Ext3 users - Sep 2002 - querying the ext3 journal

I'm not sure if this question makes sense, but here goes.  We have the need
to periodically check for newly created/modified files in a rather elaborate
and well populated directory structure.  I don't believe that simply walking
the directory and checking stat's is the answer, given that I need a process
that will impose minimal performance degredation on the system.  Would it be
possible to query the journal itself for these changes?  Is there an API (or
better yet, an app) to do so?

Direct replies would be welcomed.  

Thanks in advance for any assistance on this,

Marc Wrona
Senior Software Engineer
Advertising.com (or www.advertising.com)
410-244-1370 x13754
We bring innovation to interactive communication.
Advertising.com - Superior Technology. Superior Performance. 




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Hi,

On Fri, Sep 13, 2002 at 11:11:02AM -0400, Marc Wrona
wrote:
> I'm not sure if this question makes sense, but here goes.  We have the
need
> to periodically check for newly created/modified files in a rather
elaborate
> and well populated directory structure.  I don't believe that simply
walking
> the directory and checking stat's is the answer, given that I need a
process
> that will impose minimal performance degredation on the system.  Would it
be
> possible to query the journal itself for these changes?  Is there an API
(or
> better yet, an app) to do so?
No, but there's a directory notify API which might be useful.  See
linux/Documentation/dnotify.txt in the Linux source code; there's also
the "fam" package which acts as a front-end to dnotify.

The journal entries in ext3 are quite short-lived.  They are only
guaranteed to stick around long enough for the writeback to disk to
occur.  The journal won't help you if you want to come back some time
later and see everything which has changed.

Cheers,
 Stephen

On Fri, 2002-09-13 at 17:11, Marc Wrona wrote:
> I'm not sure if this question makes sense, but here goes.  We have the
need
> to periodically check for newly created/modified files in a rather
elaborate
> and well populated directory structure.  I don't believe that simply
walking
> the directory and checking stat's is the answer, given that I need a
process
> that will impose minimal performance degredation on the system.  Would it
be
> possible to query the journal itself for these changes?  Is there an API
(or
> better yet, an app) to do so?
> 
> Direct replies would be welcomed.  
> 
Maybe fam (file alteration monitor) will suit your needs. It has kernel
cooperation for detection file/directory modifications. Many modern
distributions bundle it (for example RedHat 7.3). The nautilus file
manager uses that to automatically update the directory views.

Otherwise you can try the dnotify kernel facility (fam uses that if
present). Check the dnotify.txt file in the kernel sources.

Best

Diego
> Thanks in advance for any assistance on this,
> 
> Marc Wrona
> Senior Software Engineer
> Advertising.com (or www.advertising.com)
> 410-244-1370 x13754
> We bring innovation to interactive communication.
> Advertising.com - Superior Technology. Superior Performance. 
> 
> 
> 
> 
> ***********************************************************
> The information transmitted in this email is intended only for
> the person(s) or entity to which it is addressed and may
> contain confidential and/or privileged material.  Any review, 
> retransmission, dissemination or other use of, or taking of
> any action in reliance upon, this information by persons or
> entities other than the intended recipient is prohibited.
> If you received this email in error, please contact the
> sender and permanently delete the email from any computer.
> 
> 
> 
> _______________________________________________
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-- 
-------------------------------------------------------
Diego Santa Cruz
PhD. student
Publications available at http://ltswww.epfl.ch/~dsanta
Signal Processing Institute (LTS1 / ITS / STI)
Swiss Federal Institute of Technology (EPFL)
EPFL - STI - ITS, CH-1015 Lausanne, Switzerland
E-mail:     Diego.SantaCruz@epfl.ch
Phone:      +41 - 21 - 693 26 57
Fax:        +41 - 21 - 693 76 00
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