On Thu, Sep 14, 2017 at 07:59:43AM -0700, Omar Sandoval wrote:
[snip]
> Honestly I prefer your original patch with a comment on depth += nr. I'd
> be happy with the following incremental patch on top of your original v4
> patch.
Oh, and the change renaming the off parameter to start would be good to
include, too.
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
> index 2329b9e1a0e2..8d747048ae4f 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -218,7 +218,7 @@ typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
>
> /**
> * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
> - * @off: Where to start the iteration
> + * @off: Where to start the iteration.
> * @sb: Bitmap to iterate over.
> * @fn: Callback. Should return true to continue or false to break early.
> * @data: Pointer to pass to callback.
> @@ -230,11 +230,16 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb,
> unsigned int off,
> sb_for_each_fn fn, void *data)
> {
> - unsigned int index = SB_NR_TO_INDEX(sb, off);
> - unsigned int nr = SB_NR_TO_BIT(sb, off);
> + unsigned int index;
> + unsigned int nr;
> unsigned int scanned = 0;
>
> - while (1) {
> + if (off >= sb->depth)
> + off = 0;
> + index = SB_NR_TO_INDEX(sb, off);
> + nr = SB_NR_TO_BIT(sb, off);
> +
> + while (scanned < sb->depth) {
> struct sbitmap_word *word = &sb->map[index];
> unsigned int depth = min_t(unsigned int, word->depth - nr,
> sb->depth - scanned);
> @@ -243,6 +248,11 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb,
> if (!word->word)
> goto next;
>
> + /*
> + * On the first iteration of the outer loop, we need to add the
> + * bit offset back to the size of the word for find_next_bit().
> + * On all other iterations, nr is zero, so this is a noop.
> + */
> depth += nr;
> off = index << sb->shift;
> while (1) {
> @@ -254,9 +264,7 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb,
>
> nr++;
> }
> - next:
> - if (scanned >= sb->depth)
> - break;
> +next:
> nr = 0;
> if (++index >= sb->map_nr)
> index = 0;
> @@ -268,9 +276,6 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb,
> * @sb: Bitmap to iterate over.
> * @fn: Callback. Should return true to continue or false to break early.
> * @data: Pointer to pass to callback.
> - *
> - * This is inline even though it's non-trivial so that the function calls to the
> - * callback will hopefully get optimized away.
> */
> static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
> void *data)
