[PATCH 1/2] ubifs: drop softlimit and delta fields from struct ubifs_wbuf

[Boris Brezillon]

On Wed, 14 Sep 2016 12:24:34 +0200
Rafał Miłecki <zajec5 at gmail.com> wrote:

> From: Rafał Miłecki <rafal at milecki.pl>
> 
> Values of these fields are set during init and never modified. They are
> used (read) in a single function only. There isn't really any reason to
> keep them in a struct. It only makes struct just a bit bigger without
> any clear gain.
> 
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> ---
>  fs/ubifs/io.c    | 18 ++++++++++--------
>  fs/ubifs/ubifs.h |  5 -----
>  2 files changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
> index 97be412..4d6ce4a 100644
> --- a/fs/ubifs/io.c
> +++ b/fs/ubifs/io.c
> @@ -452,16 +452,22 @@ static enum hrtimer_restart wbuf_timer_callback_nolock(struct hrtimer *timer)
>   */
>  static void new_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
>  {
> +	ktime_t softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
> +	unsigned long long delta;
> +
> +	delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
> +	delta *= 1000000000ULL;
> +
>  	ubifs_assert(!hrtimer_active(&wbuf->timer));
> +	ubifs_assert(delta <= ULONG_MAX);

Hm, do we really want to recalculate delta each time we reschedule the
wbuf timer?

How about making the softlimit and delta variables static and
initializing them once?

>  
>  	if (wbuf->no_timer)
>  		return;
>  	dbg_io("set timer for jhead %s, %llu-%llu millisecs",
>  	       dbg_jhead(wbuf->jhead),
> -	       div_u64(ktime_to_ns(wbuf->softlimit), USEC_PER_SEC),
> -	       div_u64(ktime_to_ns(wbuf->softlimit) + wbuf->delta,
> -		       USEC_PER_SEC));
> -	hrtimer_start_range_ns(&wbuf->timer, wbuf->softlimit, wbuf->delta,
> +	       div_u64(ktime_to_ns(softlimit), USEC_PER_SEC),
> +	       div_u64(ktime_to_ns(softlimit) + delta, USEC_PER_SEC));
> +	hrtimer_start_range_ns(&wbuf->timer, softlimit, delta,
>  			       HRTIMER_MODE_REL);
>  }
>  
> @@ -1059,10 +1065,6 @@ int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
>  
>  	hrtimer_init(&wbuf->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
>  	wbuf->timer.function = wbuf_timer_callback_nolock;
> -	wbuf->softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
> -	wbuf->delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
> -	wbuf->delta *= 1000000000ULL;
> -	ubifs_assert(wbuf->delta <= ULONG_MAX);
>  	return 0;
>  }
>  
> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
> index 4617d45..11bc8fa 100644
> --- a/fs/ubifs/ubifs.h
> +++ b/fs/ubifs/ubifs.h
> @@ -644,9 +644,6 @@ typedef int (*ubifs_lpt_scan_callback)(struct ubifs_info *c,
>   * @io_mutex: serializes write-buffer I/O
>   * @lock: serializes @buf, @lnum, @offs, @avail, @used, @next_ino and @inodes
>   *        fields
> - * @softlimit: soft write-buffer timeout interval
> - * @delta: hard and soft timeouts delta (the timer expire interval is @softlimit
> - *         and @softlimit + @delta)
>   * @timer: write-buffer timer
>   * @no_timer: non-zero if this write-buffer does not have a timer
>   * @need_sync: non-zero if the timer expired and the wbuf needs sync'ing
> @@ -675,8 +672,6 @@ struct ubifs_wbuf {
>  	int (*sync_callback)(struct ubifs_info *c, int lnum, int free, int pad);
>  	struct mutex io_mutex;
>  	spinlock_t lock;
> -	ktime_t softlimit;
> -	unsigned long long delta;
>  	struct hrtimer timer;
>  	unsigned int no_timer:1;
>  	unsigned int need_sync:1;