linux-kernel - Re: [PATCH v2 4/4] ocfs2: check/fix inode block for online file check

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Message-ID: <5638707A.8000007@oracle.com>
Date:	Tue, 03 Nov 2015 16:29:46 +0800
From:	Junxiao Bi <junxiao.bi@...cle.com>
To:	Gang He <ghe@...e.com>, Mark Fasheh <MFasheh@...e.com>,
	rgoldwyn@...e.de
CC:	akpm@...ux-foundation.org, ocfs2-devel@....oracle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] ocfs2: check/fix inode block for online file check

On 11/03/2015 04:15 PM, Gang He wrote:
> Hello Junxiao,
> 
> See my comments inline.
> 
> 
>>>>
>> Hi Gang,
>>
>> This is not like a right patch.
>> First, online file check only checks inode's block number, valid flag,
>> fs generation value, and meta ecc. I never see a real corruption
>> happened only on this field, if these fields are corrupted, that means
>> something bad may happen on other place. So fix this field may not help
>> and even cause corruption more hard.
> This online file check/fix feature is used to check/fix some light file meta block corruption, instead of turning a file system off and using fsck.ocfs2.
What's light meta block corruption? Do you have a case about it?
> e.g. meta ecc error, we really need not to use fsck.ocfs2. 
> of course, this feature does not replace fsck.ocfs2 and touch some complicated meta block problems, if there is some potential problem in some areas, we can discuss them one by one.
> 
> 
> 
>> Second, the repair way is wrong. In
>> ocfs2_filecheck_repair_inode_block(), if these fields in disk don't
>> match the ones in memory, the ones in memory are used to update the disk
>> fields. The question is how do you know these field in memory are
>> right(they may be the real corrupted ones)?
> Here, if the inode block was corrupted, the file system is not able to load it into the memory.
How do you know inode block corrupted? If bh for inode block is
overwritten, i mean bh corrupted, the repair will corrupted a good inode
block.

Thanks,
Junxiao.

> ocfs2_filecheck_repair_inode_block() will able to load it into the memory, since it try to fix these light-level problem before loading.
> if the fix is OK, the changed meta-block can pass the block-validate function and load into the memory as a inode object.
> Since the file system is under a cluster environment, we have to use some existing function and code path to keep these block operation under a cluster lock.
> 
> 
> Thanks
> Gang
> 
>>
>> Thanks,
>> Junxiao.
>> On 10/28/2015 02:26 PM, Gang He wrote:
>>> +static int ocfs2_filecheck_repair_inode_block(struct super_block *sb,
>>> +			       struct buffer_head *bh)
>>> +{
>>> +	int rc;
>>> +	int changed = 0;
>>> +	struct ocfs2_dinode *di = (struct ocfs2_dinode *)bh->b_data;
>>> +
>>> +	rc = ocfs2_filecheck_validate_inode_block(sb, bh);
>>> +	/* Can't fix invalid inode block */
>>> +	if (!rc || rc == -OCFS2_FILECHECK_ERR_INVALIDINO)
>>> +		return rc;
>>> +
>>> +	trace_ocfs2_filecheck_repair_inode_block(
>>> +		(unsigned long long)bh->b_blocknr);
>>> +
>>> +	if (ocfs2_is_hard_readonly(OCFS2_SB(sb)) ||
>>> +		ocfs2_is_soft_readonly(OCFS2_SB(sb))) {
>>> +		mlog(ML_ERROR,
>>> +			"Filecheck: try to repair dinode #%llu on readonly filesystem\n",
>>> +			(unsigned long long)bh->b_blocknr);
>>> +		return -OCFS2_FILECHECK_ERR_READONLY;
>>> +	}
>>> +
>>> +	if (le64_to_cpu(di->i_blkno) != bh->b_blocknr) {
>>> +		di->i_blkno = cpu_to_le64(bh->b_blocknr);
>>> +		changed = 1;
>>> +		mlog(ML_ERROR,
>>> +			"Filecheck: reset dinode #%llu: i_blkno to %llu\n",
>>> +			(unsigned long long)bh->b_blocknr,
>>> +			(unsigned long long)le64_to_cpu(di->i_blkno));
>>> +	}
>>> +
>>> +	if (!(di->i_flags & cpu_to_le32(OCFS2_VALID_FL))) {
>>> +		di->i_flags |= cpu_to_le32(OCFS2_VALID_FL);
>>> +		changed = 1;
>>> +		mlog(ML_ERROR,
>>> +			"Filecheck: reset dinode #%llu: OCFS2_VALID_FL is set\n",
>>> +			(unsigned long long)bh->b_blocknr);
>>> +	}
>>> +
>>> +	if (le32_to_cpu(di->i_fs_generation) !=
>>> +	    OCFS2_SB(sb)->fs_generation) {
>>> +		di->i_fs_generation = cpu_to_le32(OCFS2_SB(sb)->fs_generation);
>>> +		changed = 1;
>>> +		mlog(ML_ERROR,
>>> +			"Filecheck: reset dinode #%llu: fs_generation to %u\n",
>>> +			(unsigned long long)bh->b_blocknr,
>>> +			le32_to_cpu(di->i_fs_generation));
>>> +	}
>>> +
>>> +	if (changed ||
>>> +		ocfs2_validate_meta_ecc(sb, bh->b_data, &di->i_check)) {
>>> +		ocfs2_compute_meta_ecc(sb, bh->b_data, &di->i_check);
>>> +		mark_buffer_dirty(bh);
>>> +		mlog(ML_ERROR,
>>> +			"Filecheck: reset dinode #%llu: compute meta ecc\n",
>>> +			(unsigned long long)bh->b_blocknr);
>>> +	}
>>> +
>>> +	return 0;
>>> +}
> 

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