[Lustre-devel] Changelogs and xattrs

[Nathan Rutman]

On Aug 29, 2011, at 10:22 AM, "Kilian CAVALOTTI" <kilian.cavalotti.work at gmail.com> wrote:

> Hi all,
> 
> Using version 2.0, I noticed that changelogs emitted on extended
> attributes modification depend on the namespace the xattr belongs to.
...
> 
> So my questions are:
> 1. why are xattr changes ignored in namespaces other than user.*?
> 2. why xattr changes in {trusted,security,system}.* generate a CTIME
> event after the changelogs have been cleared? And not otherwise?
> 
The second question is actually easier - inode metadata changes (including xattr) generate CTIME events, but these are rate-limited to once per "clear" to avoid filling the logs on heavily used files. One TIME event per file in a log is sufficient to know that the file has been touched for eg backup or HSM purposes (but of course, not all purposes).  
Why only user xattrs are recorded was initially an attempt to avoid recording the "lustre." xattr changes that would potentially have been confusing to users, but perhaps we went too far here. I can't really think of any reason to avoid the other namespaces now. 

BTW, Xyratex has some improvements for changelog mtime handling that we'll push upstream. ______________________________________________________________________
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