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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782886272; 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=ypz/Ukr7QMyOPoCjR35C1QTtc8LxW4fOAidoNmsA6a4=; b=C1fftJtt641Ka28ho6DUwuH0eyyGnEFHd+NqUAaH2pj2z6qcrO9mrBNmFh87dBXe4pi5Bi zsqqAcrFauvovQZ+s6hW95mW1rDy3iRnn/ZfgTO1VlA7LEv6nJCNcoEooCcSGp+zOngk6v gTs+Yre4sRJGn6mejlPtCeTpMTFQg48= From: Ye Liu To: Andrew Morton , Zi Yan Cc: Ye Liu , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 0/9] mm/page_owner: misc cleanups Date: Wed, 1 Jul 2026 14:10:43 +0800 Message-ID: <20260701061101.344679-1-ye.liu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: jzxtg13gr5ufyip8miu8dbzkxq56k5ya X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7B2F640002 X-HE-Tag: 1782886275-338930 X-HE-Meta: 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 GX2Nka6K YzCZxy3ZGCyiFKlMVo6dsJK/9ctAiZUt1gQnFg24EeTIClQ1tXi45XAxTCgFIUg9ch+Zc2QMnCmVjPqydo9lG5ckKnksZZ6JD2w85dagcwAAcdLSyMwgjr5qhbuwauGZHIb2UjlciwdsTaWvtxtnOA1Y1hOvZJ0VJPeozWatoHuBX+Y/so/3Ethq7CRorv9Ns3sloDsdFy83FeMMhArWPWkWIiESCDW6q315MtF3intL1jo0d01ZZPmkffZYsG3tPyq1K22jL1O3rI04= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: v5: - Place the two patches corresponding to the Close connection, patch8 and patch9, together in this part. - Close: https://lore.kernel.org/all/20260625014708.87386-1-ye.liu@linux.dev/ - Link: https://lore.kernel.org/all/20260701012239.315262-1-ye.liu@linux.dev/ v4: - Patch 2: also update scripts/gdb/linux/page_owner.py to use MR_NEVER instead of the hardcoded -1. - https://lore.kernel.org/all/20260630015331.147174-1-ye.liu@linux.dev/ v3: - Patch 2: add MR_NEVER directly to enum migrate_reason instead of using a local MIGRATE_REASON_NONE define (Zi Yan and Vlastimil Babka). - Patch 3 (new): convert all 'int reason' parameters in the migration callchain to 'enum migrate_reason' so the type system reflects the actual semantics. - Patch 7: make threshold_fops a single line. - Link: https://lore.kernel.org/all/20260626020522.28619-1-ye.liu@linux.dev/ v2: - Add cover letter (no code changes). - Link: https://lore.kernel.org/all/20260623065234.31866-2-ye.liu@linux.dev/ This series collects a few cleanups for mm/page_owner.c that have been accumulated while reading through the file. There is no functional change -- the goal is to make the code easier to read and maintain. Patch 1 consolidates three identical PageBuddy skip blocks into a single skip_buddy_pages() helper, eliminating the duplication and keeping the lockless-read comment in one place. Patch 2 replaces the -1 magic number used for "never migrated" with a proper MR_NEVER member in enum migrate_reason, adds the corresponding "never_migrated" string in the MIGRATE_REASON trace macro, and updates the GDB page_owner script to use MR_NEVER so that lx-dump-page-owner correctly detects unmigrated pages. Patch 3 follows up by converting the remaining 'int reason' parameters throughout the migration and hugetlb callchains to 'enum migrate_reason', making the type explicit and gaining compiler checking. The 'short last_migrate_reason' struct field in page_owner is intentionally left as 'short' since it is per-page metadata where size matters. Patch 4 hoists the CONFIG_MEMCG guard out of print_page_owner_memcg()'s body so that the real implementation and the empty stub are two clearly separate definitions, the common kernel idiom. Patch 5 adds a missing \n to the count_threshold debugfs attribute format string so that cat(1) output is properly terminated. Patch 6 moves free_ts_nsec from the allocation summary line to the free section in __dump_page_owner(), grouping it with free_pid and free_tgid where it logically belongs. This also makes the dump output consistent with print_page_owner(). Patch 7 drops the redundant page_owner_ prefix from file-scoped static symbols (stack_fops, threshold_fops, etc.). Since they cannot collide across translation units, the prefix carries no information. Patch 8 clamps the PFN advance in skip_buddy_pages() at the next MAX_ORDER_NR_PAGES boundary. The lockless buddy_order_unsafe() read can return a garbage order value if the page is concurrently allocated between the PageBuddy check and the private read, potentially causing the PFN to advance past the next bounadry whose pfn_valid() check would have caught an offline memory section. In read_page_owner(), which relies solely on boundary-aligned pfn_valid() to guard pfn_to_page(), this could lead to an unmapped mem_section access. Patch 9 avoids a TOCTOU VM_BUG_ON in print_page_owner_memcg() by reusing the page->memcg_data snapshot already taken via READ_ONCE at the top of the function, instead of calling PageMemcgKmem() which re-reads folio->memcg_data and page->compound_head locklessly with VM_BUG_ON assertions. If the page is concurrently freed and reallocated as a THP tail or slab page between the initial guards and this final call, those assertions can fire on CONFIG_DEBUG_VM=y builds. Ye Liu (9): mm/page_owner: extract skip_buddy_pages() helper to unify buddy page skipping mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason mm: use enum migrate_reason instead of int for migration reason parameters mm/page_owner: hoist CONFIG_MEMCG to function level for print_page_owner_memcg() mm/page_owner: add missing newline to count_threshold format string mm/page_owner: move free_ts_nsec output to free section in __dump_page_owner() mm/page_owner: drop redundant page_owner prefix from static symbols mm/page_owner: clamp skip_buddy_pages() PFN advance at MAX_ORDER_NR_PAGES boundary mm/page_owner: use memcg_data snapshot instead of PageMemcgKmem() to avoid TOCTOU VM_BUG_ON include/linux/hugetlb.h | 9 ++- include/linux/migrate.h | 6 +- include/linux/migrate_mode.h | 1 + include/linux/page_owner.h | 7 +- include/trace/events/migrate.h | 11 +-- mm/hugetlb.c | 3 +- mm/migrate.c | 12 +-- mm/page_owner.c | 127 ++++++++++++++++++-------------- scripts/gdb/linux/page_owner.py | 4 +- 9 files changed, 102 insertions(+), 78 deletions(-) -- 2.43.0