Hi Peter, I'll try helping out by giving the entire patchset a try. But in the meantime, if the plan of record will be to always allow retrying then shouldn't the block I mailed a patch on be removed regardless because do_user_addr_fault always starts with FAULT_FLAG_ALLOW_RETRY and we shouldn't ever land there without it in the future and allows userfaultfd to retry? Thanks, Brian On Mon, Feb 17, 2020 at 10:07 AM Peter Xu <peterx@xxxxxxxxxx> wrote: > > On Sat, Feb 15, 2020 at 09:29:46AM -0500, Brian Geffon wrote: > > 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 Andrea & Brian! Yes it would be great if the series (or some > of the patches) could be moved forward. Please just let me know if > there's still anything I can do from my side. > > Thanks, > > > > > 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 > > > > > > > -- > Peter Xu >
