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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Johannes Weiner , Song Liu , Rik van Riel , Hugh Dickins , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Jason Gunthorpe , Kevin Tian , "Joerg Roedel (AMD)" , Robin Murphy , Steve Sistare , John Hubbard Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, iommu@lists.linux.dev, "David Hildenbrand (Arm)" , Chris Mason , stable@vger.kernel.org X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2738; i=david@kernel.org; h=from:subject:message-id; bh=MIAUtxrNu7UMyrPfJ9US1972uvFhMmrdah8Cfagy62k=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLeNFiq3/mjLcK9MvXw3uXbsj6veW5f4bigbqJ15pvXZ 8PfzbY36ChlYRDjYJAVU2QJCr5v8PLlutpqNz5mmDmsTCBDGLg4BWAi6zcwMry2UqzpjmZuylT/ eeLMYuYd3u2qtYsWsJuvPMy68MCnoAagiuD10075KxZt8v7A+kxYMkBt1qGF6xXVD+26n75zafd iFgA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Stat-Signature: 4a5zb597mosgktdmpsmnzbrc8uiny31d X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C0A2A20013 X-HE-Tag: 1793884259-459651 X-HE-Meta: U2FsdGVkX1+56YGidrPGSyZfTyBznoX+5Ou11uPQPws3OyvajaLXKpJW2awX0bKUFyhjzlXP193op4QkS6zdVez3JO8kYdwPioTDnzoKf5TbmZnyXgn4wlUtn9nRk58VyV5GDYNC934WzHaiLnkFK+A3CvGDv1+KMZqmSteJKn6COy2lOdzN605aO5gFpudCNf9MgI8uhCuKVevSPjQkv6AnZ4HdyOePl5MroTBLQ0WP8aWVB+DR1kVj1c+NwroBNVLV5ieA+ATC8Btmzy+hZZxjx9GEP7lEzXOOQYAlQSdVW7sVy9ccGmPz263HdZlALmLdQo+RqRh9P/5jFQp1JHtIXymCJGI9Qu7mDI2MNxZX1E9S0i1xK4HJY/Jz1Byqu8BvLQPElg+juWW1NcJWgggPnSkjs8yLcIzdsXAjzacb/7pdCTye4kK4b6JAyafkl2orU+0RArwSuoH74j+YYxspoyKrViXXtUopKZgUKkOb/hL/o9lzWMPn9536l7XDFCcMMDbYdI07V5asJY1xDHgAvssd2lIPk7y8NO/k0hVwPCK6t3pdVDn5RTW5ldIbUS3xy6hFA60so3/TWKlsRQfUB1W/VJWufeKdnrw+7z8NqJ8/Ts8crtSgBKv0zUeIOMg2YwbPROi4ztDvMcHLf7vxGmTjZBd9MFLwfo6B4egE7Bm9B5cuvoOkDRqDUuLYeVvO4MFWS98HRz3sf377hf/i9g/eJF537VqxppueG9FRX6FBH9hX7JydR/nmv1HHMAqDZMZOYgZPP86jmiaxoIe6WyT8+jMCl+nowJ+4ByG6uewKG+OPuV2G8Rz9OA40Ao3lAshMs9VN2leZjRtXwC4+hTVRt4jK9b6p4sAn772v+9y50dkhj5buNRcizpAnhG7ELZfjybEdZgvalusLN8fdOSXXldcsQx+nOFlXQVuotstB4PFMVCN49edKoZZYjZvzquduae2/t9Z8PZD fnp9ff0o 2vVBEOvkodr4+67qwOWTw20R1Ql2inGUurBNcpCx3njfmJK1wFcnwyM1nqkxqtrDdPberppthZweYMoVT6/A1BI3uvAXy9WyW2m8ntnzcYKWovZGUo2nea1sf3uvLey5z/epQIhbZmIJICI0MV9kUPbyUUSPDWklHphAN27bnfwecwl9cGXMI2xCSsyuNjrW/0gTLsxl9vsnqwEOR0jEXaUjgR79nRdlPkWP8QTioklwnE72Q2T3DA25SR1v79ErsZ3wwKeQ06R0Jt++2MDlQB8hSNUl/WrYdogm9LBZj+eT9oFXzc7rLahOQuA5PTmuzUETevNVoPLA6Nwk2Bii6OaWFBy1M3tT6J96nk3B0XBBb1WjpHS0LYPP0yA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 When a task zaps mappings (e.g., MADV_DONTNEED), it can drop the PT lock and defer dropping the folio references. In the meantime, page faults can refault pagecache folios, creating more references for the same folios. Let's just request a flush after enqueueing a pagecache folio whose refcount reached a certain threshold. Start flushing well before new references are refused, regardless of the caller's privileges. This is a temporary measure until we have something better. Reported-by: Chris Mason Fixes: 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP") Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand (Arm) --- include/linux/mm.h | 1 + mm/memory.c | 4 ++-- mm/mmu_gather.c | 5 +++++ 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index a82cfbce18215..87f7646a7f3ba 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2232,6 +2232,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf); /* Leave separate reserves for administrators and concurrent reference gains. */ #define FOLIO_REF_COUNT_LIMIT (INT_MAX - (1U << 26)) #define FOLIO_REF_COUNT_ADMIN_LIMIT (INT_MAX - (1U << 25)) +#define FOLIO_REF_COUNT_FLUSH_LIMIT (INT_MAX - (1U << 27)) /** * folio_ref_count_over_limit - Check whether to refuse more folio references. diff --git a/mm/memory.c b/mm/memory.c index 4800a0da14a32..d2eb313832559 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2061,8 +2061,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, pte_unmap_unlock(start_pte, ptl); /* - * If we forced a TLB flush (either due to running out of - * batch buffers or because we needed to flush dirty TLB + * If we forced a TLB flush (either to release batched + * references or because we needed to flush dirty TLB * entries before releasing the ptl), free the batched * memory too. Come back again if we didn't do everything. */ diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index 9f353f0e2ef4d..5988c42cc5144 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -190,6 +190,11 @@ static bool __tlb_remove_folio_pages_size(struct mmu_gather *tlb, batch->encoded_pages[batch->nr++] = encode_page(page, flags); batch->encoded_pages[batch->nr++] = encode_nr_pages(nr_pages); } + /* Flush pending references well before new references are refused. */ + if (unlikely((unsigned int)folio_ref_count(page_folio(page)) >= + FOLIO_REF_COUNT_FLUSH_LIMIT)) + return true; + /* * Make sure that we can always add another "page" + "nr_pages", * requiring two entries instead of only a single one. -- 2.43.0