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From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
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Subject: [PATCH v6 20/24] powerpc: book3s64: convert to pin_user_pages() and put_user_page()
Date: Tue, 19 Nov 2019 00:16:39 -0800
Message-ID: <20191119081643.1866232-21-jhubbard@nvidia.com>
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1. Convert from get_user_pages() to pin_user_pages().

2. As required by pin_user_pages(), release these pages via
put_user_page(). In this case, do so via put_user_pages_dirty_lock().

That has the side effect of calling set_page_dirty_lock(), instead
of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

3. Release each page in mem->hpages[] (instead of mem->hpas[]), because
that is the array that pin_longterm_pages() filled in. This is more
accurate and should be a little safer from a maintenance point of
view.

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 arch/powerpc/mm/book3s64/iommu_api.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s6=
4/iommu_api.c
index 56cc84520577..196383e8e5a9 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -103,7 +103,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, uns=
igned long ua,
 	for (entry =3D 0; entry < entries; entry +=3D chunk) {
 		unsigned long n =3D min(entries - entry, chunk);
=20
-		ret =3D get_user_pages(ua + (entry << PAGE_SHIFT), n,
+		ret =3D pin_user_pages(ua + (entry << PAGE_SHIFT), n,
 				FOLL_WRITE | FOLL_LONGTERM,
 				mem->hpages + entry, NULL);
 		if (ret =3D=3D n) {
@@ -167,9 +167,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, uns=
igned long ua,
 	return 0;
=20
 free_exit:
-	/* free the reference taken */
-	for (i =3D 0; i < pinned; i++)
-		put_page(mem->hpages[i]);
+	/* free the references taken */
+	put_user_pages(mem->hpages, pinned);
=20
 	vfree(mem->hpas);
 	kfree(mem);
@@ -212,10 +211,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group=
_mem_t *mem)
 		if (!page)
 			continue;
=20
-		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
-			SetPageDirty(page);
+		put_user_pages_dirty_lock(&mem->hpages[i], 1,
+					  MM_IOMMU_TABLE_GROUP_PAGE_DIRTY);
=20
-		put_page(page);
 		mem->hpas[i] =3D 0;
 	}
 }
--=20
2.24.0