ext4: calculate and verify block bitmap checksum
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>
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 4bbd07a..0a64e4d 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -174,6 +174,8 @@
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);
@@ -210,6 +212,9 @@
*/
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
@@ -276,9 +281,9 @@
}
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;
@@ -325,6 +330,23 @@
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
@@ -355,12 +377,12 @@
}
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)) {
@@ -379,7 +401,7 @@
*/
set_bitmap_uptodate(bh);
unlock_buffer(bh);
- return bh;
+ goto verify;
}
/*
* submit the buffer_head for reading
@@ -390,6 +412,9 @@
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 */
@@ -412,7 +437,7 @@
}
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;
}