diff options
Diffstat (limited to 'include/linux/rmap.h')
| -rw-r--r-- | include/linux/rmap.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 20803fcb49a7..6cd020eea37a 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -449,6 +449,28 @@ static inline void __folio_rmap_sanity_checks(const struct folio *folio, default: VM_WARN_ON_ONCE(true); } + + /* + * Anon folios must have an associated live anon_vma as long as they're + * mapped into userspace. + * Note that the atomic_read() mainly does two things: + * + * 1. In KASAN builds with CONFIG_SLUB_RCU_DEBUG, it causes KASAN to + * check that the associated anon_vma has not yet been freed (subject + * to KASAN's usual limitations). This check will pass if the + * anon_vma's refcount has already dropped to 0 but an RCU grace + * period hasn't passed since then. + * 2. If the anon_vma has not yet been freed, it checks that the + * anon_vma still has a nonzero refcount (as opposed to being in the + * middle of an RCU delay for getting freed). + */ + if (folio_test_anon(folio) && !folio_test_ksm(folio)) { + unsigned long mapping = (unsigned long)folio->mapping; + struct anon_vma *anon_vma; + + anon_vma = (void *)(mapping - FOLIO_MAPPING_ANON); + VM_WARN_ON_FOLIO(atomic_read(&anon_vma->refcount) == 0, folio); + } } /* |