linux-kernel - [PATCH 05/13] mm/frame-vector: Use FOLL

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Message-Id: <20201007164426.1812530-6-daniel.vetter@ffwll.ch>
Date:   Wed,  7 Oct 2020 18:44:18 +0200
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-media@...r.kernel.org,
        linux-s390@...r.kernel.org, Daniel Vetter <daniel.vetter@...ll.ch>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 05/13] mm/frame-vector: Use FOLL_LONGTERM

This is used by media/videbuf2 for persistent dma mappings, not just
for a single dma operation and then freed again, so needs
FOLL_LONGTERM.

Unfortunately current pup_locked doesn't support FOLL_LONGTERM due to
locking issues. Rework the code to pull the pup path out from the
mmap_sem critical section as suggested by Jason.

Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Pawel Osciak <pawel@...iak.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Kyungmin Park <kyungmin.park@...sung.com>
Cc: Tomasz Figa <tfiga@...omium.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Jérôme Glisse <jglisse@...hat.com>
Cc: Jan Kara <jack@...e.cz>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: linux-mm@...ck.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-samsung-soc@...r.kernel.org
Cc: linux-media@...r.kernel.org
---
 mm/frame_vector.c | 36 +++++++++++-------------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index 10f82d5643b6..39db520a51dc 100644
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -38,7 +38,6 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 	struct vm_area_struct *vma;
 	int ret = 0;
 	int err;
-	int locked;
 
 	if (nr_frames == 0)
 		return 0;
@@ -48,35 +47,22 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 
 	start = untagged_addr(start);
 
+	ret = pin_user_pages_fast(start, nr_frames,
+				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
+				  (struct page **)(vec->ptrs));
+	if (ret > 0) {
+		vec->got_ref = true;
+		vec->is_pfns = false;
+		goto out_unlocked;
+	}
+
 	mmap_read_lock(mm);
-	locked = 1;
 	vma = find_vma_intersection(mm, start, start + 1);
 	if (!vma) {
 		ret = -EFAULT;
 		goto out;
 	}
 
-	/*
-	 * While get_vaddr_frames() could be used for transient (kernel
-	 * controlled lifetime) pinning of memory pages all current
-	 * users establish long term (userspace controlled lifetime)
-	 * page pinning. Treat get_vaddr_frames() like
-	 * get_user_pages_longterm() and disallow it for filesystem-dax
-	 * mappings.
-	 */
-	if (vma_is_fsdax(vma)) {
-		ret = -EOPNOTSUPP;
-		goto out;
-	}
-
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
-		vec->got_ref = true;
-		vec->is_pfns = false;
-		ret = pin_user_pages_locked(start, nr_frames,
-			gup_flags, (struct page **)(vec->ptrs), &locked);
-		goto out;
-	}
-
 	vec->got_ref = false;
 	vec->is_pfns = true;
 	do {
@@ -101,8 +87,8 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 		vma = find_vma_intersection(mm, start, start + 1);
 	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
 out:
-	if (locked)
-		mmap_read_unlock(mm);
+	mmap_read_unlock(mm);
+out_unlocked:
 	if (!ret)
 		ret = -EFAULT;
 	if (ret > 0)
-- 
2.28.0