[RFC 4/6] powerpc/mm/book3s64: Annotate the subpage-protection PTE lock

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

Clang's context analysis reports:
  subpage_prot.c:83:2: error: releasing spinlock 'ptl' that was not held [-Werror,-Wthread-safety-analysis]

pte_offset_map_lock() holds ptl when it returns a PTE and
pte_unmap_unlock() drops it. However since the lock is taken inside the
helper, which is not annotated, so the unlock in hpte_flush_range()
looks unheld.

This patch fixes it in hpte_flush_range() by adding the needed
annotation here. IMO, should ideally be added to pte_offset_map_lock(),
once that happens (since it might need larger enablement), we can remove
it from here.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/mm/book3s64/subpage_prot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c b/arch/powerpc/mm/book3s64/subpage_prot.c
index 37d47282c368..d641c35c408d 100644
--- a/arch/powerpc/mm/book3s64/subpage_prot.c
+++ b/arch/powerpc/mm/book3s64/subpage_prot.c
@@ -73,6 +73,8 @@ static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 	if (!pte)
 		return;
+	/* pte_offset_map_lock on success returns with ptl lock held */
+	__acquire(ptl);
 	lazy_mmu_mode_enable();
 	for (; npages > 0; --npages) {
 		pte_update(mm, addr, pte, 0, 0, 0);
--
2.39.5