diff options
| -rw-r--r-- | fs/bcachefs/extents.c | 2 | ||||
| -rw-r--r-- | fs/bcachefs/util.c | 23 | ||||
| -rw-r--r-- | fs/bcachefs/util.h | 2 |
3 files changed, 16 insertions, 11 deletions
diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c index 05d5f71a7ca9..2d8042f853dc 100644 --- a/fs/bcachefs/extents.c +++ b/fs/bcachefs/extents.c @@ -99,7 +99,7 @@ static inline bool ptr_better(struct bch_fs *c, /* Pick at random, biased in favor of the faster device: */ - return bch2_rand_range(l1 + l2) > l1; + return bch2_get_random_u64_below(l1 + l2) > l1; } if (bch2_force_reconstruct_read) diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c index e0a876cbaa6b..8e3ab4bf79a9 100644 --- a/fs/bcachefs/util.c +++ b/fs/bcachefs/util.c @@ -653,19 +653,24 @@ int bch2_bio_alloc_pages(struct bio *bio, size_t size, gfp_t gfp_mask) return 0; } -size_t bch2_rand_range(size_t max) +u64 bch2_get_random_u64_below(u64 ceil) { - size_t rand; + if (ceil <= U32_MAX) + return __get_random_u32_below(ceil); - if (!max) - return 0; + /* this is the same (clever) algorithm as in __get_random_u32_below() */ + u64 rand = get_random_u64(); + u64 mult = ceil * rand; - do { - rand = get_random_long(); - rand &= roundup_pow_of_two(max) - 1; - } while (rand >= max); + if (unlikely(mult < ceil)) { + u64 bound = -ceil % ceil; + while (unlikely(mult < bound)) { + rand = get_random_u64(); + mult = ceil * rand; + } + } - return rand; + return mul_u64_u64_shr(ceil, rand, 64); } void memcpy_to_bio(struct bio *dst, struct bvec_iter dst_iter, const void *src) diff --git a/fs/bcachefs/util.h b/fs/bcachefs/util.h index e7c3541b38f3..f4a4783219d9 100644 --- a/fs/bcachefs/util.h +++ b/fs/bcachefs/util.h @@ -401,7 +401,7 @@ do { \ _ret; \ }) -size_t bch2_rand_range(size_t); +u64 bch2_get_random_u64_below(u64); void memcpy_to_bio(struct bio *, struct bvec_iter, const void *); void memcpy_from_bio(void *, struct bio *, struct bvec_iter); |