linux-ext4 - Re: [PATCH 4/6] ubifs: Maintain a parent pointer

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Message-ID: <99b3f295-be4e-14a1-a21d-e9055949a8ef@nod.at>
Date:   Tue, 23 May 2017 10:42:31 +0200
From:   Richard Weinberger <richard@....at>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-mtd@...ts.infradead.org, david@...ma-star.at,
        dedekind1@...il.com, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        adilger.kernel@...ger.ca, akpm@...ux-foundation.org,
        linux-ext4@...r.kernel.org, bfields@...hat.com,
        marcus.folkesson@...il.com, hyc.lee@...il.com,
        rockdotlee@...il.com, leon.pollak@...il.com
Subject: Re: [PATCH 4/6] ubifs: Maintain a parent pointer

Christoph,

Am 23.05.2017 um 10:37 schrieb Christoph Hellwig:
> On Sun, May 21, 2017 at 10:20:49PM +0200, Richard Weinberger wrote:
>> The new feature UBIFS_FLG_PARENTPOINTER allows looking
>> up the parent. Usually the Linux VFS walks down the filesystem
>> and no parent pointers are needed. But when a filesystem
>> is exportable via NFS such a lookup is needed.
>> We can use a padding field in struct ubifs_ino_node to
>> maintain a pointer to the parent inode.
> 
> Note that nfsd/exportfs will only do this for directories, and beacause
> we hardlinks for other objects that is an important distinction.
> 
> I think the ubifs code should make sure to only maintain the parent
> pointers for directories, otherwise confusion and abuses will happen.

Thanks for the info, I'll massage the code in that direction.

Thanks,
//richard