diff options
Diffstat (limited to 'include/linux/file_ref.h')
| -rw-r--r-- | include/linux/file_ref.h | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/include/linux/file_ref.h b/include/linux/file_ref.h index 9b3a8d9b17ab..6ef92d765a66 100644 --- a/include/linux/file_ref.h +++ b/include/linux/file_ref.h @@ -61,6 +61,7 @@ static inline void file_ref_init(file_ref_t *ref, unsigned long cnt) atomic_long_set(&ref->refcnt, cnt - 1); } +bool __file_ref_put_badval(file_ref_t *ref, unsigned long cnt); bool __file_ref_put(file_ref_t *ref, unsigned long cnt); /** @@ -161,6 +162,39 @@ static __always_inline __must_check bool file_ref_put(file_ref_t *ref) } /** + * file_ref_put_close - drop a reference expecting it would transition to FILE_REF_NOREF + * @ref: Pointer to the reference count + * + * Semantically it is equivalent to calling file_ref_put(), but it trades lower + * performance in face of other CPUs also modifying the refcount for higher + * performance when this happens to be the last reference. + * + * For the last reference file_ref_put() issues 2 atomics. One to drop the + * reference and another to transition it to FILE_REF_DEAD. This routine does + * the work in one step, but in order to do it has to pre-read the variable which + * decreases scalability. + * + * Use with close() et al, stick to file_ref_put() by default. + */ +static __always_inline __must_check bool file_ref_put_close(file_ref_t *ref) +{ + long old, new; + + old = atomic_long_read(&ref->refcnt); + do { + if (unlikely(old < 0)) + return __file_ref_put_badval(ref, old); + + if (old == FILE_REF_ONEREF) + new = FILE_REF_DEAD; + else + new = old - 1; + } while (!atomic_long_try_cmpxchg(&ref->refcnt, &old, new)); + + return new == FILE_REF_DEAD; +} + +/** * file_ref_read - Read the number of file references * @ref: Pointer to the reference count * |