[PATCH 1/2] xsk: do not use mmap_sem

[Davidlohr Bueso]

Holding mmap_sem exclusively for a gup() is an overkill.
Lets replace the call for gup_fast() and let the mm take
it if necessary.

Cc: David S. Miller <da...@davemloft.net>
Cc: Bjorn Topel <bjorn.to...@intel.com>
Cc: Magnus Karlsson <magnus.karls...@intel.com>
CC: netdev@vger.kernel.org
Signed-off-by: Davidlohr Bueso <dbu...@suse.de>
---
 net/xdp/xdp_umem.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 5ab236c5c9a5..25e1e76654a8 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -265,10 +265,8 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem)
        if (!umem->pgs)
                return -ENOMEM;
 
-       down_write(&current->mm->mmap_sem);
-       npgs = get_user_pages(umem->address, umem->npgs,
-                             gup_flags, &umem->pgs[0], NULL);
-       up_write(&current->mm->mmap_sem);
+       npgs = get_user_pages_fast(umem->address, umem->npgs,
+                                  gup_flags, &umem->pgs[0]);
 
        if (npgs != umem->npgs) {
                if (npgs >= 0) {
-- 
2.16.4