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ext4: calculate and verify block bitmap checksum

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Compute and verify the checksum of the block bitmap; this checksum is
stored in the block group descriptor.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Darrick J. Wong
2012-04-29 18:35:10 -04:00
committed by Theodore Ts'o
parent 41a246d1ff
commit fa77dcfafe
6 changed files with 104 additions and 8 deletions
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44
fs/ext4/bitmap.c
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@@ -68,3 +68,47 @@ void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END)
gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
}
int ext4_block_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
struct ext4_group_desc *gdp,
struct buffer_head *bh, int sz)
{
__u32 hi;
__u32 provided, calculated;
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return 1;
provided = le16_to_cpu(gdp->bg_block_bitmap_csum_lo);
calculated = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END) {
hi = le16_to_cpu(gdp->bg_block_bitmap_csum_hi);
provided |= (hi << 16);
} else
calculated &= 0xFFFF;
if (provided == calculated)
return 1;
ext4_error(sb, "Bad block bitmap checksum: block_group = %u", group);
return 0;
}
void ext4_block_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
struct ext4_group_desc *gdp,
struct buffer_head *bh, int sz)
{
__u32 csum;
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
gdp->bg_block_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END)
gdp->bg_block_bitmap_csum_hi = cpu_to_le16(csum >> 16);
}