Hi Andrea, Thanks for the quick reply. That's great to hear that Peter has been working on those improvements. I didn't try the entire patchset but I did confirm that patch 13, not surprisingly, also resolves that issue on at least on x86: https://lkml.org/lkml/2019/9/26/179 Given that seems pretty low risk and it definitely resolves a pretty big issue for the non-cooperative userfaultfd case, any chance it could be landed ahead of the rest of the series? Thanks, Brian On Fri, Feb 14, 2020 at 6:20 PM Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > Hello, > > this and other enhancements have already implemented by Peter (CC'ed) > and in the right way, by altering the retry logic in the page fault > code. This is a requirement for other kind of usages too, notably the > UFFD_WRITEPROTECT ioctl after which multiple consecutive faults can > happen and must be handled. > > IIRC Kirill asked at last LSF-MM uffd-wp talk if there's any > particular reason the fault couldn't be retried currently. I had no > sure answer other than there's apparently no strong reason why > VM_FAULT_RETRY is only allowed 1 time currently, so there should be no > issue in lifting that artificial restriction. > > I'm running with this patchset applied in my systems since Nov with no > regression at all. I got sidetracked by various other issues, so > unfortunately I didn' post a proper reviewed-by on the last submit yet > (pending), but I did at least test it and it was rock solid so far. > > https://lore.kernel.org/lkml/20190926093904.5090-1-peterx@xxxxxxxxxx/ > > Can you test and verify it too if it solves your use case? > > Also note the complete uffd-WP support submit also from Peter: > > https://lore.kernel.org/lkml/20190620022008.19172-1-peterx@xxxxxxxxxx/ > > https://github.com/xzpeter/linux/tree/uffd-wp-merged > > Thanks, > Andrea >
