xsk: share the mmap_sem for page pinning

Davidlohr Bueso · borkmann · commit e451eb510684 · 2019-02-11T20:51:09.000+01:00
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: c0c77d8 ("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
@@ -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) {
