linux-kernel - [PATCH] drm/radeon: Convert get_user_pages() --> pin_user

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Message-Id: <1590526802-3008-1-git-send-email-jrdr.linux@gmail.com>
Date:   Wed, 27 May 2020 02:30:02 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     alexander.deucher@....com, christian.koenig@....com,
        David1.Zhou@....com, daniel@...ll.ch
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Souptick Joarder <jrdr.linux@...il.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH] drm/radeon: 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() + release_pages() 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: Souptick Joarder <jrdr.linux@...il.com>
Cc: John Hubbard <jhubbard@...dia.com>

Hi,

I'm compile tested this, but unable to run-time test, so any testing
help is much appriciated.
---
 drivers/gpu/drm/radeon/radeon_ttm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 5d50c9e..e927de2 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -506,7 +506,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 		uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE;
 		struct page **pages = ttm->pages + pinned;
 
-		r = get_user_pages(userptr, num_pages, write ? FOLL_WRITE : 0,
+		r = pin_user_pages(userptr, num_pages, write ? FOLL_WRITE : 0,
 				   pages, NULL);
 		if (r < 0)
 			goto release_pages;
@@ -535,7 +535,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 	kfree(ttm->sg);
 
 release_pages:
-	release_pages(ttm->pages, pinned);
+	unpin_user_pages(ttm->pages, pinned);
 	return r;
 }
 
@@ -562,7 +562,7 @@ static void radeon_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
 			set_page_dirty(page);
 
 		mark_page_accessed(page);
-		put_page(page);
+		unpin_user_page(page);
 	}
 
 	sg_free_table(ttm->sg);
-- 
1.9.1