diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 64 |
1 files changed, 64 insertions, 0 deletions
@@ -1095,6 +1095,70 @@ long get_user_pages(unsigned long start, unsigned long nr_pages, } EXPORT_SYMBOL(get_user_pages); +#ifdef CONFIG_FS_DAX +/* + * This is the same as get_user_pages() in that it assumes we are + * operating on the current task's mm, but it goes further to validate + * that the vmas associated with the address range are suitable for + * longterm elevated page reference counts. For example, filesystem-dax + * mappings are subject to the lifetime enforced by the filesystem and + * we need guarantees that longterm users like RDMA and V4L2 only + * establish mappings that have a kernel enforced revocation mechanism. + * + * "longterm" == userspace controlled elevated page count lifetime. + * Contrast this to iov_iter_get_pages() usages which are transient. + */ +long get_user_pages_longterm(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas_arg) +{ + struct vm_area_struct **vmas = vmas_arg; + struct vm_area_struct *vma_prev = NULL; + long rc, i; + + if (!pages) + return -EINVAL; + + if (!vmas) { + vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *), + GFP_KERNEL); + if (!vmas) + return -ENOMEM; + } + + rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas); + + for (i = 0; i < rc; i++) { + struct vm_area_struct *vma = vmas[i]; + + if (vma == vma_prev) + continue; + + vma_prev = vma; + + if (vma_is_fsdax(vma)) + break; + } + + /* + * Either get_user_pages() failed, or the vma validation + * succeeded, in either case we don't need to put_page() before + * returning. + */ + if (i >= rc) + goto out; + + for (i = 0; i < rc; i++) + put_page(pages[i]); + rc = -EOPNOTSUPP; +out: + if (vmas != vmas_arg) + kfree(vmas); + return rc; +} +EXPORT_SYMBOL(get_user_pages_longterm); +#endif /* CONFIG_FS_DAX */ + /** * populate_vma_page_range() - populate a range of pages in the vma. * @vma: target vma |