[Lustre-devel] Re-direction inodes

[Lustre-devel] Re-direction inodes

[Peter Braam]

Hi Nikita -

I have a need in doing an architecture for a customer of a Lustre client
feature to have different data/page caches associated with an inode,
depending on the user that accesses it.    So when a file is read, user A
will read different data from user B (assume the same for writes, but I
think this is a read-only feature).

I remember that in the Coda file system we could easily re-direct I/O to
another inode using almost standard features in the VFS/page caches.  Is
this still the case?  Would this work for the purpose I describe above?

Thanks.

Peter
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[Lustre-devel] Re-direction inodes

[Nikita Danilov]

Peter Braam writes:
 > Hi Nikita -
 > 
 > I have a need in doing an architecture for a customer of a Lustre client
 > feature to have different data/page caches associated with an inode,
 > depending on the user that accesses it.    So when a file is read, user A
 > will read different data from user B (assume the same for writes, but I
 > think this is a read-only feature).
 > 
 > I remember that in the Coda file system we could easily re-direct I/O to
 > another inode using almost standard features in the VFS/page caches.  Is
 > this still the case?  Would this work for the purpose I describe above?

I am not sure how this can be done with the VFS mechanisms. Alex pointed
out that some kind of stacked file system similar to smfs can be used
for this purpose.

 > 
 > Thanks.
 > 
 > Peter

Nikita.

[Lustre-devel] Re-direction inodes

[Peter Braam]

On 6/2/08 8:11 PM, "Nikita Danilov" <Nikita.Danilov@Sun.COM> wrote:

> Peter Braam writes:
>> Hi Nikita -
>> 
>> I have a need in doing an architecture for a customer of a Lustre client
>> feature to have different data/page caches associated with an inode,
>> depending on the user that accesses it.    So when a file is read, user A
>> will read different data from user B (assume the same for writes, but I
>> think this is a read-only feature).
>> 
>> I remember that in the Coda file system we could easily re-direct I/O to
>> another inode using almost standard features in the VFS/page caches.  Is
>> this still the case?  Would this work for the purpose I describe above?
> 
> I am not sure how this can be done with the VFS mechanisms. Alex pointed
> out that some kind of stacked file system similar to smfs can be used
> for this purpose.

Thanks for replying so quickly. After I read your reply I began to realize
that what Coda does is too static to solve this problem.

I'm going to schedule some phone time with you to discuss this further -
because the customer I am talking to needs something and there are two
approaches, one is smfs the other is to re-do the pre-processing of the
files on the client when there are multiple different user views (neither is
all that nice).

Peter
> 
>> 
>> Thanks.
>> 
>> Peter
> 
> Nikita.

[Lustre-devel] Re-direction inodes

[Andreas Dilger]

On Jun 02, 2008  08:59 +0900, Peter J. Braam wrote:
> I have a need in doing an architecture for a customer of a Lustre client
> feature to have different data/page caches associated with an inode,
> depending on the user that accesses it.    So when a file is read, user A
> will read different data from user B (assume the same for writes, but I
> think this is a read-only feature).

Initially when I read this, I thought you were only trying to keep the
client-side cache separate, which could be done by adding the UID into
the inode lookup function for ll_test_inode() and treating these files
separately in the client-side cache.  That would be useful to avoid e.g.
user A reading "securefile" into memory, and user B being able to access
it from cache due to client-local access permissions allowing it.

> I remember that in the Coda file system we could easily re-direct I/O to
> another inode using almost standard features in the VFS/page caches.  Is
> this still the case?  Would this work for the purpose I describe above?

On later reading, it seems you want to have completely independent
file contents for each user, but they share the same pathname.  In some
filesystems it is possible to encode part of the pathname somewhat like:

	/home///$UID///file

but I think you are proposing a completely transparent mapping of content:

alice> cat /etc/passwd
alice:x:1000:1000:Alice:/home/alice:/bin/bash

bob> cat /etc/passwd
bob:x:1001:1001:Bob:/home/bob:/bin/bash

correct?

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

[Lustre-devel] Re-direction inodes

[Peter Braam]

The last sentence in your message is correct.  But it seems that Nikita and
I have managed to design it "out of the way" - I'll write it up and share it
with you.

