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Tue, 24 Feb 2026 13:57:36 -0800 (PST) Message-ID: <825ab511-9335-4827-a3fd-6dd6f498326e@kernel.dk> Date: Tue, 24 Feb 2026 14:57:35 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] buffer: fix kmemleak false positive in submit_bh_wbc To: Sasha Levin , viro@zeniv.linux.org.uk, brauner@kernel.org Cc: jack@suse.cz, changfengnan@bytedance.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260224190637.3279019-1-sashal@kernel.org> Content-Language: en-US From: Jens Axboe In-Reply-To: <20260224190637.3279019-1-sashal@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/24/26 12:06 PM, Sasha Levin wrote: > Bios allocated in submit_bh_wbc are properly freed via their end_io > handler. Since commit 48f22f80938d, bio_put() caches them in a per-CPU > bio cache for reuse rather than freeing them back to the mempool. > While cached bios are reachable by kmemleak via the per-CPU cache > pointers, once recycled for new I/O they are only referenced by block > layer internals that kmemleak does not scan, causing false positive > leak reports. > > Mark the bio allocation with kmemleak_not_leak() to suppress the false > positive. > > Fixes: 48f22f80938d ("block: enable per-cpu bio cache by default") > Assisted-by: Claude:claude-opus-4-6 > Signed-off-by: Sasha Levin > --- > fs/buffer.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 22b43642ba574..c298df6c7f8c6 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -49,6 +49,7 @@ > #include > #include > #include > +#include > #include > #include > > @@ -2799,6 +2800,7 @@ static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh, > opf |= REQ_PRIO; > > bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO); > + kmemleak_not_leak(bio); > > fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO); What if they do end up getting leaked? This seems like an odd work-around, would be better to ensure the caching side marks them as in-use when grabbed and freed when put. -- Jens Axboe