FOLL_LONGTERM suggests a pin which is going to be given to hardware and
can't move. It would truncate CMA permanently and should be excluded.
FOLL_LONGTERM has already been checked in the slow path, but not checked in
the fast path, which means a possible leak of CMA page to longterm pinned
requirement through this crack.
Place a check in gup_pte_range() in the fast path.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/gup.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index 766ae54..de1b03f 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1757,6 +1757,14 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
+ /*
+ * FOLL_LONGTERM suggests a pin given to hardware. Prevent it
+ * from truncating CMA area
+ */
+ if (unlikely(flags & FOLL_LONGTERM) &&
+ is_migrate_cma_page(page))
+ goto pte_unmap;
+
head = try_get_compound_head(page, 1);
if (!head)
goto pte_unmap;
@@ -1900,6 +1908,12 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
refs++;
} while (addr += PAGE_SIZE, addr != end);
+ if (unlikely(flags & FOLL_LONGTERM) &&
+ is_migrate_cma_page(page)) {
+ *nr -= refs;
+ return 0;
+ }
+
head = try_get_compound_head(pmd_page(orig), refs);
if (!head) {
*nr -= refs;
@@ -1941,6 +1955,12 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
refs++;
} while (addr += PAGE_SIZE, addr != end);
+ if (unlikely(flags & FOLL_LONGTERM) &&
+ is_migrate_cma_page(page)) {
+ *nr -= refs;
+ return 0;
+ }
+
head = try_get_compound_head(pud_page(orig), refs);
if (!head) {
*nr -= refs;
@@ -1978,6 +1998,12 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
refs++;
} while (addr += PAGE_SIZE, addr != end);
+ if (unlikely(flags & FOLL_LONGTERM) &&
+ is_migrate_cma_page(page)) {
+ *nr -= refs;
+ return 0;
+ }
+
head = try_get_compound_head(pgd_page(orig), refs);
if (!head) {
*nr -= refs;
--
2.7.5
