Re: [PATCH 3/9] percpu_ref: replace pcpu_ prefix with percpu_

[Kent Overstreet]

On Tue, Sep 23, 2014 at 01:55:12AM -0400, Tejun Heo wrote:
> percpu_ref uses pcpu_ prefix for internal stuff and percpu_ for
> externally visible ones.  This is the same convention used in the
> percpu allocator implementation.  It works fine there but percpu_ref
> doesn't have too much internal-only stuff and scattered usages of
> pcpu_ prefix are confusing than helpful.
> 
> This patch replaces all pcpu_ prefixes with percpu_.  This is pure
> rename and there's no functional change.  Note that PCPU_REF_DEAD is
> renamed to __PERCPU_REF_DEAD to signify that the flag is internal.
> 
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>

Reviewed-by: Kent Overstreet <kmo@xxxxxxxxxxxxx>

> ---
>  include/linux/percpu-refcount.h | 46 ++++++++++++++++-----------------
>  lib/percpu-refcount.c           | 56 +++++++++++++++++++++--------------------
>  2 files changed, 52 insertions(+), 50 deletions(-)
> 
> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
> index d44b027..3d463a3 100644
> --- a/include/linux/percpu-refcount.h
> +++ b/include/linux/percpu-refcount.h
> @@ -13,7 +13,7 @@
>   *
>   * The refcount will have a range of 0 to ((1U << 31) - 1), i.e. one bit less
>   * than an atomic_t - this is because of the way shutdown works, see
> - * percpu_ref_kill()/PCPU_COUNT_BIAS.
> + * percpu_ref_kill()/PERCPU_COUNT_BIAS.
>   *
>   * Before you call percpu_ref_kill(), percpu_ref_put() does not check for the
>   * refcount hitting 0 - it can't, if it was in percpu mode. percpu_ref_kill()
> @@ -60,7 +60,7 @@ struct percpu_ref {
>  	 * The low bit of the pointer indicates whether the ref is in percpu
>  	 * mode; if set, then get/put will manipulate the atomic_t.
>  	 */
> -	unsigned long		pcpu_count_ptr;
> +	unsigned long		percpu_count_ptr;
>  	percpu_ref_func_t	*release;
>  	percpu_ref_func_t	*confirm_kill;
>  	struct rcu_head		rcu;
> @@ -88,26 +88,26 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
>  	return percpu_ref_kill_and_confirm(ref, NULL);
>  }
>  
> -#define PCPU_REF_DEAD		1
> +#define __PERCPU_REF_DEAD	1
>  
>  /*
>   * Internal helper.  Don't use outside percpu-refcount proper.  The
>   * function doesn't return the pointer and let the caller test it for NULL
>   * because doing so forces the compiler to generate two conditional
> - * branches as it can't assume that @ref->pcpu_count is not NULL.
> + * branches as it can't assume that @ref->percpu_count is not NULL.
>   */
> -static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
> -				    unsigned long __percpu **pcpu_countp)
> +static inline bool __percpu_ref_alive(struct percpu_ref *ref,
> +				      unsigned long __percpu **percpu_countp)
>  {
> -	unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
> +	unsigned long percpu_ptr = ACCESS_ONCE(ref->percpu_count_ptr);
>  
>  	/* paired with smp_store_release() in percpu_ref_reinit() */
>  	smp_read_barrier_depends();
>  
> -	if (unlikely(pcpu_ptr & PCPU_REF_DEAD))
> +	if (unlikely(percpu_ptr & __PERCPU_REF_DEAD))
>  		return false;
>  
> -	*pcpu_countp = (unsigned long __percpu *)pcpu_ptr;
