linux-kernel - [PATCH] drm/etnaviv: convert get_user_pages() --> pin_user

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Message-ID: <20200518054315.2407093-1-jhubbard@nvidia.com>
Date:   Sun, 17 May 2020 22:43:15 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     LKML <linux-kernel@...r.kernel.org>
CC:     Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        <etnaviv@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH] drm/etnaviv: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/

Signed-off-by: John Hubbard <jhubbard@...dia.com>
---

Hi,

Note that I have only compile-tested this patch, although that does
also include cross-compiling for a few other arches.

thanks,
John Hubbard
NVIDIA

 drivers/gpu/drm/etnaviv/etnaviv_gem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index dc9ef302f517..0f4578dc169d 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -675,10 +675,10 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
 		uint64_t ptr = userptr->ptr + pinned * PAGE_SIZE;
 		struct page **pages = pvec + pinned;
 
-		ret = get_user_pages_fast(ptr, num_pages,
+		ret = pin_user_pages_fast(ptr, num_pages,
 					  !userptr->ro ? FOLL_WRITE : 0, pages);
 		if (ret < 0) {
-			release_pages(pvec, pinned);
+			unpin_user_pages(pvec, pinned);
 			kvfree(pvec);
 			return ret;
 		}
@@ -702,7 +702,7 @@ static void etnaviv_gem_userptr_release(struct etnaviv_gem_object *etnaviv_obj)
 	if (etnaviv_obj->pages) {
 		int npages = etnaviv_obj->base.size >> PAGE_SHIFT;
 
-		release_pages(etnaviv_obj->pages, npages);
+		unpin_user_pages(etnaviv_obj->pages, npages);
 		kvfree(etnaviv_obj->pages);
 	}
 }
-- 
2.26.2