[Xen-devel] [PATCH v3 19/41] vfio: convert put_page() to put_user_page*()

[john.hubbard@xxxxxxxxx]

From: John Hubbard <jhubbard@xxxxxxxxxx>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Note that this effectively changes the code's behavior in
qp_release_pages(): it now ultimately calls 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]

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

Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 054391f30fa8..5a5461a14299 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -320,9 +320,9 @@ static int put_pfn(unsigned long pfn, int prot)
 {
        if (!is_invalid_reserved_pfn(pfn)) {
                struct page *page = pfn_to_page(pfn);
-               if (prot & IOMMU_WRITE)
-                       SetPageDirty(page);
-               put_page(page);
+               bool dirty = prot & IOMMU_WRITE;
+
+               put_user_pages_dirty_lock(&page, 1, dirty);
                return 1;
        }
        return 0;
@@ -356,7 +356,7 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned 
long vaddr,
                 */
                if (ret > 0 && vma_is_fsdax(vmas[0])) {
                        ret = -EOPNOTSUPP;
-                       put_page(page[0]);
+                       put_user_page(page[0]);
                }
        }
        up_read(&mm->mmap_sem);
-- 
2.22.0


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