rand: make randX_upto() do the end value increment

We should not do it in the caller, the functions that need
fixing are really rand32/64_upto() instead.

Also move a (now) misplaced comment.

Fixes: c6fc6d2ab2c2 ("rand: ensure that rand_between() can reach max value")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/lib/rand.h b/lib/rand.h
index 3554f6985e93ff02eacfb364054a5594007e88e5..1676cf98ed567653cded97eaf00a1beabe808b58 100644 (file)
--- a/lib/rand.h
+++ b/lib/rand.h
@@ -114,9 +114,6 @@ static inline double __rand_0_1(struct frand_state *state)
        }
 }
 
-/*
- * Generate a random value between 'start' and 'end', both inclusive
- */
 static inline uint32_t rand32_upto(struct frand_state *state, uint32_t end)
 {
        uint32_t r;
@@ -124,6 +121,7 @@ static inline uint32_t rand32_upto(struct frand_state *state, uint32_t end)
        assert(!state->use64);
 
        r = __rand32(&state->state32);
+       end++;
        return (int) ((double)end * (r / (FRAND32_MAX + 1.0)));
 }
 
@@ -134,16 +132,20 @@ static inline uint64_t rand64_upto(struct frand_state *state, uint64_t end)
        assert(state->use64);
 
        r = __rand64(&state->state64);
+       end++;
        return (uint64_t) ((double)end * (r / (FRAND64_MAX + 1.0)));
 }
 
+/*
+ * Generate a random value between 'start' and 'end', both inclusive
+ */
 static inline uint64_t rand_between(struct frand_state *state, uint64_t start,
                                    uint64_t end)
 {
        if (state->use64)
-               return start + rand64_upto(state, 1 + end - start);
+               return start + rand64_upto(state, end - start);
        else
-               return start + rand32_upto(state, 1 + end - start);
+               return start + rand32_upto(state, end - start);
 }
 
 extern void init_rand(struct frand_state *, bool);