On Fri, Apr 28, 2023 at 11:56:55AM -0400, Peter Xu wrote: > > PageAnon(page) can be called from GUP-fast after grabbing a reference. See > > gup_must_unshare(). > > Hmm.. Is it a good idea at all to sacrifise all "!anon" fast-gups for this? > People will silently got degrade even on legal pins on shmem/hugetlb, I > think, which seems to be still a very major use case. Remember gup fast was like this until quite recently - DAX wrecked it. I fixed it when I changed DAX to not post-scan the VMA list.. I'm not sure longterm and really fast need to go together. Jason
