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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1760450944; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=HTt/KzKieiee5hMQF+Yl+hZuVbxPhLlk+WHV6D9guo8=; b=qmHUBqwKWNT5vYFudzOiUF4zcASTLZYuSKIEBYKIYVECM3evlnYbwtVC8+wujvSBGhkRvY OyuizPA56TwSUlr7qmo4GZLrjp3R+5oetCgXTIS7kckygImIJsFsBocWRNnvc2skNg4ZEq Ug6JIGrNsyZQALcEojvwDxh6J+Z7bGw= From: Hao Ge To: Vlastimil Babka , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Shakeel Butt , Michal Hocko , Roman Gushchin , Muchun Song , Suren Baghdasaryan Cc: Harry Yoo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Subject: [PATCH v2] slab: Add check for memcg_data's upper bits in folio_memcg_kmem Date: Tue, 14 Oct 2025 22:08:15 +0800 Message-Id: <20251014140815.383823-1-hao.ge@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 967CE40014 X-Stat-Signature: 3z9mdbxn78jfb1oomm7iukb13xjqejtc X-Rspam-User: X-HE-Tag: 1760450946-863046 X-HE-Meta: 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 iE0dyPoE z420EWf1JXfpJyqwN+MTZnW5HQtTs04890mRaL2oJiFwomzS0B+ay0WT3WWrSR5AkfFQ27JmTprggXgC2hjJVkjWfJOq6F2r50/kJhyCx2S69mNsH7regMjzoulwWWL2L2QOdw3BMO/2EJsNO07jmt8xBl1nHTpdxc1IN9aXyRyWNk//Au4JJ1bn8fnA6cPD+/l2q0BTnDfEaTOVRpjdQKzU95842Na8qoOhH0m7T6Du1aIQDklzyX5lyM2uQ/e8nNenC/KfIaAg92gKdQwgFXiskdQ== 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: From: Hao Ge This is because OBJEXTS_ALLOC_FAIL and OBJEXTS_ALLOC_FAIL currently share the same bit position. Therefore, we cannot simply determine whether memcg_data still points to the slabobj_ext vector by checking folio->memcg_data & MEMCG_DATA_OBJEXTS. We can distinguish between these two cases by checking whether the upper bits set: 1) MEMCG_DATA_OBJEXTS is set, but upper bits are not set, so it should mean obj_exts allocation failed (OBJEXTS_ALLOC_FAIL), thus do not report error, or 2) MEMCG_DATA_OBJEXTS is set, and upper bits are also set, so someone did not clear a valid folio->memcg_data before freeing the folio (report error). So let's add check for memcg_data's upper bits in folio_memcg_kmem. Fixes: 7612833192d5 ("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") Signed-off-by: Hao Ge --- v2: Per Vlastimil and Harry's suggestion, instead of introducing a new bit, implement this by checking if the highest bit is set. Many thanks to Vlastimil and Harry. --- include/linux/memcontrol.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 873e510d6f8d..f9f7ba14be04 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -534,7 +534,9 @@ static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *ob static inline bool folio_memcg_kmem(struct folio *folio) { VM_BUG_ON_PGFLAGS(PageTail(&folio->page), &folio->page); - VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS, folio); + VM_BUG_ON_FOLIO((folio->memcg_data & MEMCG_DATA_OBJEXTS) && + (folio->memcg_data & ~(ULONG_MAX >> 1)), + folio); return folio->memcg_data & MEMCG_DATA_KMEM; } -- 2.25.1