[PATCH rc] mm/gup: use unpin_user_pages() in check_and_migrate_cma_pages()

[Jason Gunthorpe <jgg@nvidia.com>]

When FOLL_PIN is passed to __get_user_pages() the page list must be put
back using unpin_user_pages() otherwise the page pin reference persists in
a corrupted state.

Cc: <stable@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 mm/gup.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

I don't have any way to test CMA stuff, this was noticed by inspection.

diff --git a/mm/gup.c b/mm/gup.c
index 1bb349e5ed212a..2e26757f3c9276 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1630,8 +1630,11 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 		/*
 		 * drop the above get_user_pages reference.
 		 */
-		for (i = 0; i < nr_pages; i++)
-			put_page(pages[i]);
+		if (gup_flags & FOLL_PIN)
+			unpin_user_pages(pages, nr_pages);
+		else
+			for (i = 0; i < nr_pages; i++)
+				put_page(pages[i]);
 
 		if (migrate_pages(&cma_page_list, alloc_migration_target, NULL,
 			(unsigned long)&mtc, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
-- 
2.28.0