[PATCH v2] xsk: share the mmap_sem for page pinning

[Davidlohr Bueso]

Holding mmap_sem exclusively for a gup() is an overkill.
Lets share the lock and replace the gup call for gup_longterm(),
as it is better suited for the lifetime of the pinning.

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, 3 insertions(+), 3 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 5ab236c5c9a5..e7fa8d0d7090 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -265,10 +265,10 @@ 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,
+       down_read(&current->mm->mmap_sem);
+       npgs = get_user_pages_longterm(umem->address, umem->npgs,
                              gup_flags, &umem->pgs[0], NULL);
-       up_write(&current->mm->mmap_sem);
+       up_read(&current->mm->mmap_sem);

        if (npgs != umem->npgs) {
                if (npgs >= 0) {
--
2.16.4