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bh=lOeRWLkwojHUr+kCvKucNzS99VgHJLzpoVD7LuCzBQU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793778380; v=1; x=1794383180; b=SrUDrC1nEYDfnDbcjhM6U8YikKVcoVmMepiQ6kH0khyq+37Cz41vPf1A6NfktIbZup9kWkDF TOQXoVJizKP5XMi9kWwwoYvJDEJ9lfVjWTc4YY4geW02Jzkqf2EcMY2RbcYoGPvpwyXhG6JPIlE 5Jr2093XGM9q6FtQWqh9izns= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id ee7e5ef34284ef57; Wed, 04 Nov 2026 07:46:19 +0000 X-Mizu-Trace-ID: ee7e5ef34284ef57 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: ljs@kernel.org Cc: david@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, boqun@kernel.org, longman@redhat.com, surenb@google.com, vbabka@kernel.org, shakeel.butt@linux.dev, yonghong.song@linux.dev, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, martin.lau@linux.dev, song@kernel.org, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 1/5] Revert "mm/khugepaged: remove definition of struct khugepaged_mm_slot" Date: Wed, 4 Nov 2026 15:46:13 +0800 Message-ID: <20261104074613.30583-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261103-khugepaged-latency-fix-v1-1-a07ab16ac860@kernel.org> References: <20261103-khugepaged-latency-fix-v1-1-a07ab16ac860@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Tue, Nov 03, 2026 at 08:27:42AM +0000, Lorenzo Stoakes (ARM) wrote: >This partially reverts commit b4c9ffb54b32 ("mm/khugepaged: remove >definition of struct khugepaged_mm_slot"), as a subsequent commit needs to >resurrect this type to store additional data alongside the mm_slot. > >The stated intent of the commit was to address a NULL check in >__khugepaged_exit(): > > mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); > >slot can be NULL and mm_slot_entry() is an alias for container_of(), so >this is container_of() a NULL value. > >This was benign as there was only 1 field in khugepaged_mm_slot (offsetting >NULL at 0 results in NULL), however it was right to fix this, so retain the >fix. > >It also unwrapped KMEM_CACHE() in khugepaged_init(). This was a mistake, >and was itself reverted in commit c14bdcc9f274 ("mm/khugepaged: use >KMEM_CACHE()"). Therefore, retain the KMEM_CACHE() form in this revert. > >Signed-off-by: Lorenzo Stoakes (ARM) >--- With patch #02 adding a per-mm scan position, bringing khugepaged_mm_slot back looks reasonable to me ;) Reviewed-by: Lance Yang