On 12/16/24 6:40 PM, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>
Currently, shallow_depth is used by bfq, kyber and mq-deadline, they both
both -> all
pass in the value for the whole sbitmap, while sbitmap treats the value
treats for -> applies to
for just one word. Which means, shallow_depth never work as expected,
work -> works
and there really is no such functional tests to covert it.
is ... tests -> is ... test or are ... tests
covert -> cover
Consider that callers doesn't know which word will be used, and it's
Consider -> Considering
doesn't -> don't
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 189140bf11fc..92e77bc13cf6 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -213,12 +213,12 @@ int sbitmap_get(struct sbitmap *sb);
* sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
* limiting the depth used from each word.
* @sb: Bitmap to allocate from.
- * @shallow_depth: The maximum number of bits to allocate from a single word.
+ * @shallow_depth: The maximum number of bits to allocate from the bitmap.
*
* This rather specific operation allows for having multiple users with
* different allocation limits. E.g., there can be a high-priority class that
* uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
- * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
+ * with a @shallow_depth of (sb->depth << 1). Then, the low-priority
(sb->depth << 1) -> (sb->depth >> 1)
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index d3412984170c..6b8b909614a5 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -208,8 +208,27 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
return nr;
}
+static unsigned int __map_depth_with_shallow(const struct sbitmap *sb,
+ int index,
+ unsigned int shallow_depth)
+{
+ unsigned int pre_word_bits = 0;
+
+ if (shallow_depth >= sb->depth)
+ return __map_depth(sb, index);
+
+ if (index > 0)
+ pre_word_bits += (index - 1) << sb->shift;
Why "index - 1" instead of "index"?
+
+ if (shallow_depth <= pre_word_bits)
+ return 0;
+
+ return min_t(unsigned int, __map_depth(sb, index),
+ shallow_depth - pre_word_bits);
+}
How about renaming pre_word_bits into lower_bound?
Otherwise this patch looks good to me.
Thanks,
Bart.
