Re: [vserver] problem accessing NetApp Filer snapshot

Herbert Poetzl wrote:
> On Thu, Sep 06, 2007 at 06:11:27PM -0700, Dallas Kashuba wrote:
>> We have several vserver guests NFS mounting volumes being served from
>> Network Appliance filers. The NFS mounting works as expected, other
>> than access to the snapshots provided by the NetApp filesystem.
>
> NFS tasgging is disabled, I presume?
>
>> Under normal circumstances (non-vserver), you access the snapshot
>> from anywhere along the filesystem by simply doing 'cd .snapshot'.
>> Within there you will see a directory for each snapshot named
>> something like hourly.0, nightly.0, or weekly.1 (etc), which contain
>> copies of the files from those points in time. They work like any
>> other directory aside from being read-only and being hidden from 'ls'
>> output. Any user can access the snapshots for any part of the
>> filesystem that user ordinarily has access to. No root access is
>> required.
>>
>> Inside the vserver guests it does not work as expected, though.
>> Attempting to 'cd .snapshot' never works at all unless BINARY_MOUNT
>> is added to ccapabilities. This seems odd to me as there is no
>> mounting taking place from what I understand, but the kernel seems to
>> think there is.
>
> there is a mount happening in this case,
> because the filer provides the snapshot
> as a different (subtree) export
> (but it happens inside the kernel)
>
>> With BINARY_MOUNT added, the root user is then able to access
>> .snapshot in all cases. non-root users cannot, though. A non-root user
>> CAN access a .snapshot portion of the filesystem after the root user
>> has accessed it once previously, though. Here's an example...
>
> and this works fine on the host system?
> (I mean as non-root user on the host?)
>
>> vserver03:/etc/vservers/patrick# vserver patrick enter
>> patrick:/# su - testuser
>> [patrick]$ whoami
>> testuser
>> [patrick]$ cd .snapshot
>> -su: cd: .snapshot: Operation not permitted
>> # (Note the "Operation not permitted" error)
>>
>> [patrick]$ logout
>> # (back to root now)
>>
>> patrick:/# cd /home/testuser/.snapshot
>> patrick:/# su - testuser
>> [patrick]$ cd .snapshot
>> # (after accessing it once as root, it's now accessible as the non-
>> root user)
>>
>> [patrick]$ ls
>> hourly.0 hourly.1 nightly.0 nightly.1 weekly.0 weekly.1
>> [patrick]$ ls hourly.0
>> ls: hourly.0: Operation not permitted
>> # (access one more level down the filesystem is still not permitted)
>>
>> [patrick]$ logout
>> patrick:/# cd /home/testuser/.snapshot/
>> patrick:/home/testuser/.snapshot# ls -l
>> total 32
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 hourly.0
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 hourly.1
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 nightly.0
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 nightly.1
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 weekly.0
>> drwxr-x--x 7 testuser users 4096 Jul 3 10:53 weekly.1
>>
>> # (doing an ls -la as root accesses every directory below)
>>
>> patrick:/home/testuser/.snapshot# su - testuser
>> [patrick]$ cd .snapshot/hourly.0
>> [patrick]$ ls
>> Maildir logs testdomain.com svn svntest
>> [patrick]$ cd ../weekly.1
>> [patrick]$ ls
>> Maildir logs testdomain.com svn svntest
>> [patrick]$ logout
>>
>> After the root user ran 'ls -la' inside .snapshot, the non-root user
>> could then access all of the hourly.0, weekly.1 etc snapshot
>> directories below.
>
> this is most likely because the entries are
> already in the dentry cache on the 'client'
>
>> Does anyone have any clues about how to fix this?
>
>> Ideally BINARY_MOUNT would not be needed at all, but
>
> well, let's postpone this question ...
>
>> it's ok as long as it works normally for non-root users.
>>
>> Any ideas are appreciated!
>
> yeah, please provide the following debug info:
>
> - complete rpc and nfs(d) debug output for all
> cases, i.e. root/user on host/guest
> - Linux-VServer debug dmesg output
>
> we know that the subtree checks (depending on
> the nfs version) cause some issues, and I think
> we can fix them with sufficient data ...

Didn't we come to the conclusion that this problem was due to the extra
vx_capable in vfs_kern_mount when this was discussed on IRC, which ought
to be just vx_ccaps?

> TIA,
> Herbert
>
>> Thanks!
>> Dallas

-- 
Daniel Hokka Zakrisson