bitmap?  That would, unfortunately,
put the 64-byte block group pretty close to full, unless we're ok with making
the bg even bigger...

--D
>  };
> 
>  #define EXT2_BG_INODE_UNINIT	0x0001 /* Inode table/bitmap not initialized */
> @@ -363,7 +370,8 @@ struct ext2_inode {
>  			__u16	l_i_file_acl_high;
>  			__u16	l_i_uid_high;	/* these 2 fields    */
>  			__u16	l_i_gid_high;	/* were reserved2[0] */
> -			__u32	l_i_reserved2;
> +			__u16	l_i_checksum_lo;	/* crc32c(uuid+inum+inode) */
> +			__u16	l_i_reserved;	/* crc32c(uuid+inum+inode) */
>  		} linux2;
>  		struct {
>  			__u8	h_i_frag;	/* Fragment number */
> @@ -410,7 +418,8 @@ struct ext2_inode_large {
>  			__u16	l_i_file_acl_high;
>  			__u16	l_i_uid_high;	/* these 2 fields    */
>  			__u16	l_i_gid_high;	/* were reserved2[0] */
> -			__u32	l_i_reserved2;
> +			__u16	l_i_checksum_lo; /* crc32c(uuid+inum+inode) */
> +			__u16	l_i_reserved;
>  		} linux2;
>  		struct {
>  			__u8	h_i_frag;	/* Fragment number */
> @@ -422,7 +431,7 @@ struct ext2_inode_large {
>  		} hurd2;
>  	} osd2;				/* OS dependent 2 */
>  	__u16	i_extra_isize;
> -	__u16	i_pad1;
> +	__u16	i_checksum_hi;	/* crc32c(uuid+inum+inode) */
>  	__u32	i_ctime_extra;	/* extra Change time (nsec << 2 | epoch) */
>  	__u32	i_mtime_extra;	/* extra Modification time (nsec << 2 | epoch) */
>  	__u32	i_atime_extra;	/* extra Access time (nsec << 2 | epoch) */
> @@ -441,7 +450,7 @@ struct ext2_inode_large {
>  #define i_gid_low	i_gid
>  #define i_uid_high	osd2.linux2.l_i_uid_high
>  #define i_gid_high	osd2.linux2.l_i_gid_high
> -#define i_reserved2	osd2.linux2.l_i_reserved2
> +#define i_checksum	osd2.linux2.l_i_checksum
>  #else
>  #if defined(__GNU__)
> 
> @@ -623,7 +632,8 @@ struct ext2_super_block {
>  	__u32	s_usr_quota_inum;	/* inode number of user quota file */
>  	__u32	s_grp_quota_inum;	/* inode number of group quota file */
>  	__u32	s_overhead_blocks;	/* overhead blocks/clusters in fs */
> -	__u32   s_reserved[109];        /* Padding to the end of the block */
> +	__u32	s_checksum;		/* crc32c(superblock) */
> +	__u32   s_reserved[108];        /* Padding to the end of the block */
>  };
> 
>  #define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)
> @@ -671,7 +681,9 @@ struct ext2_super_block {
>  #define EXT2_FEATURE_COMPAT_RESIZE_INODE	0x0010
>  #define EXT2_FEATURE_COMPAT_DIR_INDEX		0x0020
>  #define EXT2_FEATURE_COMPAT_LAZY_BG		0x0040
> -#define EXT2_FEATURE_COMPAT_EXCLUDE_INODE	0x0080
> +/* #define EXT2_FEATURE_COMPAT_EXCLUDE_INODE	0x0080 not used, legacy */
> +#define EXT2_FEATURE_COMPAT_EXCLUDE_BITMAP	0x0100
> +
> 
>  #define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER	0x0001
>  #define EXT2_FEATURE_RO_COMPAT_LARGE_FILE	0x0002
> @@ -683,6 +695,7 @@ struct ext2_super_block {
>  #define EXT4_FEATURE_RO_COMPAT_HAS_SNAPSHOT	0x0080
>  #define EXT4_FEATURE_RO_COMPAT_QUOTA		0x0100
>  #define EXT4_FEATURE_RO_COMPAT_BIGALLOC		0x0200
> +#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM	0x0400
> 
>  #define EXT2_FEATURE_INCOMPAT_COMPRESSION	0x0001
>  #define EXT2_FEATURE_INCOMPAT_FILETYPE		0x0002
> diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
> index 87b1a2e..d1c4a56 100644
> --- a/lib/ext2fs/swapfs.c
> +++ b/lib/ext2fs/swapfs.c
> @@ -78,6 +78,8 @@ void ext2fs_swap_super(struct ext2_super_block * sb)
