On Tue, Nov 12, 2019 at 3:43 PM Jason Gunthorpe <j...@ziepe.ca> wrote: > > On Tue, Nov 12, 2019 at 02:45:51PM -0800, Dan Williams wrote: > > On Tue, Nov 12, 2019 at 2:43 PM John Hubbard <jhubb...@nvidia.com> wrote: > > > > > > On 11/12/19 12:43 PM, Jason Gunthorpe wrote: > > > ... > > > >> - } > > > >> + ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | > > > >> FOLL_LONGTERM, > > > >> + page, vmas, NULL); > > > >> + /* > > > >> + * The lifetime of a vaddr_get_pfn() page pin is > > > >> + * userspace-controlled. In the fs-dax case this could > > > >> + * lead to indefinite stalls in filesystem operations. > > > >> + * Disallow attempts to pin fs-dax pages via this > > > >> + * interface. > > > >> + */ > > > >> + if (ret > 0 && vma_is_fsdax(vmas[0])) { > > > >> + ret = -EOPNOTSUPP; > > > >> + put_page(page[0]); > > > >> } > > > > > > > > AFAIK this chunk is redundant now as it is some hack to emulate > > > > FOLL_LONGTERM? So vmas can be deleted too. > > > > > > Let me first make sure I understand what Dan has in mind for the vma > > > checking, in the other thread... > > > > It's not redundant relative to upstream which does not do anything the > > FOLL_LONGTERM in the gup-slow path... but I have not looked at patches > > 1-7 to see if something there made it redundant. > > Oh, the hunk John had below for get_user_pages_remote() also needs to > call __gup_longterm_locked() when FOLL_LONGTERM is specified, then > that calls check_dax_vmas() which duplicates the vma_is_fsdax() check > above.
Oh true, good eye. It is redundant if it does additionally call __gup_longterm_locked(), and it needs to do that otherwises it undoes the CMA migration magic that Aneesh added. > > Certainly no caller of FOLL_LONGTERM should have to do dax specific > VMA checking. Agree, that was my comment about cleaning up the vma_is_fsdax() check to be internal to the gup core. _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel