>> If so,
>> hopefully we'll be able to catch whatever is causing the problem in
>> the act.
>
> Sure - now running with 2.6.29.3 + your patch.
>
> patching file fs/ext4/inode.c
> Hunk #1 succeeded at 1040 with fuzz 1 (offset -80 lines).
> Hunk #2 succeeded at 1113 (offset -81 lines).
> Hunk #3 succeeded at 1184 (offset -93 lines).
>
> I'll report any hits for "check_block_validity" in syslog.
>
> Thankyou, much appreciated.
>
> Cheers,
> Kevin.
>
>> commit 8ff799da106e9fc4da9b2a3753b5b86caab27f13
>> Author: Theodore Ts'o <tytso@mit.edu>
>> Date: Thu May 14 00:39:48 2009 -0400
>>
>> ext4: Add a block validity check to ext4_get_blocks_wrap()
>>
>> A few users with very large disks have been reporting low block number
>> filesystem corruptions, potentially zapping the block group
>> descriptors or inodes in the first inode table block. It's not clear
>> what is causing this, but most recently, it appears that whatever is
>> trashing the filesystem metadata appears to be file data. So let's
>> try to set a trap for the corruption in ext4_get_blocks_wrap(), which
>> is where logical blocks in an inode are mapped to physical blocks.
>>
>> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index 4e7f363..4fad4fa 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -1120,6 +1120,35 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
>> ext4_discard_preallocations(inode);
>> }
>>
>> +static int check_block_validity(struct inode *inode, sector_t logical,
>> + sector_t phys, int len)
>> +{
>> + ext4_fsblk_t valid_block, itable_block;
>> + struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
>> + struct ext4_group_desc *gdp = ext4_get_group_desc(inode->i_sb, 0, 0);
>> + unsigned int itable_len = EXT4_SB(inode->i_sb)->s_itb_per_group;
>> +
>> + valid_block = le32_to_cpu(es->s_first_data_block) +
>> + EXT4_SB(inode->i_sb)->s_gdb_count;
>> + itable_block = ext4_inode_table(inode->i_sb, gdp);
>> +
>> + if (unlikely((phys <= valid_block) ||
>> + ((phys + len - 1) > ext4_blocks_count(es)) ||
>> + ((phys >= itable_block) &&
>> + (phys <= itable_block + itable_len)) ||
>> + ((phys + len - 1 >= itable_block) &&
>> + (phys + len - 1 <= itable_block + itable_len)))) {
>> + ext4_error(inode->i_sb, "check_block_validity",
>> + "inode #%lu logical block %llu mapped to %llu "
>> + "(size %d)", inode->i_ino,
>> + (unsigned long long) logical,
>> + (unsigned long long) phys, len);
>> + WARN_ON(1);
>> + return -EIO;
>> + }
>> + return 0;
>> +}
>> +
>> /*
>> * The ext4_get_blocks_wrap() function try to look up the requested blocks,
>> * and returns if the blocks are already mapped.
>> @@ -1165,6 +1194,13 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
>> }
>> up_read((&EXT4_I(inode)->i_data_sem));
>>
>> + if (retval > 0 && buffer_mapped(bh)) {
>> + int ret = check_block_validity(inode, block,
>> + bh->b_blocknr, retval);
>> + if (ret != 0)
>> + return ret;
>> + }
>> +
>> /* If it is only a block(s) look up */
>> if (!create)
>> return retval;
>> @@ -1241,6 +1277,12 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
>> }
>>
>> up_write((&EXT4_I(inode)->i_data_sem));
>> + if (retval > 0 && buffer_mapped(bh)) {
>> + int ret = check_block_validity(inode, block,
>> + bh->b_blocknr, retval);
>> + if (ret != 0)
>> + return ret;
>> + }
>> return retval;
>> }
>>
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