Re: What's a realistic size for xattr?

[Charles Manning <manningc2@actrix.gen.nz>]

On Thursday 13 March 2008 12:32:33 Dave Quigley wrote:
> On Thu, 2008-03-13 at 11:06 +1300, Charles Manning wrote:
> > I'm trying to figure out a reasonable approach to implementing xattr in
> > YAFFS.
> >
> > >From my (limited) knowledge of xattr it seems that in theory you could
> > > store a
> >
> > multi-Mbyte database in xattr, but in practice a smaller size is far more
> > reasonable. Clearly storing/managing a small blob is going to be a lot
> > simpler.
> >
> > What is the cut off of a reasonable xattr blob size? 1kbytes? 2kbytes?...
> >
> > Thanx.
> >
> > Charles
> >
> >
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>
> I just realized that I never really answered your question. I've yet to
> see a reasonable SELinux context over 128 characters and Smack labels
> should be shorter than that. I don't know what beagle places in xattrs
> but I think that would be a good place to take a look for more practical
> xattr sizes.
>
> Dave


Is that 128 characters per xattr value or for the whole set of xattribs 
attached to a file?

What I'm trying to figure out is a reasonable size for all the xattribs 
together. ie. If I store xattribs as a single blob containing all the 
name:value pairs, how big will that blob need to be?

I should have perhaps given some extra context here.

I'm trying to find the bang-for-bucks trade-off point for a simple 
implementation.

YAFFS is a flash file system and is typically used in embedded systems 
(phones, routers, printers, point-of-sale,... etc). I guess limited use of 
SELinux is a reasonable benchmark for what is used here.

Huge fs for corporate servers don't really fit in this picture so I guess 
vastly complex ACLs , while theoretically possible, don't really fall into 
the yaffs space.