[PATCH 3/4] s390/mm: Add __context_unsafe() attribute to gmap helper functions

[Heiko Carstens <hca@linux.ibm.com>]

Disable context analysis for various gmap helper functions to get rid
of a few warnings:

arch/s390/mm/gmap_helpers.c:80:1: warning: spinlock 'ptl' is not held on every path through here
arch/s390/mm/gmap_helpers.c:116:2: warning: releasing spinlock 'ptl' that was not held
arch/s390/mm/gmap_helpers.c:186:2: warning: releasing spinlock 'ptl' that was not held

Use __context_unsafe() to give a short comment why for function context
analysis is disabled.

try_get_locked_pte() is disabled since it may return a nonull value
regardless if it returns with a lock held or not.

This cannot be reflected with the context analysis attributes. It is
however possible to workaround this e.g. by adding a another `contended`
function parameter, however this would lead to the next problem:
pte_unmap_unlock() is a macro and therefore doesn't come with the
required context analysis attribute to address this.

For that reason also disable context analysis for
gmap_helper_zap_one_page() and gmap_helper_try_set_pte_unused()
until this has been addressed.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/mm/gmap_helpers.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/s390/mm/gmap_helpers.c b/arch/s390/mm/gmap_helpers.c
index 4bf7c9012feb..f910c9584560 100644
--- a/arch/s390/mm/gmap_helpers.c
+++ b/arch/s390/mm/gmap_helpers.c
@@ -40,6 +40,7 @@
  *   and locked.
  */
 pte_t *try_get_locked_pte(struct mm_struct *mm, unsigned long vmaddr, spinlock_t **ptl)
+__context_unsafe(/* Returns nonnull if lock taken or not taken */)
 {
 	pmd_t *pmdp, pmd, pmdval;
 	pud_t *pudp, pud;
@@ -90,6 +91,7 @@ EXPORT_SYMBOL_GPL(try_get_locked_pte);
  * Context: needs to be called while holding the mmap lock.
  */
 void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr)
+__context_unsafe(/* pte_unmap_unlock() not instrumented */)
 {
 	struct vm_area_struct *vma;
 	spinlock_t *ptl;	/* Lock for the host (userspace) page table */
@@ -161,6 +163,7 @@ EXPORT_SYMBOL_GPL(gmap_helper_discard);
  *          disabled.
  */
 void gmap_helper_try_set_pte_unused(struct mm_struct *mm, unsigned long vmaddr)
+__context_unsafe(/* pte_unmap_unlock() not instrumented */)
 {
 	spinlock_t *ptl;	/* Lock for the host (userspace) page table */
 	pte_t *ptep;
-- 
2.53.0