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

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Submitter Davidlohr Bueso
Date Feb. 11, 2019, 4:15 p.m.
Message ID <20190211161529.uskq5ca7y3j5522i@linux-r8p5>
Download mbox | patch
Permalink /patch/723095/
State New
Headers show

Comments

Davidlohr Bueso - Feb. 11, 2019, 4:15 p.m.
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 <davem@davemloft.net>
Cc: Bjorn Topel <bjorn.topel@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@intel.com>
CC: netdev@vger.kernel.org
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 net/xdp/xdp_umem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
Björn Töpel - Feb. 11, 2019, 4:21 p.m.
Den mån 11 feb. 2019 kl 17:15 skrev Davidlohr Bueso <dave@stgolabs.net>:
>
> 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.
>

Thanks for the cleanup!

Acked-by: Björn Töpel <bjorn.topel@intel.com>

> 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
> Signed-off-by: Davidlohr Bueso <dbueso@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
>
Daniel Borkmann - Feb. 11, 2019, 7:53 p.m.
On 02/11/2019 05:15 PM, Davidlohr Bueso wrote:
> 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 <davem@davemloft.net>
> Cc: Bjorn Topel <bjorn.topel@intel.com>
> Cc: Magnus Karlsson <magnus.karlsson@intel.com>
> CC: netdev@vger.kernel.org
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

Applied, thanks!

Patch

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) {