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SubjectRe: RO --bind mount implementation ...
On Tue, Aug 05, 2003 at 05:59:24PM +0100, viro@parcelfarce.linux.theplanet.co.uk wrote:
> On Tue, Aug 05, 2003 at 12:16:15AM +0200, Herbert Pötzl wrote:
>
> > anyway, I discussed this with some friends, and
> > they pointed out that this would be useful ...
> > so here is the first try ...
>
> Umm... You know, the most obvious system call that should care about
> read-only is open(pathname, O_RDWR) ;-) IOW, taking care of directory
> modifications is not enough - you need to deal with
> * opening file for write
> * truncation (both from *truncate() and from open() with O_TRUNC)
> * metadata changes (timestamps, ownership, permissions)

well, the open case, IMHO is handled by the
lookup_create() modifications, truncate is something
I obviously missed (I missed the intermezzo copies
too ;) and metadata changes were intentionally ignored
(it's the first try, and I'm glad that you see it as
a step in the right direction?)

> But yes, it's not that far from where we should eventualy get.

will add the truncate() case soon, maybe it is also
possible to move some parts of the may_create
function to the mnt_may_create (any suggestions for
a better name?), to avoid doing some checks twice ...

any further suggestions?

best,
Herbert

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