bfq-iosched: remove unused variable

bfqd->sb_shift was attempted used as a cache for the sbitmap queue
shift, but we don't need it, as it never changes. Kill it with fire.
Acked-by: NPaolo Valente <paolo.valente@linaro.org>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

@@ -5085,26 +5085,24 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
  */
 static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
 {
-	bfqd->sb_shift = bt->sb.shift;
-
 	/*
 	 * In-word depths if no bfq_queue is being weight-raised:
 	 * leaving 25% of tags only for sync reads.
 	 *
 	 * In next formulas, right-shift the value
-	 * (1U<<bfqd->sb_shift), instead of computing directly
-	 * (1U<<(bfqd->sb_shift - something)), to be robust against
-	 * any possible value of bfqd->sb_shift, without having to
+	 * (1U<<bt->sb.shift), instead of computing directly
+	 * (1U<<(bt->sb.shift - something)), to be robust against
+	 * any possible value of bt->sb.shift, without having to
 	 * limit 'something'.
 	 */
 	/* no more than 50% of tags for async I/O */
-	bfqd->word_depths[0][0] = max((1U<<bfqd->sb_shift)>>1, 1U);
+	bfqd->word_depths[0][0] = max((1U << bt->sb.shift) >> 1, 1U);
 	/*
 	 * no more than 75% of tags for sync writes (25% extra tags
 	 * w.r.t. async I/O, to prevent async I/O from starving sync
 	 * writes)
 	 */
-	bfqd->word_depths[0][1] = max(((1U<<bfqd->sb_shift) * 3)>>2, 1U);
+	bfqd->word_depths[0][1] = max(((1U << bt->sb.shift) * 3) >> 2, 1U);
 
 	/*
 	 * In-word depths in case some bfq_queue is being weight-
@@ -5114,9 +5112,9 @@ static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
 	 * shortage.
 	 */
 	/* no more than ~18% of tags for async I/O */
-	bfqd->word_depths[1][0] = max(((1U<<bfqd->sb_shift) * 3)>>4, 1U);
+	bfqd->word_depths[1][0] = max(((1U << bt->sb.shift) * 3) >> 4, 1U);
 	/* no more than ~37% of tags for sync writes (~20% extra tags) */
-	bfqd->word_depths[1][1] = max(((1U<<bfqd->sb_shift) * 6)>>4, 1U);
+	bfqd->word_depths[1][1] = max(((1U << bt->sb.shift) * 6) >> 4, 1U);
 }
 
 static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)

block/bfq-iosched.h

@@ -635,12 +635,6 @@ struct bfq_data {
 	/* bfqq associated with the task issuing current bio for merging */
 	struct bfq_queue *bio_bfqq;
 
-	/*
-	 * Cached sbitmap shift, used to compute depth limits in
-	 * bfq_update_depths.
-	 */
-	unsigned int sb_shift;
-
 	/*
 	 * Depth limits used in bfq_limit_depth (see comments on the
 	 * function)