Re: [PATCH] get rid of vm_private_data and win posix shm
Richard Gooch (rgooch@ras.ucalgary.ca)
Wed, 29 Dec 1999 17:00:43 -0700
Linus Torvalds writes:
> In article <qwwd7rrgeen.fsf@sap.com>,
> Christoph Rohland <hans-christoph.rohland@sap.com> wrote:
> >
> >I implemented posix shm with its own namespace by extending filp_open
> >and do_unlink by an additional parameter for the root inode.
>
> Beautiful patch _except_ for this case. I'm really pleased with how well
> the POSIX shm code seems to integrate into the FS and VM layers, and
> that makes me happy.
>
> The one imbalance you added makes me cringe, though. I think we should
> just export it as a real filesystem, and mount it in a standard
> location. Nothing clever, just come up with a new location that is
> fixed and acceptable to all, kind of like /proc is now.
>
> That has the added advantage that you can eventually write scripts with
> perl etc to look at shared memory regions etc, without having to add new
> magic system calls.
>
> So how about standardizing on a base path called "//posix/shm"? Right
> now that is the same as "/posix/shm", but leave the double slash there
> in the utilities and library routines, because maybe we'll end up using
> the POSIX-approved "initial double slash is special" rule at some point
> in the future. So we can initially mount it as a regular mount-point,
> and then in the future maybe extend the notion of '//'-paths to be more
> of a "virtual filesystem" thing without breaking backwards
> compatibility.
>
> And don't worry about making "readdir()" and friends work yet - a
> minimalistic shm filesystem that only knows "lookup", "create" and
> "unlink" is fine, with the nice finishing touches can be left for
> later..
A year and a half ago I wrote the user-space API which would make use
of Eric Biederman's shmfs. This same code will work nicely with this
new implementation. Let me know where it ends up being mounted and
when it goes into the kernel, and I'll dust off the user-space code
and make it available again. It would be nice to finally have POSIX
SHM.
Regards,
Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca
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