From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 4BC5E6B0069 for ; Tue, 14 Nov 2017 15:04:52 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id 70so10172034pgf.5 for ; Tue, 14 Nov 2017 12:04:52 -0800 (PST) Received: from mga07.intel.com (mga07.intel.com. [134.134.136.100]) by mx.google.com with ESMTPS id e4si16284597pgf.23.2017.11.14.12.04.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Nov 2017 12:04:50 -0800 (PST) Subject: [PATCH v2 1/4] mm: introduce get_user_pages_longterm From: Dan Williams Date: Tue, 14 Nov 2017 11:56:34 -0800 Message-ID: <151068939435.7446.13560129395419350737.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <151068938905.7446.12333914805308312313.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151068938905.7446.12333914805308312313.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Hellwig , stable@vger.kernel.org, linux-nvdimm@lists.01.org Until there is a solution to the dma-to-dax vs truncate problem it is not safe to allow long standing memory registrations against filesytem-dax vmas. Device-dax vmas do not have this problem and are explicitly allowed. This is temporary until a "memory registration with layout-lease" mechanism can be implemented for the affected sub-systems (RDMA and V4L2). Cc: Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Suggested-by: Christoph Hellwig Signed-off-by: Dan Williams --- include/linux/fs.h | 14 +++++++++++ include/linux/mm.h | 13 +++++++++++ mm/gup.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 91 insertions(+) diff --git a/include/linux/fs.h b/include/linux/fs.h index 57added3201d..0bacccc9461e 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3175,6 +3175,20 @@ static inline bool vma_is_dax(struct vm_area_struct *vma) return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); } +static inline bool vma_is_fsdax(struct vm_area_struct *vma) +{ + struct inode *inode; + + if (!vma->vm_file) + return false; + if (!vma_is_dax(vma)) + return false; + inode = file_inode(vma->vm_file); + if (inode->i_mode == S_IFCHR) + return false; /* device-dax */ + return true; +} + static inline int iocb_flags(struct file *file) { int res = 0; diff --git a/include/linux/mm.h b/include/linux/mm.h index 8d9f52a84f77..34ff8830f717 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1369,6 +1369,19 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, int *locked); long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, struct page **pages, unsigned int gup_flags); +#ifdef CONFIG_FS_DAX +long get_user_pages_longterm(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas); +#else +static inline long get_user_pages_longterm(unsigned long start, + unsigned long nr_pages, unsigned int gup_flags, + struct page **pages, struct vm_area_struct **vmas) +{ + return get_user_pages(start, nr_pages, gup_flags, pages, vmas); +} +#endif /* CONFIG_FS_DAX */ + int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages); diff --git a/mm/gup.c b/mm/gup.c index b2b4d4263768..ad9d13987f14 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -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 = kzalloc(sizeof(struct vm_area_struct *) * nr_pages, + 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org