mm: add RCU annotation to pte_offset_map(_lock)

RCU lock is taken by ___pte_offset_map() unless it returns NULL.  Add this
information to its inline callers to avoid sparse warning about context
imbalance in pte_unmap().

Link: https://lkml.kernel.org/r/20241210000604.700710-1-oss@malat.biz
Signed-off-by: Petr Malat <oss@malat.biz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: petris

include/linux/mm.h

@@ -3010,7 +3010,15 @@ static inline void pagetable_pte_dtor(struct ptdesc *ptdesc)
 	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
 }
 
-pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
+pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
+static inline pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr,
+			pmd_t *pmdvalp)
+{
+	pte_t *pte;
+
+	__cond_lock(RCU, pte = ___pte_offset_map(pmd, addr, pmdvalp));
+	return pte;
+}
 static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
 {
 	return __pte_offset_map(pmd, addr, NULL);
@@ -3023,7 +3031,8 @@ static inline pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
 {
 	pte_t *pte;
 
-	__cond_lock(*ptlp, pte = __pte_offset_map_lock(mm, pmd, addr, ptlp));
+	__cond_lock(RCU, __cond_lock(*ptlp,
+			pte = __pte_offset_map_lock(mm, pmd, addr, ptlp)));
 	return pte;
 }
 

mm/pgtable-generic.c

@@ -279,7 +279,7 @@ static unsigned long pmdp_get_lockless_start(void) { return 0; }
 static void pmdp_get_lockless_end(unsigned long irqflags) { }
 #endif
 
-pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
+pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
 {
 	unsigned long irqflags;
 	pmd_t pmdval;