Peter


On 6/3/08 2:09 AM, "Andreas Dilger" <adilger@sun.com> wrote:

> On Jun 02, 2008  08:59 +0900, Peter J. Braam wrote:
>> I have a need in doing an architecture for a customer of a Lustre client
>> feature to have different data/page caches associated with an inode,
>> depending on the user that accesses it.    So when a file is read, user A
>> will read different data from user B (assume the same for writes, but I
>> think this is a read-only feature).
> 
> Initially when I read this, I thought you were only trying to keep the
> client-side cache separate, which could be done by adding the UID into
> the inode lookup function for ll_test_inode() and treating these files
> separately in the client-side cache.  That would be useful to avoid e.g.
> user A reading "securefile" into memory, and user B being able to access
> it from cache due to client-local access permissions allowing it.
> 
>> I remember that in the Coda file system we could easily re-direct I/O to
>> another inode using almost standard features in the VFS/page caches.  Is
>> this still the case?  Would this work for the purpose I describe above?
> 
> On later reading, it seems you want to have completely independent
> file contents for each user, but they share the same pathname.  In some
> filesystems it is possible to encode part of the pathname somewhat like:
> 
> /home///$UID///file
> 
> but I think you are proposing a completely transparent mapping of content:
> 
> alice> cat /etc/passwd
> alice:x:1000:1000:Alice:/home/alice:/bin/bash
> 
> bob> cat /etc/passwd
> bob:x:1001:1001:Bob:/home/bob:/bin/bash
> 
> correct?
> 
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
> 
> _______________________________________________
> Lustre-devel mailing list
> Lustre-devel at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-devel

[Lustre-devel] Re-direction inodes

[Daire Byrne]

----- "Andreas Dilger" <adilger@sun.com> wrote:

> filesystems it is possible to encode part of the pathname somewhat
> like:
> 
> 	/home///$UID///file
> 
> but I think you are proposing a completely transparent mapping of
> content:
> 
> alice> cat /etc/passwd
> alice:x:1000:1000:Alice:/home/alice:/bin/bash
> 
> bob> cat /etc/passwd
> bob:x:1001:1001:Bob:/home/bob:/bin/bash

I *think* autofs5 allows for $UID/$GID in mount maps to provide different mountpoints - but that only gives you a whole unique tree not individual files. Depending on the number of files you wish to be unique for each user you could perhaps use a symlink for the file which then points to an autofs5 map with a $UID in it. You may need to use --bind mounts if it points to a LustreFS.

Daire

[Lustre-devel] Re-direction inodes

[Canon, Richard Shane]

I wrote something while at NERSC called CHOS that did something along
these lines but on a per process tree basis.  This allowed me to use a
common mount tree but then redirect certain paths based on the PID.  The
way I tackled it was with a symlink that existed in a /proc directory.
The symlink would resolve to different values depending on the PID that
was asking.  Children processes would inherit the same value unless they
explicitly changed it.  I don't know if this is of any use, but I just
thought I would mention it.

--Shane

-----Original Message-----
From: lustre-devel-bounces@lists.lustre.org
[mailto:lustre-devel-bounces at lists.lustre.org] On Behalf Of Andreas
Dilger
Sent: Monday, June 02, 2008 1:10 PM
To: Peter Braam
Cc: Nikita Danilov; lustre-devel at lists.lustre.org
Subject: Re: [Lustre-devel] Re-direction inodes

On Jun 02, 2008  08:59 +0900, Peter J. Braam wrote:
> I have a need in doing an architecture for a customer of a Lustre
client
> feature to have different data/page caches associated with an inode,
> depending on the user that accesses it.    So when a file is read,
user A
> will read different data from user B (assume the same for writes, but
I
> think this is a read-only feature).

Initially when I read this, I thought you were only trying to keep the
client-side cache separate, which could be done by adding the UID into
the inode lookup function for ll_test_inode() and treating these files
separately in the client-side cache.  That would be useful to avoid e.g.
user A reading "securefile" into memory, and user B being able to access
it from cache due to client-local access permissions allowing it.

> I remember that in the Coda file system we could easily re-direct I/O
to
> another inode using almost standard features in the VFS/page caches.
Is
> this still the case?  Would this work for the purpose I describe
above?

On later reading, it seems you want to have completely independent
file contents for each user, but they share the same pathname.  In some
filesystems it is possible to encode part of the pathname somewhat like:

	/home///$UID///file

but I think you are proposing a completely transparent mapping of
content:

alice> cat /etc/passwd
alice:x:1000:1000:Alice:/home/alice:/bin/bash

bob> cat /etc/passwd
bob:x:1001:1001:Bob:/home/bob:/bin/bash

correct?

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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