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Subject[PATCH V10 3/8] sbitmap: introduce __sbitmap_for_each_set()
Date
We need to iterate ctx starting from any ctx in round robin
way, so introduce this helper.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Cc: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/sbitmap.h | 64 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 47 insertions(+), 17 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index a1904aadbc45..0dcc60e820de 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -211,10 +211,14 @@ bool sbitmap_any_bit_set(const struct sbitmap *sb);
*/
bool sbitmap_any_bit_clear(const struct sbitmap *sb);

+#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
+#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
+
typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);

/**
- * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
+ * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
+ * @start: 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.
@@ -222,35 +226,61 @@ typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
* 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)
+static inline void __sbitmap_for_each_set(struct sbitmap *sb,
+ unsigned int start,
+ sb_for_each_fn fn, void *data)
{
- unsigned int i;
+ unsigned int index;
+ unsigned int nr;
+ unsigned int scanned = 0;

- for (i = 0; i < sb->map_nr; i++) {
- struct sbitmap_word *word = &sb->map[i];
- unsigned int off, nr;
+ if (start >= sb->depth)
+ start = 0;
+ index = SB_NR_TO_INDEX(sb, start);
+ nr = SB_NR_TO_BIT(sb, start);

- if (!word->word)
- continue;
+ while (scanned < sb->depth) {
+ struct sbitmap_word *word = &sb->map[index];
+ unsigned int depth = min_t(unsigned int, word->depth - nr,
+ sb->depth - scanned);

- nr = 0;
- off = i << sb->shift;
+ scanned += depth;
+ 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;
while (1) {
- nr = find_next_bit(&word->word, word->depth, nr);
- if (nr >= word->depth)
+ nr = find_next_bit(&word->word, depth, nr);
+ if (nr >= depth)
break;
-
- if (!fn(sb, off + nr, data))
+ if (!fn(sb, (index << sb->shift) + nr, data))
return;

nr++;
}
+next:
+ nr = 0;
+ if (++index >= sb->map_nr)
+ index = 0;
}
}

-#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
-#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
+/**
+ * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
+ * @sb: Bitmap to iterate over.
+ * @fn: Callback. Should return true to continue or false to break early.
+ * @data: Pointer to pass to callback.
+ */
+static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
+ void *data)
+{
+ __sbitmap_for_each_set(sb, 0, fn, data);
+}

static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
unsigned int bitnr)
--
2.9.5
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