Re: More ext4 acl/xattr corruption - 4th occurence now

[Manish Katiyar <mkatiyar@gmail.com>]

On Thu, May 14, 2009 at 4:37 PM, Kevin Shanahan <kmshanah@ucwb.org.au> wrote:
> On Thu, May 14, 2009 at 12:40:11AM -0400, Theodore Tso wrote:
>> On Wed, May 13, 2009 at 03:56:34PM +0930, Kevin Shanahan wrote:
>> >
>> > Now, this is (possibly) interesting - that block contains a bunch of
>> > file data. Looks like a html email (I can tell it's email because of
>> > the FIXED_ prefix added to the tags by the mail sanitizer).
>>
>> That is interesting.  Knowing that it is file data means we might be
>> able to track things down this way.
>>
>> Are you able to apply the following patch to your kernel?

Hi Ted,

If we have the possibility of applying patches why not apply this too
and try http://markmail.org/message/e3uwzxrd42isxczg . After all it
originated from this bug only.

Thanks -
Manish


>> 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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-- 
Thanks -
Manish
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