Re: [PATCH 4/7] random: remove unused reserved argument
From: Jason A. Donenfeld
Date: Sun Jan 16 2022 - 11:22:46 EST
On Sun, Jan 16, 2022 at 2:45 PM Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> wrote:
> > @@ -1342,7 +1341,7 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
> > /* never pull more than available */
> > have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
> >
> > - if ((have_bytes -= reserved) < 0)
> > + if (have_bytes < 0)
> > have_bytes = 0;
> > ibytes = min_t(size_t, ibytes, have_bytes);
>
> Hmm. We already WARN_ON(entropy_count < 0) a few lines below. Maybe move
> that assertion before the assignement of have_bytes? Then, have_bytes can
> never be lower than zero, and the code becomes even simpler. What do you
> think?
Can you send a separate patch for this that we can apply on top? It
seems reasonable anyhow. Something like:
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 327086b35797..419156d2146d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1329,7 +1329,7 @@ EXPORT_SYMBOL_GPL(add_disk_randomness);
*/
static size_t account(struct entropy_store *r, size_t nbytes, int min)
{
- int entropy_count, orig, have_bytes;
+ int entropy_count, orig;
size_t ibytes, nfrac;
BUG_ON(r->entropy_count > POOL_FRACBITS);
@@ -1337,21 +1337,17 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min)
/* Can we pull enough? */
retry:
entropy_count = orig = READ_ONCE(r->entropy_count);
- ibytes = nbytes;
- /* never pull more than available */
- have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
-
- if (have_bytes < 0)
- have_bytes = 0;
- ibytes = min_t(size_t, ibytes, have_bytes);
- if (ibytes < min)
- ibytes = 0;
-
if (WARN_ON(entropy_count < 0)) {
pr_warn("negative entropy count: pool %s count %d\n",
r->name, entropy_count);
entropy_count = 0;
}
+
+ /* never pull more than available */
+ ibytes = min_t(size_t, nbytes, entropy_count >> (ENTROPY_SHIFT + 3));
+ if (ibytes < min)
+ ibytes = 0;
+
nfrac = ibytes << (ENTROPY_SHIFT + 3);
if ((size_t) entropy_count > nfrac)
entropy_count -= nfrac;