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From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
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Subject: [PATCH v2 10/19] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote()
Date: Mon, 25 Nov 2019 15:10:26 -0800
Message-ID: <20191125231035.1539120-11-jhubbard@nvidia.com>
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Convert process_vm_access to use the new pin_user_pages_remote()
call, which sets FOLL_PIN. Setting FOLL_PIN is now required for
code that requires tracking of pinned pages.

Also, release the pages via put_user_page*().

Also, rename "pages" to "pinned_pages", as this makes for
easier reading of process_vm_rw_single_vec().

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: J=C3=A9r=C3=B4me Glisse <jglisse@redhat.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/process_vm_access.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 357aa7bef6c0..fd20ab675b85 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -42,12 +42,11 @@ static int process_vm_rw_pages(struct page **pages,
 		if (copy > len)
 			copy =3D len;
=20
-		if (vm_write) {
+		if (vm_write)
 			copied =3D copy_page_from_iter(page, offset, copy, iter);
-			set_page_dirty_lock(page);
-		} else {
+		else
 			copied =3D copy_page_to_iter(page, offset, copy, iter);
-		}
+
 		len -=3D copied;
 		if (copied < copy && iov_iter_count(iter))
 			return -EFAULT;
@@ -96,7 +95,7 @@ static int process_vm_rw_single_vec(unsigned long addr,
 		flags |=3D FOLL_WRITE;
=20
 	while (!rc && nr_pages && iov_iter_count(iter)) {
-		int pages =3D min(nr_pages, max_pages_per_loop);
+		int pinned_pages =3D min(nr_pages, max_pages_per_loop);
 		int locked =3D 1;
 		size_t bytes;
=20
@@ -106,14 +105,15 @@ static int process_vm_rw_single_vec(unsigned long add=
r,
 		 * current/current->mm
 		 */
 		down_read(&mm->mmap_sem);
-		pages =3D get_user_pages_remote(task, mm, pa, pages, flags,
-					      process_pages, NULL, &locked);
+		pinned_pages =3D pin_user_pages_remote(task, mm, pa, pinned_pages,
+						     flags, process_pages,
+						     NULL, &locked);
 		if (locked)
 			up_read(&mm->mmap_sem);
-		if (pages <=3D 0)
+		if (pinned_pages <=3D 0)
 			return -EFAULT;
=20
-		bytes =3D pages * PAGE_SIZE - start_offset;
+		bytes =3D pinned_pages * PAGE_SIZE - start_offset;
 		if (bytes > len)
 			bytes =3D len;
=20
@@ -122,10 +122,12 @@ static int process_vm_rw_single_vec(unsigned long add=
r,
 					 vm_write);
 		len -=3D bytes;
 		start_offset =3D 0;
-		nr_pages -=3D pages;
-		pa +=3D pages * PAGE_SIZE;
-		while (pages)
-			put_page(process_pages[--pages]);
+		nr_pages -=3D pinned_pages;
+		pa +=3D pinned_pages * PAGE_SIZE;
+
+		/* If vm_write is set, the pages need to be made dirty: */
+		put_user_pages_dirty_lock(process_pages, pinned_pages,
+					  vm_write);
 	}
=20
 	return rc;
--=20
2.24.0