linux-kernel - Re: [PATCH 4/6] ubifs: Maintain a parent pointer

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Date:   Mon, 22 May 2017 10:45:08 +0200
From:   Richard Weinberger <richard@....at>
To:     Hyunchul Lee <hyc.lee@...il.com>
Cc:     linux-mtd@...ts.infradead.org, david@...ma-star.at,
        bfields@...hat.com, dedekind1@...il.com,
        linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        leon.pollak@...il.com, adilger.kernel@...ger.ca,
        linux-fsdevel@...r.kernel.org, marcus.folkesson@...il.com,
        akpm@...ux-foundation.org, rockdotlee@...il.com,
        kernel-team@....com
Subject: Re: [PATCH 4/6] ubifs: Maintain a parent pointer

Hyunchul,

Am 22.05.2017 um 06:30 schrieb Hyunchul Lee:
>> +	if (move)
>> +		old_inode_ui->parent_inum = new_dir->i_ino;
>> +
>>  	err = ubifs_jnl_rename(c, old_dir, old_inode, &old_nm, new_dir,
>>  			       new_inode, &new_nm, whiteout, sync);
> 
> I think that old_inode_ui->parent_inum could point old_dir, even though old_inode
> is a child of new_dir. this could happen that there is power-cut before
> old_inode is synced. so I guess that old_inode is needed to be written with
> rename's node group in ubifs_jnl_rename. is it right?

I assumed that the journal does this already because we change old_inode->i_ctime
in this function too.
But checking the code showed the opposite.
So, if we face a power-cut the rename can succeed but we lose the ctime change.

This needs to be addressed before we can add the parent pointer.

Thanks,
//richard