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Mon, 29 Sep 2025 06:58:04 -0400 (EDT) Date: Mon, 29 Sep 2025 11:58:01 +0100 From: Kiryl Shutsemau To: Wei Yang Cc: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, linux-mm@kvack.org, Dan Carpenter Subject: Re: [Patch v4 1/2] mm/ksm: don't call mm_slot_entry() when the slot is NULL Message-ID: References: <20250927004539.19308-1-richard.weiyang@gmail.com> <20250927004539.19308-2-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250927004539.19308-2-richard.weiyang@gmail.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7DC5C100009 X-Stat-Signature: qeg6qxsjgxsco9d8tuz33ons65hkk6pt X-Rspam-User: X-HE-Tag: 1759143487-66926 X-HE-Meta: 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 4WI8hK+8 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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: On Sat, Sep 27, 2025 at 12:45:38AM +0000, Wei Yang wrote: > When using mm_slot in ksm, there is code like: > > slot = mm_slot_lookup(mm_slots_hash, mm); > mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); > if (mm_slot && ..) { > } > > The mm_slot_entry() won't return a valid value if slot is NULL generally. > But currently it works since slot is the first element of struct > ksm_mm_slot. > > To reduce the ambiguity and make it robust, only call mm_slot_entry() > when we have a valid slot. > > Signed-off-by: Wei Yang > Cc: David Hildenbrand > Cc: Dev Jain > Cc: Lance Yang > Cc: Kiryl Shutsemau > Cc: xu xin > Cc: Dan Carpenter > Cc: Chengming Zhou Acked-by: Kiryl Shutsemau -- Kiryl Shutsemau / Kirill A. 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