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Tue, 31 Mar 2026 18:34:28 +0000 (GMT) Message-ID: <81857888-b6aa-4f04-bfd7-e9365d62669d@linux.ibm.com> Date: Wed, 1 Apr 2026 00:04:26 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/sparse: fix preinited section_mem_map clobbering on failure path To: Muchun Song , Andrew Morton , David Hildenbrand Cc: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Frank van der Linden , linux-mm@kvack.org, linux-kernel@vger.kernel.org, muchun.song@linux.dev References: <20260331113724.2080833-1-songmuchun@bytedance.com> Content-Language: en-US From: Donet Tom In-Reply-To: <20260331113724.2080833-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=J6enLQnS c=1 sm=1 tr=0 ts=69cc13bb cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=968KyxNXAAAA:8 a=B2iOVZ4RgrPQK8wAUSEA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMxMDE3NiBTYWx0ZWRfX3IPT0D0Vpfvj r59Fgdk5Xh7zi+wu3KO4TsG9Uzo/Me4UlliWVQuyeNK2GzP7HYKgC8ut89bu3cCxv8WMtw9n3tr 7691sWDWd/HO6Z4PGdb9j1KPloHbxbj27I/vmjFfahFBRkETOdYqZSZFIZDj+Jv+h9x9ugaSArQ GIMzzik39Zn+LWawvJd8FADztjvrszj7Ne2iUPDGu+ueaI4qxyH27WWcWWjUkiu+U/IfLVrZzN/ f7uLTgPqBuzwzkdhygT4lj8rgc6nXs/+PA9Aev+CgvqUhQZ/PLL19n8B+jo65JnU6D5vxVa2F61 WQ7cnXmsym9rSAk6r9EZLLSbA4kWm6cdaRl89FW9HQaIaXKI2KdTLxp4A1pZfCc/XAcR8kP+Kls BrT1qM0zfYh2Yng9ubJAyBUgkIT4sWUBr8e/8sfhFJeXtixYXjA7R22e0k5U5N0HFq8jwPgVrAi ubJgZJuLoWUgHLxq6EQ== X-Proofpoint-GUID: ceGfuKj6JtU_viIudgnsZLLel_znQlh6 X-Proofpoint-ORIG-GUID: fnvtgq5ZdlXM3Kgq-hrrYo-gCMT4N89R X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-31_04,2026-03-31_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1011 adultscore=0 priorityscore=1501 bulkscore=0 phishscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603310176 X-Rspamd-Queue-Id: 1890C14000F X-Stat-Signature: 9i5p84gsup31oisb7ou7c9d8yia9g6ei X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774982085-945297 X-HE-Meta: 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 WqCwMjME t2XI1c6S9M2qbq6KOj5/gwbHavN10lE9e97L6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Muchun On 3/31/26 5:07 PM, Muchun Song wrote: > sparse_init_nid() is careful to leave alone every section whose vmemmap > has already been set up by sparse_vmemmap_init_nid_early(); it only > clears section_mem_map for the rest: > > if (!preinited_vmemmap_section(ms)) > ms->section_mem_map = 0; > > A leftover line after that conditional block > > ms->section_mem_map = 0; > > was supposed to be deleted but was missed in the failure path, causing the > field to be overwritten for all sections when memory allocation fails, > effectively destroying the pre-initialization check. > > Drop the stray assignment so that preinited sections retain their > already valid state. > > Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap section init at boot") > Signed-off-by: Muchun Song > --- > mm/sparse.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index c2eb36bfb86d..3a14b733bf71 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -584,7 +584,6 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, > ms = __nr_to_section(pnum); > if (!preinited_vmemmap_section(ms)) > ms->section_mem_map = 0; > - ms->section_mem_map = 0; This looks correct to me. I have a couple of questions: 1. As I understand, section_mem_map initially stores the nid    during early boot, and later it stores a pointer to an    array of struct page. In sparse_init_nid(), the struct page    array is stored in section_mem_map via    sparse_init_early_section(). If    __populate_section_memmap() fails, we are  clearing the nid    stored in section_mem_map right? 2. Another question: if sparse_init_nid() fails for some    sections, there is no retry mechanism to add them again,    correct? 3. when ms->section_mem_map is set to 0    for a pre-initialized section, does it only affect the    pre-initialization check, or could it lead to other issues? - Donet > } > } >