Hi,
On Wed, Oct 18, 2000 at 03:23:17PM +0200, Andrea Arcangeli wrote:
> This change makes sense and I agree it would cover the problem. However I
> prefer to clarify that doing it for the swap cache as described is not nearly
> enough to cover the mm corruption (everything that gets written via a memory
> balancing mechanism should do the same).
>
> Said that I think it would be possible to do it for SHM and shared mappings too.
shm already does it: shm_swap_core returns RETRY unless page count is
1. file maps are close: file swapping already uses the address space
a_ops, but currently uses that at the wrong time: unmap time rather
than last-release. Rik?
> However this still makes me wonder why should we unmap the pte of a page that
> we can't free until we unmap_kiobuf? That's not as bad as having a
> nopage+swapout dummy operations in the sound driver DMA page case, because
> usually user-kiobufs are temporary just for the time of the DMA I/O, though.
It's no different from mlock(): if you've got some reason why one
specific mapping can't be unmapped (either it's locked or it is
inherently non-swappable like a kiobuf), then there's no reason to
make that per-mapping information visible at the per-page level.
We allow multiple processes to mlock() the same page, after all.
Cheers,
Stephen
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Oct 23 2000 - 21:00:13 EST