On 17.01.2021 00:34 Linus Torvalds wrote:
On Sat, Jan 16, 2021 at 3:05 PM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
I'll go think about this.
Martin, since you can apparently trigger the problem easily, hopefully
you're willing to try a couple of patches?
Hmm. It might end up being as simple as the attached patch.
I'm not super-happy with this situation (that whole nasty security
issue had some horrible cascading problems), and this only really
fixes _pinned_ pages.
In particular, somebody doing a plain get_user_pages() for writing can
still hit issues (admittedly that's true in general, but the vm
changes made it much more obviously true).
But for the case of io_uring buffers, this looks like the obvious simple fix.
I don't have a load to test this with, so I'll come back to ask Martin
to do so...
Linus
Thanks! With the patch (skip swapping pinned pages) the problem doesn't
occur anymore, so it seems to fix it.
