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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>
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Darrick J. Wong authored and Theodore Ts'o committed Apr 29, 2012
1 parent 41a246d commit fa77dcf
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Showing 6 changed files with 104 additions and 8 deletions.
39 changes: 32 additions & 7 deletions fs/ext4/balloc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -174,6 +174,8 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
ext4_free_inodes_set(sb, gdp, 0);
ext4_itable_unused_set(sb, gdp, 0);
memset(bh->b_data, 0xff, sb->s_blocksize);
ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
return;
}
memset(bh->b_data, 0, sb->s_blocksize);
Expand Down Expand Up @@ -210,6 +212,9 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
*/
ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
sb->s_blocksize * 8, bh->b_data);
ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
}

/* Return the number of free blocks in a block group. It is used when
Expand Down Expand Up @@ -276,9 +281,9 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
}

static int ext4_valid_block_bitmap(struct super_block *sb,
struct ext4_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
struct ext4_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
{
ext4_grpblk_t offset;
ext4_grpblk_t next_zero_bit;
Expand Down Expand Up @@ -325,6 +330,23 @@ static int ext4_valid_block_bitmap(struct super_block *sb,
block_group, bitmap_blk);
return 0;
}

void ext4_validate_block_bitmap(struct super_block *sb,
struct ext4_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
{
if (buffer_verified(bh))
return;

ext4_lock_group(sb, block_group);
if (ext4_valid_block_bitmap(sb, desc, block_group, bh) &&
ext4_block_bitmap_csum_verify(sb, block_group, desc, bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8))
set_buffer_verified(bh);
ext4_unlock_group(sb, block_group);
}

/**
* ext4_read_block_bitmap()
* @sb: super block
Expand Down Expand Up @@ -355,12 +377,12 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
}

if (bitmap_uptodate(bh))
return bh;
goto verify;

lock_buffer(bh);
if (bitmap_uptodate(bh)) {
unlock_buffer(bh);
return bh;
goto verify;
}
ext4_lock_group(sb, block_group);
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
Expand All @@ -379,7 +401,7 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
*/
set_bitmap_uptodate(bh);
unlock_buffer(bh);
return bh;
goto verify;
}
/*
* submit the buffer_head for reading
Expand All @@ -390,6 +412,9 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
get_bh(bh);
submit_bh(READ, bh);
return bh;
verify:
ext4_validate_block_bitmap(sb, desc, block_group, bh);
return bh;
}

/* Returns 0 on success, 1 on error */
Expand All @@ -412,7 +437,7 @@ int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
}
clear_buffer_new(bh);
/* Panic or remount fs read-only if block bitmap is invalid */
ext4_valid_block_bitmap(sb, desc, block_group, bh);
ext4_validate_block_bitmap(sb, desc, block_group, bh);
return 0;
}

Expand Down
44 changes: 44 additions & 0 deletions fs/ext4/bitmap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}
10 changes: 10 additions & 0 deletions fs/ext4/ext4.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1857,8 +1857,18 @@ void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
struct ext4_group_desc *gdp,
struct buffer_head *bh, int sz);
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);
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);

/* balloc.c */
extern void ext4_validate_block_bitmap(struct super_block *sb,
struct ext4_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh);
extern unsigned int ext4_block_group(struct super_block *sb,
ext4_fsblk_t blocknr);
extern ext4_grpblk_t ext4_block_group_offset(struct super_block *sb,
Expand Down
4 changes: 4 additions & 0 deletions fs/ext4/ialloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -753,6 +753,10 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
ext4_free_group_clusters_set(sb, gdp,
ext4_free_clusters_after_init(sb, group, gdp));
ext4_block_bitmap_csum_set(sb, group, gdp,
block_bitmap_bh,
EXT4_BLOCKS_PER_GROUP(sb) /
8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, group,
gdp);
}
Expand Down
8 changes: 7 additions & 1 deletion fs/ext4/mballoc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -788,7 +788,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
int first_block;
struct super_block *sb;
struct buffer_head *bhs;
struct buffer_head **bh;
struct buffer_head **bh = NULL;
struct inode *inode;
char *data;
char *bitmap;
Expand Down Expand Up @@ -2797,6 +2797,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
}
len = ext4_free_group_clusters(sb, gdp) - ac->ac_b_ex.fe_len;
ext4_free_group_clusters_set(sb, gdp, len);
ext4_block_bitmap_csum_set(sb, ac->ac_b_ex.fe_group, gdp, bitmap_bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, ac->ac_b_ex.fe_group, gdp);

ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
Expand Down Expand Up @@ -4659,6 +4661,8 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,

ret = ext4_free_group_clusters(sb, gdp) + count_clusters;
ext4_free_group_clusters_set(sb, gdp, ret);
ext4_block_bitmap_csum_set(sb, block_group, gdp, bitmap_bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
ext4_unlock_group(sb, block_group);
percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);
Expand Down Expand Up @@ -4803,6 +4807,8 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
mb_free_blocks(NULL, &e4b, bit, count);
blk_free_count = blocks_freed + ext4_free_group_clusters(sb, desc);
ext4_free_group_clusters_set(sb, desc, blk_free_count);
ext4_block_bitmap_csum_set(sb, block_group, desc, bitmap_bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
ext4_unlock_group(sb, block_group);
percpu_counter_add(&sbi->s_freeclusters_counter,
Expand Down
7 changes: 7 additions & 0 deletions fs/ext4/resize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1107,6 +1107,13 @@ static int ext4_set_bitmap_checksums(struct super_block *sb,
EXT4_INODES_PER_GROUP(sb) / 8);
brelse(bh);

bh = ext4_get_bitmap(sb, group_data->block_bitmap);
if (!bh)
return -EIO;
ext4_block_bitmap_csum_set(sb, group, gdp, bh,
EXT4_BLOCKS_PER_GROUP(sb) / 8);
brelse(bh);

return 0;
}

Expand Down

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