[PATCH v4 03/40] lib/sbitmap; optimize __sbitmap_get_word() by using find_and_set_bit()

Yury Norov
2024-06-20T17:57:17Z

__sbitmap_get_word() opencodes either find_and_set_bit_wrap(), or
find_and_set_next_bit(), depending on wrap parameter. Simplify it
by using atomic find_bit() API.

While here, simplify sbitmap_find_bit_in_word(), which calls it.

CC: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
lib/sbitmap.c | 47 ++++++++++-------------------------------------
1 file changed, 10 insertions(+), 37 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 1e453f825c05..3881996217c9 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -4,6 +4,7 @@
* Copyright (C) 2013-2014 Jens Axboe
*/

+#include <linux/find_atomic.h>
#include <linux/sched.h>
#include <linux/random.h>
#include <linux/sbitmap.h>
@@ -133,38 +134,13 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
}
EXPORT_SYMBOL_GPL(sbitmap_resize);

-static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
+static inline int __sbitmap_get_word(unsigned long *word, unsigned long depth,
unsigned int hint, bool wrap)
{
- int nr;
-
- /* don't wrap if starting from 0 */
- wrap = wrap && hint;
-
- while (1) {
- nr = find_next_zero_bit(word, depth, hint);
- if (unlikely(nr >= depth)) {
- /*
- * We started with an offset, and we didn't reset the
- * offset to 0 in a failure case, so start from 0 to
- * exhaust the map.
- */
- if (hint && wrap) {
- hint = 0;
- continue;
- }
- return -1;
- }
+ if (wrap)
+ return find_and_set_bit_wrap_lock(word, depth, hint);

- if (!test_and_set_bit_lock(nr, word))
- break;
-
- hint = nr + 1;
- if (hint >= depth - 1)
- hint = 0;
- }
-
- return nr;
+ return find_and_set_next_bit_lock(word, depth, hint);
}

static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
@@ -175,15 +151,12 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
int nr;

do {
- nr = __sbitmap_get_word(&map->word, depth,
- alloc_hint, wrap);
- if (nr != -1)
- break;
- if (!sbitmap_deferred_clear(map))
- break;
- } while (1);
+ nr = __sbitmap_get_word(&map->word, depth, alloc_hint, wrap);
+ if (nr < depth)
+ return nr;
+ } while (sbitmap_deferred_clear(map));

- return nr;
+ return -1;
}

static int sbitmap_find_bit(struct sbitmap *sb,
--
2.43.0