linux-kernel - Re: [PATCH v2 2/2] ceph: quota: fix quota subdir mounts

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Date:   Mon, 18 Mar 2019 10:55:45 +0000
From:   Luis Henriques <lhenriques@...e.com>
To:     "Yan\, Zheng" <ukernel@...il.com>
Cc:     Gregory Farnum <gfarnum@...hat.com>,
        "Yan\, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hendrik Peyerl <hpeyerl@...sline.net>
Subject: Re: [PATCH v2 2/2] ceph: quota: fix quota subdir mounts

"Yan, Zheng" <ukernel@...il.com> writes:

> On Mon, Mar 18, 2019 at 5:06 PM Gregory Farnum <gfarnum@...hat.com> wrote:
>>
>> On Mon, Mar 18, 2019 at 2:32 PM Yan, Zheng <ukernel@...il.com> wrote:
>> > After reading the code carefully. I feel a little uncomfortable with
>> > the "lookup_ino" in get_quota_realm.  how about populating directories
>> > above the 'mount subdir' during mounting (similar to cifs_get_root ).

Wouldn't it be a problem if the directory layout (or, in this case, the
snaprealm layout) change during the mount lifetime?  In that case we
would need to do this lookup anyway.

>>
>> Isn't that going to be a problem for any clients which have
>>restricted filesystem access permissions? They may not be able to see
>>all the directories above their mount point.  -Greg
>
> using lookup_ino to get inode above the "mount subdir" has the same problem
>

In this case I believe we get an -EPERM from the MDS.  And then the
client simply falls back to the 'default' behaviour, which is to allow
the user to create/write to files as if there were no quotas set.

Cheers,
-- 
Luis