On Wed, 12 May 2021, Peter Xu wrote: > On Tue, Apr 27, 2021 at 12:12:53PM -0400, Peter Xu wrote: > > This is v2 of uffd-wp shmem & hugetlbfs support, which completes uffd-wp as a > > kernel full feature, as it only supports anonymous before this series. > > Ping.. > > Thinking about a repost, as this series shouldn't be able to apply after we've > got more relevant patches into -mm. E.g., the full minor fault, and also some > small stuff like pagemap, as we need one more patch to support shmem/hugetlbfs > too. > > Hugh, haven't received any further comment from you on shmem side (or on the > general idea). It would be great to still have some of your input. > > Let me know if you prefer to read a fresh new version otherwise. I am very sorry to let you down, Peter, repeatedly; but it is now very clear that I shall *never* have time to review your patchset - I am too slow, have too much else to attend to, and take too long each time to sink myself deep enough into userfaultfd. I realize that you're being considerate, and expecting no more than a few comments from me, rather than asking for formal review; but it's still too much for me to get into. The only reason I was involved at all, was when you were wondering how to handle the pagetable entries for shmem. I suggested one encoding, Andrea suggested slightly differently: Andrea's was more elegant (no "swap type" required), and it looked like you went with his - good. I wonder whether you noticed https://lore.kernel.org/linux-mm/20210407084238.20443-2-apopple@xxxxxxxxxx/ which might interfere. I've had no more time to look at that than yours, so no opinion on it (and I don't know what happened to it after that). Please keep uppermost in mind when modifying mm/shmem.c for userfaultfd, the difference between shared and private; and be on guard against the ways in which CONFIG_USERFAULTFD=y might open a door to abuse. Thanks, Hugh
