Re: [PATCH] bio: fix kmemleak false positives from percpu bio alloc cache

[Jens Axboe <axboe@kernel.dk>]

On 3/24/26 3:00 AM, Ming Lei wrote:
> When a bio is allocated from the mempool with REQ_ALLOC_CACHE set and
> later completed, bio_put() places it into the per-cpu bio_alloc_cache
> via bio_put_percpu_cache() instead of freeing it back to the
> mempool/slab. The slab allocation remains tracked by kmemleak, but the
> only reference to the bio is through the percpu cache's free_list,
> which kmemleak fails to trace through percpu memory. This causes
> kmemleak to report the cached bios as unreferenced objects.
> 
> Use symmetric kmemleak_free()/kmemleak_alloc() calls to properly track
> bios across percpu cache transitions:
> 
>  - bio_put_percpu_cache: call kmemleak_free() when a bio enters the
>    cache, unregistering it from kmemleak tracking.
> 
>  - bio_alloc_percpu_cache: call kmemleak_alloc() when a bio is taken
>    from the cache for reuse, re-registering it so that genuine leaks
>    of reused bios remain detectable.
> 
>  - __bio_alloc_cache_prune: call kmemleak_alloc() before bio_free() so
>    that kmem_cache_free()'s internal kmemleak_free() has a matching
>    allocation to pair with.

Looks fine to me, but can you please do it against for-7.1/block
instead? It's not a huge issue, and I'd rather not introduce a merge
conflict by shoving it into 7.0 if that can be avoided.

-- 
Jens Axboe