Instead of scattering these assertions across the drivers, do this assertion inside the core of get_user_pages_fast*() functions. That also includes pin_user_pages_fast*() routines. Add a might_lock_read(mmap_sem) call to internal_get_user_pages_fast(). Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Michel Lespinasse <walken@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> --- Hi Andrew, This applies on top of [1], which in turn applies to today's (20200521) linux-next. As noted in the discussion [2], this will need changing from mmap_sem to mmap_lock, after Michel Lespinasse's patchset arrives. [1] https://lore.kernel.org/r/20200521233841.1279742-1-jhubbard@xxxxxxxxxx [2] https://lore.kernel.org/linux-mm/20200520124817.GG31189@xxxxxxxx/ thanks, John Hubbard NVIDIA mm/gup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index ada6aa79576dc..3462c076e8ecf 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2728,6 +2728,9 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, FOLL_FAST_ONLY))) return -EINVAL; + if (!(gup_flags & FOLL_FAST_ONLY)) + might_lock_read(¤t->mm->mmap_sem); + start = untagged_addr(start) & PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; -- 2.26.2
