1. Convert from get_user_pages(FOLL_LONGTERM) to pin_longterm_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.gb...@lst.de

Signed-off-by: John Hubbard <jhubb...@nvidia.com>
---
 arch/powerpc/mm/book3s64/iommu_api.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/iommu_api.c 
b/arch/powerpc/mm/book3s64/iommu_api.c
index 56cc84520577..69d79cb50d47 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -103,9 +103,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, 
unsigned long ua,
        for (entry = 0; entry < entries; entry += chunk) {
                unsigned long n = min(entries - entry, chunk);
 
-               ret = get_user_pages(ua + (entry << PAGE_SHIFT), n,
-                               FOLL_WRITE | FOLL_LONGTERM,
-                               mem->hpages + entry, NULL);
+               ret = pin_longterm_pages(ua + (entry << PAGE_SHIFT), n,
+                                        FOLL_WRITE, mem->hpages + entry, NULL);
                if (ret == n) {
                        pinned += n;
                        continue;
@@ -167,9 +166,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, 
unsigned long ua,
        return 0;
 
 free_exit:
-       /* free the reference taken */
-       for (i = 0; i < pinned; i++)
-               put_page(mem->hpages[i]);
+       /* free the references taken */
+       put_user_pages(mem->hpages, pinned);
 
        vfree(mem->hpas);
        kfree(mem);
@@ -212,10 +210,9 @@ static void mm_iommu_unpin(struct 
mm_iommu_table_group_mem_t *mem)
                if (!page)
                        continue;
 
-               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);
 
-               put_page(page);
                mem->hpas[i] = 0;
        }
 }
-- 
2.24.0

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