Commit-ID: 73e10a61817dfc97fe7418bfad1f608e562d7348 Gitweb: http://git.kernel.org/tip/73e10a61817dfc97fe7418bfad1f608e562d7348 Author: Kirill A. Shutemov <kirill.shute...@linux.intel.com> AuthorDate: Thu, 16 Mar 2017 18:26:54 +0300 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Sat, 18 Mar 2017 09:48:03 +0100
mm/gup: Provide callback to check if __GUP_fast() is allowed for the range This is a preparation patch for the transition of x86 to the generic GUP_fast() implementation. On x86, get_user_pages_fast() does a couple of sanity checks to see if we can call __get_user_pages_fast() for the range. This kind of wrapping protection should be useful for the generic code too. Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Aneesh Kumar K . V <aneesh.ku...@linux.vnet.ibm.com> Cc: Borislav Petkov <b...@alien8.de> Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Dann Frazier <dann.fraz...@canonical.com> Cc: Dave Hansen <dave.han...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: Steve Capper <steve.cap...@linaro.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: linux-a...@vger.kernel.org Cc: linux...@kvack.org Link: http://lkml.kernel.org/r/20170316152655.37789-7-kirill.shute...@linux.intel.com [ Small readability edits. ] Signed-off-by: Ingo Molnar <mi...@kernel.org> --- mm/gup.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index e3d1e80..527ec2c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1614,6 +1614,21 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, return nr; } +#ifndef gup_fast_permitted +/* + * Check if it's allowed to use __get_user_pages_fast() for the range, or + * we need to fall back to the slow version: + */ +bool gup_fast_permitted(unsigned long start, int nr_pages, int write) +{ + unsigned long len, end; + + len = (unsigned long) nr_pages << PAGE_SHIFT; + end = start + len; + return end >= start; +} +#endif + /** * get_user_pages_fast() - pin user pages in memory * @start: starting user address @@ -1633,11 +1648,14 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { - int nr, ret; + int nr = 0, ret = 0; start &= PAGE_MASK; - nr = __get_user_pages_fast(start, nr_pages, write, pages); - ret = nr; + + if (gup_fast_permitted(start, nr_pages, write)) { + nr = __get_user_pages_fast(start, nr_pages, write, pages); + ret = nr; + } if (nr < nr_pages) { /* Try to get the remaining pages with get_user_pages */
