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

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Date:   Tue, 23 May 2017 08:50:49 +0900
From:   Hyunchul Lee <hyc.lee@...il.com>
To:     Richard Weinberger <richard@....at>
Cc:     david@...ma-star.at, bfields@...hat.com, dedekind1@...il.com,
        rockdotlee@...il.com, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, kernel-team@....com,
        linux-mtd@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        adilger.kernel@...ger.ca, akpm@...ux-foundation.org,
        marcus.folkesson@...il.com, leon.pollak@...il.com
Subject: Re: [PATCH 4/6] ubifs: Maintain a parent pointer

Hi Richard,

On Mon, May 22, 2017 at 10:45:08AM +0200, Richard Weinberger wrote:
> 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.

Is writing old_inode->i_ctime required? I guess that it is needed only when 
IS_SYNC(old_inode) is true, otherwise we don't need to guarantee that ctime
is synced.

> 
> Thanks,
> //richard
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

-- 

Thanks,
Hyunchul

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