> +	*percpu_countp = (unsigned long __percpu *)percpu_ptr;
>  	return true;
>  }
>  
> @@ -121,12 +121,12 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
>   */
>  static inline void percpu_ref_get(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count;
> +	unsigned long __percpu *percpu_count;
>  
>  	rcu_read_lock_sched();
>  
> -	if (__pcpu_ref_alive(ref, &pcpu_count))
> -		this_cpu_inc(*pcpu_count);
> +	if (__percpu_ref_alive(ref, &percpu_count))
> +		this_cpu_inc(*percpu_count);
>  	else
>  		atomic_long_inc(&ref->count);
>  
> @@ -144,13 +144,13 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
>   */
>  static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count;
> +	unsigned long __percpu *percpu_count;
>  	int ret;
>  
>  	rcu_read_lock_sched();
>  
> -	if (__pcpu_ref_alive(ref, &pcpu_count)) {
> -		this_cpu_inc(*pcpu_count);
> +	if (__percpu_ref_alive(ref, &percpu_count)) {
> +		this_cpu_inc(*percpu_count);
>  		ret = true;
>  	} else {
>  		ret = atomic_long_inc_not_zero(&ref->count);
> @@ -178,13 +178,13 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>   */
>  static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count;
> +	unsigned long __percpu *percpu_count;
>  	int ret = false;
>  
>  	rcu_read_lock_sched();
>  
> -	if (__pcpu_ref_alive(ref, &pcpu_count)) {
> -		this_cpu_inc(*pcpu_count);
> +	if (__percpu_ref_alive(ref, &percpu_count)) {
> +		this_cpu_inc(*percpu_count);
>  		ret = true;
>  	}
>  
> @@ -204,12 +204,12 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
>   */
>  static inline void percpu_ref_put(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count;
> +	unsigned long __percpu *percpu_count;
>  
>  	rcu_read_lock_sched();
>  
> -	if (__pcpu_ref_alive(ref, &pcpu_count))
> -		this_cpu_dec(*pcpu_count);
> +	if (__percpu_ref_alive(ref, &percpu_count))
> +		this_cpu_dec(*percpu_count);
>  	else if (unlikely(atomic_long_dec_and_test(&ref->count)))
>  		ref->release(ref);
>  
> @@ -226,9 +226,9 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
>   */
>  static inline bool percpu_ref_is_zero(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count;
> +	unsigned long __percpu *percpu_count;
>  
> -	if (__pcpu_ref_alive(ref, &pcpu_count))
> +	if (__percpu_ref_alive(ref, &percpu_count))
>  		return false;
>  	return !atomic_long_read(&ref->count);
>  }
> diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
> index 8ef3f5c..5aea6b7 100644
> --- a/lib/percpu-refcount.c
> +++ b/lib/percpu-refcount.c
> @@ -11,8 +11,8 @@
>   * percpu counters will all sum to the correct value
>   *
>   * (More precisely: because moduler arithmatic is commutative the sum of all the
> - * pcpu_count vars will be equal to what it would have been if all the gets and
> - * puts were done to a single integer, even if some of the percpu integers
> + * percpu_count vars will be equal to what it would have been if all the gets
> + * and puts were done to a single integer, even if some of the percpu integers
>   * overflow or underflow).
>   *
>   * The real trick to implementing percpu refcounts is shutdown. We can't detect
> @@ -29,11 +29,12 @@
>   * atomic_long_t can't hit 0 before we've added up all the percpu refs.
