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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 11AC1100003 X-Stat-Signature: 64dgmhbcy4c63gu5raem3sahjgpbgdb6 X-HE-Tag: 1770176440-184064 X-HE-Meta: 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 vI3xZR1N 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- 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, /* 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; + } ret = do_shrink_slab(&sc, shrinker, priority); if (ret == SHRINK_EMPTY) { -- 2.43.0