On 2020/1/27 2:17 下午, Dan Carpenter wrote:
> Hello Coly Li,
>
> The patch 2aa8c529387c: "bcache: avoid unnecessary btree nodes
> flushing in btree_flush_write()" from Jan 24, 2020, leads to the
> following static checker warning:
>
> drivers/md/bcache/journal.c:444 btree_flush_write()
> warn: 'ref_nr' unsigned <= 0
>
Hi Dan,
Thank you, I will submit the fix in following v5.6-rc version.
BTW, now I use 0-DAY kernel test infrastructure from Intel and my local
gcc -Wall to detect static issue. What is the tool you use to find such
check-minus-value-to-unsigned prlbem ?
Coly Li
> drivers/md/bcache/journal.c
> 422 static void btree_flush_write(struct cache_set *c)
> 423 {
> 424 struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
> 425 unsigned int i, nr, ref_nr;
> ^^^^^^
>
> 426 atomic_t *fifo_front_p, *now_fifo_front_p;
> 427 size_t mask;
> 428
> 429 if (c->journal.btree_flushing)
> 430 return;
> 431
> 432 spin_lock(&c->journal.flush_write_lock);
> 433 if (c->journal.btree_flushing) {
> 434 spin_unlock(&c->journal.flush_write_lock);
> 435 return;
> 436 }
> 437 c->journal.btree_flushing = true;
> 438 spin_unlock(&c->journal.flush_write_lock);
> 439
> 440 /* get the oldest journal entry and check its refcount */
> 441 spin_lock(&c->journal.lock);
> 442 fifo_front_p = &fifo_front(&c->journal.pin);
> 443 ref_nr = atomic_read(fifo_front_p);
> 444 if (ref_nr <= 0) {
> ^^^^^^^^^^^
> Unsigned can't be less than zero.
>
> 445 /*
> 446 * do nothing if no btree node references
> 447 * the oldest journal entry
> 448 */
> 449 spin_unlock(&c->journal.lock);
> 450 goto out;
> 451 }
> 452 spin_unlock(&c->journal.lock);
>
> regards,
> dan carpenter
>
