xsk: share the mmap_sem for page pinning

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.

Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Bjorn Topel <bjorn.topel@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@intel.com>
CC: netdev@vger.kernel.org
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index d4de871e7d4d7fa8f2c426559e92313c33d2655d..597866e7c44162a97b059abb384a41243b14ff2a 100644 (file)
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -259,10 +259,10 @@ 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,
-                             gup_flags, &umem->pgs[0], NULL);
-       up_write(&current->mm->mmap_sem);
+       down_read(&current->mm->mmap_sem);
+       npgs = get_user_pages_longterm(umem->address, umem->npgs,
+                                      gup_flags, &umem->pgs[0], NULL);
+       up_read(&current->mm->mmap_sem);
 
        if (npgs != umem->npgs) {
                if (npgs >= 0) {