Hello Pavel Begunkov,
The patch 13a184e26965: "block/bio: add pcpu caching for non-polling
bio_put" from Oct 21, 2022, leads to the following Smatch static
checker warning:
block/bio.c:450 bio_alloc_percpu_cache()
error: we previously assumed 'bio' could be null (see line 449)
block/bio.c
433 static struct bio *bio_alloc_percpu_cache(struct block_device *bdev,
434 unsigned short nr_vecs, blk_opf_t opf, gfp_t gfp,
435 struct bio_set *bs)
436 {
437 struct bio_alloc_cache *cache;
438 struct bio *bio;
439
440 cache = per_cpu_ptr(bs->cache, get_cpu());
441 if (!cache->free_list &&
442 READ_ONCE(cache->nr_irq) >= ALLOC_CACHE_THRESHOLD) {
Imagine "cache->free_list" is NULL but cache->nr_irq is less than the
threshold.
443 bio_alloc_irq_cache_splice(cache);
444 if (!cache->free_list) {
445 put_cpu();
446 return NULL;
447 }
448 }
449 bio = cache->free_list;
--> 450 cache->free_list = bio->bi_next;
^^^^^^^^^^^^
It would lead to a NULL dereference here.
451 cache->nr--;
452 put_cpu();
453
454 bio_init(bio, bdev, nr_vecs ? bio->bi_inline_vecs : NULL, nr_vecs, opf);
455 bio->bi_pool = bs;
456 return bio;
457 }
regards,
dan carpenter
