linux-kernel - Re: [f2fs-dev] [PATCH v3] f2fs: change the current atomic write way

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Message-ID: <227d10d5-2afe-acfa-7cfc-3a2f45331c6f@kernel.org>
Date:   Tue, 24 May 2022 14:29:49 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Daeho Jeong <daeho43@...il.com>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: change the current atomic write way

On 2022/5/24 2:03, Jaegeuk Kim wrote:
> On 05/22, Chao Yu wrote:
>> On 2022/4/29 2:18, Daeho Jeong wrote:> +		*old_addr = dn.data_blkaddr;
>>> +		f2fs_truncate_data_blocks_range(&dn, 1);
>>> +		dec_valid_block_count(sbi, F2FS_I(inode)->cow_inode, count);
>>> +		inc_valid_block_count(sbi, inode, &count);
>>> +		f2fs_replace_block(sbi, &dn, dn.data_blkaddr, new_addr,
>>> +					ni.version, true, false);
>>
>> My concern is, if cow_inode's data was persisted into previous checkpoint,
>> and then f2fs_replace_block() will update SSA from cow_inode to inode?
> 
> SSA for original file is intact, so we'll see the orignal file's block addresses
> and SSA, if we flush cow_inode's SSA after committing the atomic writes?
> It'd be good to flush any SSA for cow_inode, since we'll truncate
> cow_inode after powercut by the ohphan recovery?

I think it's safe for recovery flow, but before that, fsck will report inconsistent
status during checking orphan atomic_write inode.

Thanks,

> 
>> it will cause inconsistent status of last valid checkpoint? Or am I mssing
>> something?
>>
>>> -		f2fs_submit_merged_write_cond(sbi, inode, NULL, 0, DATA);
>>> +			new = f2fs_kmem_cache_alloc(revoke_entry_slab, GFP_NOFS,
>>> +							true, NULL);
>>> +			if (!new) {
>>> +				f2fs_put_dnode(&dn);
>>> +				ret = -ENOMEM;
>>> +				goto out;
>>
>> It doesn't need to handle failure of f2fs_kmem_cache_alloc()
>> due to nofail parameter is true.
>>
>> Thanks,
>>
>>
>> _______________________________________________
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>> Linux-f2fs-devel@...ts.sourceforge.net
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