| Message ID | 20191125003715.516290-2-jhubbard@nvidia.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | mm/gup + IB: allow FOLL_FORCE for gup_fast and use in IB | expand |
diff --git a/mm/gup.c b/mm/gup.c index 8f236a335ae9..745b4036cdfd 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2401,7 +2401,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, unsigned long addr, len, end; int nr = 0, ret = 0; - if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE))) return -EINVAL; start = untagged_addr(start) & PAGE_MASK;
Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast(). This, combined with the fact that get_user_pages_fast() falls back to "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation: if you need FOLL_FORCE, you cannot call get_user_pages_fast(). There does not appear to be any reason for filtering out FOLL_FORCE. There is nothing in the _fast() implementation that requires that we avoid writing to the pages. So it appears to have been an oversight. Fix by allowing FOLL_FORCE to be set for get_user_pages_fast(). Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags") Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: John Hubbard <jhubbard@nvidia.com> --- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)