Commit 2d13b1ea authored by Ming Lei's avatar Ming Lei Committed by Martin K. Petersen
Browse files

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: default avatarSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent cbb9950b

include/linux/sbitmap.h

+18 −0
Original line number Diff line number Diff line
@@ -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.

lib/sbitmap.c

+3 −13
Original line number Diff line number Diff line
@@ -87,19 +87,9 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, 
	unsigned int bits_per_word;

	unsigned int i;



	if (shift < 0) {

		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--;

		}

	}

	if (shift < 0)

		shift = sbitmap_calculate_shift(depth);



	bits_per_word = 1U << shift;

	if (bits_per_word > BITS_PER_LONG)

		return -EINVAL;