>  	sb->s_snapshot_list = ext2fs_swab32(sb->s_snapshot_list);
>  	sb->s_usr_quota_inum = ext2fs_swab32(sb->s_usr_quota_inum);
>  	sb->s_grp_quota_inum = ext2fs_swab32(sb->s_grp_quota_inum);
> +	sb->s_overhead_blocks = ext2fs_swab32(sb->s_overhead_blocks);
> +	sb->s_checksum = ext2fs_swab32(sb->s_checksum);
> 
>  	for (i=0; i < 4; i++)
>  		sb->s_hash_seed[i] = ext2fs_swab32(sb->s_hash_seed[i]);
> @@ -106,6 +108,11 @@ void ext2fs_swap_group_desc2(ext2_filsys fs, struct ext2_group_desc *gdp)
>  	gdp->bg_free_inodes_count = ext2fs_swab16(gdp->bg_free_inodes_count);
>  	gdp->bg_used_dirs_count = ext2fs_swab16(gdp->bg_used_dirs_count);
>  	gdp->bg_flags = ext2fs_swab16(gdp->bg_flags);
> +	gdp->bg_exclude_bitmap_lo = ext2fs_swab32(gdp->bg_exclude_bitmap_lo);
> +	gdp->bg_block_bitmap_csum_lo =
> +		ext2fs_swab16(gdp->bg_block_bitmap_csum_lo);
> +	gdp->bg_inode_bitmap_csum_lo =
> +		ext2fs_swab16(gdp->bg_inode_bitmap_csum_lo);
>  	gdp->bg_itable_unused = ext2fs_swab16(gdp->bg_itable_unused);
>  	gdp->bg_checksum = ext2fs_swab16(gdp->bg_checksum);
>  	/* If we're 32-bit, we're done */
> @@ -125,6 +132,11 @@ void ext2fs_swap_group_desc2(ext2_filsys fs, struct ext2_group_desc *gdp)
>  	gdp4->bg_used_dirs_count_hi =
>  		ext2fs_swab16(gdp4->bg_used_dirs_count_hi);
>  	gdp4->bg_itable_unused_hi = ext2fs_swab16(gdp4->bg_itable_unused_hi);
> +	gdp->bg_exclude_bitmap_hi = ext2fs_swab16(gdp->bg_exclude_bitmap_hi);
> +	gdp->bg_block_bitmap_csum_hi =
> +		ext2fs_swab16(gdp->bg_block_bitmap_csum_hi);
> +	gdp->bg_inode_bitmap_csum_hi =
> +		ext2fs_swab16(gdp->bg_inode_bitmap_csum_hi);
>  }
> 
>  void ext2fs_swap_group_desc(struct ext2_group_desc *gdp)
> @@ -244,8 +256,8 @@ void ext2fs_swap_inode_full(ext2_filsys fs, struct ext2_inode_large *t,
>  		  ext2fs_swab16 (f->osd2.linux2.l_i_uid_high);
>  		t->osd2.linux2.l_i_gid_high =
>  		  ext2fs_swab16 (f->osd2.linux2.l_i_gid_high);
> -		t->osd2.linux2.l_i_reserved2 =
> -			ext2fs_swab32(f->osd2.linux2.l_i_reserved2);
> +		t->osd2.linux2.l_i_checksum =
> +			ext2fs_swab32(f->osd2.linux2.checksum);
>  		break;
>  	case EXT2_OS_HURD:
>  		t->osd1.hurd1.h_i_translator =
> diff --git a/lib/ext2fs/tst_inode_size.c b/lib/ext2fs/tst_inode_size.c
> index 962f1cd..a4f6247 100644
> --- a/lib/ext2fs/tst_inode_size.c
> +++ b/lib/ext2fs/tst_inode_size.c
> @@ -61,7 +61,8 @@ void check_structure_fields()
>  	check_field(osd2.linux2.l_i_file_acl_high);
>  	check_field(osd2.linux2.l_i_uid_high);
>  	check_field(osd2.linux2.l_i_gid_high);
> -	check_field(osd2.linux2.l_i_reserved2);
> +	check_field(osd2.linux2.l_i_checksum_lo);
> +	check_field(osd2.linux2.l_i_reserved);
>  	printf("Ending offset is %d\n\n", cur_offset);
>  #endif
>  }
> diff --git a/lib/ext2fs/tst_super_size.c b/lib/ext2fs/tst_super_size.c
> index 1e5a524..75659ae 100644
> --- a/lib/ext2fs/tst_super_size.c
> +++ b/lib/ext2fs/tst_super_size.c
> @@ -126,6 +126,7 @@ void check_superblock_fields()
>  	check_field(s_usr_quota_inum);
>  	check_field(s_grp_quota_inum);
>  	check_field(s_overhead_blocks);
> +	check_field(s_checksum);
>  	check_field(s_reserved);
>  	printf("Ending offset is %d\n\n", cur_offset);
>  #endif
> -- 
> 1.7.4.1.22.gec8e1.dirty
> 
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