>   */
>  
> -#define PCPU_COUNT_BIAS		(1LU << (BITS_PER_LONG - 1))
> +#define PERCPU_COUNT_BIAS	(1LU << (BITS_PER_LONG - 1))
>  
> -static unsigned long __percpu *pcpu_count_ptr(struct percpu_ref *ref)
> +static unsigned long __percpu *percpu_count_ptr(struct percpu_ref *ref)
>  {
> -	return (unsigned long __percpu *)(ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> +	return (unsigned long __percpu *)
> +		(ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);
>  }
>  
>  /**
> @@ -51,10 +52,11 @@ static unsigned long __percpu *pcpu_count_ptr(struct percpu_ref *ref)
>  int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,
>  		    gfp_t gfp)
>  {
> -	atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> +	atomic_long_set(&ref->count, 1 + PERCPU_COUNT_BIAS);
>  
> -	ref->pcpu_count_ptr = (unsigned long)alloc_percpu_gfp(unsigned long, gfp);
> -	if (!ref->pcpu_count_ptr)
> +	ref->percpu_count_ptr =
> +		(unsigned long)alloc_percpu_gfp(unsigned long, gfp);
> +	if (!ref->percpu_count_ptr)
>  		return -ENOMEM;
>  
>  	ref->release = release;
> @@ -74,11 +76,11 @@ EXPORT_SYMBOL_GPL(percpu_ref_init);
>   */
>  void percpu_ref_exit(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> +	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
>  
> -	if (pcpu_count) {
> -		free_percpu(pcpu_count);
> -		ref->pcpu_count_ptr = PCPU_REF_DEAD;
> +	if (percpu_count) {
> +		free_percpu(percpu_count);
> +		ref->percpu_count_ptr = __PERCPU_REF_DEAD;
>  	}
>  }
>  EXPORT_SYMBOL_GPL(percpu_ref_exit);
> @@ -86,14 +88,14 @@ EXPORT_SYMBOL_GPL(percpu_ref_exit);
>  static void percpu_ref_kill_rcu(struct rcu_head *rcu)
>  {
>  	struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);
> -	unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> +	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
>  	unsigned long count = 0;
>  	int cpu;
>  
>  	for_each_possible_cpu(cpu)
> -		count += *per_cpu_ptr(pcpu_count, cpu);
> +		count += *per_cpu_ptr(percpu_count, cpu);
>  
> -	pr_debug("global %ld pcpu %ld",
> +	pr_debug("global %ld percpu %ld",
>  		 atomic_long_read(&ref->count), (long)count);
>  
>  	/*
> @@ -108,7 +110,7 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
>  	 * reaching 0 before we add the percpu counts. But doing it at the same
>  	 * time is equivalent and saves us atomic operations:
>  	 */
> -	atomic_long_add((long)count - PCPU_COUNT_BIAS, &ref->count);
> +	atomic_long_add((long)count - PERCPU_COUNT_BIAS, &ref->count);
>  
>  	WARN_ONCE(atomic_long_read(&ref->count) <= 0,
>  		  "percpu ref (%pf) <= 0 (%ld) after killed",
> @@ -143,10 +145,10 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
>  void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
>  				 percpu_ref_func_t *confirm_kill)
>  {
> -	WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
> +	WARN_ONCE(ref->percpu_count_ptr & __PERCPU_REF_DEAD,
>  		  "%s called more than once on %pf!", __func__, ref->release);
>  
> -	ref->pcpu_count_ptr |= PCPU_REF_DEAD;
> +	ref->percpu_count_ptr |= __PERCPU_REF_DEAD;
>  	ref->confirm_kill = confirm_kill;
>  
>  	call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
> @@ -166,24 +168,24 @@ EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
>   */
>  void percpu_ref_reinit(struct percpu_ref *ref)
>  {
> -	unsigned long __percpu *pcpu_count = pcpu_count_ptr(ref);
> +	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
>  	int cpu;
>  
> -	BUG_ON(!pcpu_count);
> +	BUG_ON(!percpu_count);
>  	WARN_ON_ONCE(!percpu_ref_is_zero(ref));
>  
> -	atomic_long_set(&ref->count, 1 + PCPU_COUNT_BIAS);
> +	atomic_long_set(&ref->count, 1 + PERCPU_COUNT_BIAS);
>  
>  	/*
>  	 * Restore per-cpu operation.  smp_store_release() is paired with
> -	 * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees
> -	 * that the zeroing is visible to all percpu accesses which can see
> -	 * the following PCPU_REF_DEAD clearing.
> +	 * smp_read_barrier_depends() in __percpu_ref_alive() and
> +	 * guarantees that the zeroing is visible to all percpu accesses
> +	 * which can see the following __PERCPU_REF_DEAD clearing.
>  	 */
>  	for_each_possible_cpu(cpu)
> -		*per_cpu_ptr(pcpu_count, cpu) = 0;
> +		*per_cpu_ptr(percpu_count, cpu) = 0;
>  
> -	smp_store_release(&ref->pcpu_count_ptr,
> -			  ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
> +	smp_store_release(&ref->percpu_count_ptr,
> +			  ref->percpu_count_ptr & ~__PERCPU_REF_DEAD);
>  }
>  EXPORT_SYMBOL_GPL(percpu_ref_reinit);
> -- 
> 1.9.3
> 
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