diff options
Diffstat (limited to 'include/linux/file_ref.h')
| -rw-r--r-- | include/linux/file_ref.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/include/linux/file_ref.h b/include/linux/file_ref.h index 9b3a8d9b17ab..31551e4cb8f3 100644 --- a/include/linux/file_ref.h +++ b/include/linux/file_ref.h @@ -161,6 +161,33 @@ 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; + + old = atomic_long_read(&ref->refcnt); + if (likely(old == FILE_REF_ONEREF)) { + if (likely(atomic_long_try_cmpxchg(&ref->refcnt, &old, FILE_REF_DEAD))) + return true; + } + return file_ref_put(ref); +} + +/** * file_ref_read - Read the number of file references * @ref: Pointer to the reference count * @@ -174,4 +201,18 @@ static inline unsigned long file_ref_read(file_ref_t *ref) return c >= FILE_REF_RELEASED ? 0 : c + 1; } +/* + * __file_ref_read_raw - Return the value stored in ref->refcnt + * @ref: Pointer to the reference count + * + * Return: The raw value found in the counter + * + * A hack for file_needs_f_pos_lock(), you probably want to use + * file_ref_read() instead. + */ +static inline unsigned long __file_ref_read_raw(file_ref_t *ref) +{ + return atomic_long_read(&ref->refcnt); +} + #endif |