On Mon, Nov 16, 2020 at 10:38:58AM +0100, Hannes Reinecke wrote:

On 11/16/20 10:07 AM, Ming Lei wrote:

quoted

SCSI's .device_busy will be converted to sbitmap, and sbitmap_weight
is needed, so export the helper.

Cc: Omar Sandoval <redacted>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <redacted>
Cc: Ewan D. Milne <redacted>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <redacted>
Signed-off-by: Ming Lei <redacted>
---
  include/linux/sbitmap.h |  9 +++++++++
  lib/sbitmap.c           | 11 ++++++-----
  2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 103b41c03311..34343ce3ef6c 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h

@@ -346,6 +346,15 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
   */
  void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
+
+/**
+ * sbitmap_weight() - Return how many real bits set in a &struct sbitmap.
+ * @sb: Bitmap to check.
+ *
+ * Return: How many real bits set
+ */
+unsigned int sbitmap_weight(const struct sbitmap *sb);
+
  /**
   * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
   * seq_file.

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index dcd6a89b4d2f..fb1d3c2f70a2 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c

@@ -342,20 +342,21 @@ static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
  	return weight;
  }
-static unsigned int sbitmap_weight(const struct sbitmap *sb)
+static unsigned int sbitmap_cleared(const struct sbitmap *sb)
  {
-	return __sbitmap_weight(sb, true);
+	return __sbitmap_weight(sb, false);
  }
-static unsigned int sbitmap_cleared(const struct sbitmap *sb)
+unsigned int sbitmap_weight(const struct sbitmap *sb)
  {
-	return __sbitmap_weight(sb, false);
+	return __sbitmap_weight(sb, true) - sbitmap_cleared(sb);
  }
+EXPORT_SYMBOL_GPL(sbitmap_weight);

That is extremely confusing. Why do you change the meaning of
'sbitmap_weight' from __sbitmap_weight(sb, true) to
__sbitmap_weight(sb, true) - __sbitmap_weight(sb, false)?

Because the only user of sbitmap_weight() just uses the following way:

	sbitmap_weight(sb) - sbitmap_cleared(sb)

Frankly, I think sbitmap_weight(sb) should return real busy bits.

Does this mean that the original definition was wrong?
Or does this mean that this patch implies a different meaning of
'sbitmap_weight'?

Yeah, this patch changes meaning of sbitmap_weight(), now it is
exported, and we should make it more accurate/readable from user view.


Thanks, 
Ming