On Tue, Nov 12, 2019 at 3:43 PM Jason Gunthorpe jgg@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 jhubbard@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.