linux-kernel - Re: [RFC PATCH v2 0/3] ceph: add support for snapshot names encryption

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Message-ID: <40c9ebed-2c49-3a91-7893-5d0c7f124ead@redhat.com>
Date:   Thu, 17 Mar 2022 19:28:45 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Luís Henriques <lhenriques@...e.de>
Cc:     Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 0/3] ceph: add support for snapshot names
 encryption


On 3/17/22 7:11 PM, Luís Henriques wrote:
> Xiubo Li <xiubli@...hat.com> writes:
>
>> On 3/17/22 6:01 PM, Jeff Layton wrote:
>>> I'm not sure we want to worry about .snap directories here since they
>>> aren't "real". IIRC, snaps are inherited from parents too, so you could
>>> do something like
>>>
>>>       mkdir dir1
>>>       mkdir dir1/.snap/snap1
>>>       mkdir dir1/dir2
>>>       fscrypt encrypt dir1/dir2
>>>
>>> There should be nothing to prevent encrypting dir2, but I'm pretty sure
>>> dir2/.snap will not be empty at that point.
>> If we don't take care of this. Then we don't know which snapshots should do
>> encrypt/dencrypt and which shouldn't when building the path in lookup and when
>> reading the snapdir ?
> In my patchset (which I plan to send a new revision later today, I think I
> still need to rebase it) this is handled by using the *real* snapshot
> parent inode.  If we're decrypting/encrypting a name for a snapshot that
> starts with a '_' character, we first find the parent inode for that
> snapshot and only do the operation if that parent is encrypted.

Yeah, this is correct. And in my previous patches it worked well.


>
> In the other email I suggested that we could prevent enabling encryption
> in a directory when there are snapshots above in the hierarchy.

I think this is incorrect. Or once there has a snapshot in the root 
directory, then you couldn't enable encryption any more in any subdirs ...


>   But now
> that I think more about it, it won't solve any problem because you could
> create those snapshots later and then you would still need to handle these
> (non-encrypted) "_name_xxxx" snapshots anyway.

You only need to take care of the *real* or local snapshots.

-- Xiubo

>
> Cheers,