diff options
| author | Ming Lei <ming.lei@redhat.com> | 2021-01-22 10:33:10 +0800 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2021-03-04 17:36:59 -0500 |
| commit | 2d13b1ea9f4affdaa7af0e0e4a1358d28f80c54f (patch) | |
| tree | 696d93ba7b70a2c7b7e631e1e9ac5d500c5f95c4 /include/linux/sbitmap.h | |
| parent | cbb9950b41dd9dfb7c2be3429ba09f83b8b1ff98 (diff) | |
scsi: sbitmap: Add sbitmap_calculate_shift() helper
Move code for calculating default shift into a public helper which can be
used by SCSI.
Link: https://lore.kernel.org/r/20210122023317.687987-7-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'include/linux/sbitmap.h')
| -rw-r--r-- | include/linux/sbitmap.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index c65ba887dcc3..3087e1f15fdd 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -332,6 +332,24 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); } +static inline int sbitmap_calculate_shift(unsigned int depth) +{ + int shift = ilog2(BITS_PER_LONG); + + /* + * If the bitmap is small, shrink the number of bits per word so + * we spread over a few cachelines, at least. If less than 4 + * bits, just forget about it, it's not going to work optimally + * anyway. + */ + if (depth >= 4) { + while ((4U << shift) > depth) + shift--; + } + + return shift; +} + /** * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file. * @sb: Bitmap to show. |