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Wed, 11 Jun 2025 03:47:55 -0700 (PDT) Received: from Barrys-MBP.hub ([118.92.145.159]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-313b200a23esm1020087a91.18.2025.06.11.03.47.50 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 11 Jun 2025 03:47:55 -0700 (PDT) From: Barry Song <21cnbao@gmail.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Suren Baghdasaryan , Lokesh Gidra , Mike Rapoport , Michal Hocko , Tangquan Zheng , Qi Zheng Subject: [PATCH v2] mm: madvise: use per_vma lock for MADV_FREE Date: Wed, 11 Jun 2025 22:47:45 +1200 Message-Id: <20250611104745.57405-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: DE18E40007 X-Stat-Signature: spf8aoz9gjj15hfgou8ksm66pe8sytkj X-Rspamd-Server: rspam04 X-HE-Tag: 1749638876-196306 X-HE-Meta: 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 1+LRr8Bi 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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: From: Barry Song MADV_FREE is another option, besides MADV_DONTNEED, for dynamic memory freeing in user-space native or Java heap memory management. For example, jemalloc can be configured to use MADV_FREE, and recent versions of the Android Java heap have also increasingly adopted MADV_FREE. Supporting per-VMA locking for MADV_FREE thus appears increasingly necessary. We have replaced walk_page_range() with walk_page_range_vma(). Along with the proposed madvise_lock_mode by Lorenzo, the necessary infrastructure is now in place to begin exploring per-VMA locking support for MADV_FREE and potentially other madvise using walk_page_range_vma(). This patch adds support for the PGWALK_VMA_RDLOCK walk_lock mode in walk_page_range_vma(), and leverages madvise_lock_mode from madv_behavior to select the appropriate walk_lock—either mmap_lock or per-VMA lock—based on the context. Because we now dynamically update the walk_ops->walk_lock field, we must ensure this is thread-safe. The madvise_free_walk_ops is now defined as a stack variable instead of a global constant. Acked-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Cc: "Liam R. Howlett" Cc: Vlastimil Babka Cc: Jann Horn Cc: Suren Baghdasaryan Cc: Lokesh Gidra Cc: Mike Rapoport Cc: Michal Hocko Cc: Tangquan Zheng Cc: Qi Zheng Signed-off-by: Barry Song --- -v2: * Collect David's acked-by and Lorenzo's reviewed-by; * refine changelog and code cleanup according to David and Lorenzo include/linux/pagewalk.h | 2 ++ mm/madvise.c | 25 +++++++++++++++++++------ mm/pagewalk.c | 5 ++++- 3 files changed, 25 insertions(+), 7 deletions(-) diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h index 9700a29f8afb..a4afa64ef0ab 100644 --- a/include/linux/pagewalk.h +++ b/include/linux/pagewalk.h @@ -14,6 +14,8 @@ enum page_walk_lock { PGWALK_WRLOCK = 1, /* vma is expected to be already write-locked during the walk */ PGWALK_WRLOCK_VERIFY = 2, + /* vma is expected to be already read-locked during the walk */ + PGWALK_VMA_RDLOCK_VERIFY = 3, }; /** diff --git a/mm/madvise.c b/mm/madvise.c index 790c238d04d4..267d8e4adf31 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -777,10 +777,19 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, return 0; } -static const struct mm_walk_ops madvise_free_walk_ops = { - .pmd_entry = madvise_free_pte_range, - .walk_lock = PGWALK_RDLOCK, -}; +static inline enum page_walk_lock get_walk_lock(enum madvise_lock_mode mode) +{ + switch (mode) { + case MADVISE_VMA_READ_LOCK: + return PGWALK_VMA_RDLOCK_VERIFY; + case MADVISE_MMAP_READ_LOCK: + return PGWALK_RDLOCK; + default: + /* Other modes don't require fixing up the walk_lock */ + WARN_ON_ONCE(1); + return PGWALK_RDLOCK; + } +} static int madvise_free_single_vma(struct madvise_behavior *madv_behavior, struct vm_area_struct *vma, @@ -789,6 +798,9 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior, struct mm_struct *mm = vma->vm_mm; struct mmu_notifier_range range; struct mmu_gather *tlb = madv_behavior->tlb; + struct mm_walk_ops walk_ops = { + .pmd_entry = madvise_free_pte_range, + }; /* MADV_FREE works for only anon vma at the moment */ if (!vma_is_anonymous(vma)) @@ -808,8 +820,9 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior, mmu_notifier_invalidate_range_start(&range); tlb_start_vma(tlb, vma); + walk_ops.walk_lock = get_walk_lock(madv_behavior->lock_mode); walk_page_range_vma(vma, range.start, range.end, - &madvise_free_walk_ops, tlb); + &walk_ops, tlb); tlb_end_vma(tlb, vma); mmu_notifier_invalidate_range_end(&range); return 0; @@ -1655,7 +1668,6 @@ static enum madvise_lock_mode get_lock_mode(struct madvise_behavior *madv_behavi case MADV_WILLNEED: case MADV_COLD: case MADV_PAGEOUT: - case MADV_FREE: case MADV_POPULATE_READ: case MADV_POPULATE_WRITE: case MADV_COLLAPSE: @@ -1664,6 +1676,7 @@ static enum madvise_lock_mode get_lock_mode(struct madvise_behavior *madv_behavi return MADVISE_MMAP_READ_LOCK; case MADV_DONTNEED: case MADV_DONTNEED_LOCKED: + case MADV_FREE: return MADVISE_VMA_READ_LOCK; default: return MADVISE_MMAP_WRITE_LOCK; diff --git a/mm/pagewalk.c b/mm/pagewalk.c index e478777c86e1..74f623159f7b 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -422,7 +422,7 @@ static inline void process_mm_walk_lock(struct mm_struct *mm, { if (walk_lock == PGWALK_RDLOCK) mmap_assert_locked(mm); - else + else if (walk_lock != PGWALK_VMA_RDLOCK_VERIFY) mmap_assert_write_locked(mm); } @@ -437,6 +437,9 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma, case PGWALK_WRLOCK_VERIFY: vma_assert_write_locked(vma); break; + case PGWALK_VMA_RDLOCK_VERIFY: + vma_assert_locked(vma); + break; case PGWALK_RDLOCK: /* PGWALK_RDLOCK is handled by process_mm_walk_lock */ break; -- 2.39.3 (Apple Git-146)