netdev - [PATCH v2 17/34] vfio: convert put_page() to put_user

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Date:   Sun,  4 Aug 2019 15:48:58 -0700
From:   john.hubbard@...il.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jérôme Glisse <jglisse@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org, ceph-devel@...r.kernel.org,
        devel@...verdev.osuosl.org, devel@...ts.orangefs.org,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-mm@...ck.org,
        linux-nfs@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org, linux-xfs@...r.kernel.org,
        netdev@...r.kernel.org, rds-devel@....oracle.com,
        sparclinux@...r.kernel.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, John Hubbard <jhubbard@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>
Subject: [PATCH v2 17/34] vfio: convert put_page() to put_user_page*()

From: John Hubbard <jhubbard@...dia.com>

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@lst.de

Cc: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org
Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
 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