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Tue, 03 Feb 2026 19:40:39 -0800 (PST) From: Altan Hacigumus To: akpm@linux-foundation.org, david@fromorbit.com Cc: ahacigu.linux@gmail.com, zhengqi.arch@bytedance.com, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] mm/shrinker: Fix refcount leak in shrink_slab_memcg() Date: Tue, 3 Feb 2026 19:35:53 -0800 Message-ID: <20260204033553.50039-1-ahacigu.linux@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260203073757.135088-1-ahacigu.linux@gmail.com> References: <20260203073757.135088-1-ahacigu.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When kmem is disabled for memcg, slab-backed shrinkers are skipped. However, shrink_slab_memcg() doesn't drop the reference acquired via shrinker_try_get() before continuing. Add the missing shrinker_put(). Also, since memcg_kmem_online() and shrinker flags cannot change dynamically, remove the shrinker from the bitmap to avoid unnecessary future scans. Fixes: 50d09da8e119 ("mm: shrinker: make memcg slab shrink lockless") Suggested-by: Qi Zheng Acked-by: Qi Zheng Link: https://lore.kernel.org/r/20260203073757.135088-1-ahacigu.linux@gmail= .com Signed-off-by: Altan Hacigumus Reviewed-by: Muchun Song --- Changes in v2: - Use clear_bit() to remove shrinker from bitmap instead of just skipping --- mm/shrinker.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/shrinker.c b/mm/shrinker.c index 4a93fd433689..68dc7b4242f2 100644 --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -544,8 +544,11 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask,= int nid, =20 /* Call non-slab shrinkers even though kmem is disabled */ if (!memcg_kmem_online() && - !(shrinker->flags & SHRINKER_NONSLAB)) + !(shrinker->flags & SHRINKER_NONSLAB)) { + clear_bit(offset, unit->map); + shrinker_put(shrinker); continue; + } =20 ret =3D do_shrink_slab(&sc, shrinker, priority); if (ret =3D=3D SHRINK_EMPTY) { --=20 2.43.0