linux-kernel - [PATCH 1/2] xsk: do not use mmap

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Message-Id: <20190207053740.26915-2-dave@stgolabs.net>
Date:   Wed,  6 Feb 2019 21:37:39 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, dave@...olabs.net,
        linux-kernel@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Bjorn Topel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        netdev@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 1/2] xsk: do not use mmap_sem

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 <davem@...emloft.net>
Cc: Bjorn Topel <bjorn.topel@...el.com>
Cc: Magnus Karlsson <magnus.karlsson@...el.com>
CC: netdev@...r.kernel.org
Signed-off-by: Davidlohr Bueso <dbueso@...e.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