user/sven/linux.git/include/linux/mm.h, branch v6.16.3

mm: fix the inaccurate memory statistics issue for users

2025-07-10T04:07:55Z

On some large machines with a high number of CPUs running a 64K pagesize kernel, we found that the 'RES' field is always 0 displayed by the top command for some processes, which will cause a lot of confusion for users. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 875525 root 20 0 12480 0 0 R 0.3 0.0 0:00.08 top 1 root 20 0 172800 0 0 S 0.0 0.0 0:04.52 systemd The main reason is that the batch size of the percpu counter is quite large on these machines, caching a significant percpu value, since converting mm's rss stats into percpu_counter by commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter"). Intuitively, the batch number should be optimized, but on some paths, performance may take precedence over statistical accuracy. Therefore, introducing a new interface to add the percpu statistical count and display it to users, which can remove the confusion. In addition, this change is not expected to be on a performance-critical path, so the modification should be acceptable. In addition, the 'mm->rss_stat' is updated by using add_mm_counter() and dec/inc_mm_counter(), which are all wrappers around percpu_counter_add_batch(). In percpu_counter_add_batch(), there is percpu batch caching to avoid 'fbc->lock' contention. This patch changes task_mem() and task_statm() to get the accurate mm counters under the 'fbc->lock', but this should not exacerbate kernel 'mm->rss_stat' lock contention due to the percpu batch caching of the mm counters. The following test also confirm the theoretical analysis. I run the stress-ng that stresses anon page faults in 32 threads on my 32 cores machine, while simultaneously running a script that starts 32 threads to busy-loop pread each stress-ng thread's /proc/pid/status interface. From the following data, I did not observe any obvious impact of this patch on the stress-ng tests. w/o patch: stress-ng: info: [6848] 4,399,219,085,152 CPU Cycles 67.327 B/sec stress-ng: info: [6848] 1,616,524,844,832 Instructions 24.740 B/sec (0.367 instr. per cycle) stress-ng: info: [6848] 39,529,792 Page Faults Total 0.605 M/sec stress-ng: info: [6848] 39,529,792 Page Faults Minor 0.605 M/sec w/patch: stress-ng: info: [2485] 4,462,440,381,856 CPU Cycles 68.382 B/sec stress-ng: info: [2485] 1,615,101,503,296 Instructions 24.750 B/sec (0.362 instr. per cycle) stress-ng: info: [2485] 39,439,232 Page Faults Total 0.604 M/sec stress-ng: info: [2485] 39,439,232 Page Faults Minor 0.604 M/sec On comparing a very simple app which just allocates & touches some memory against v6.1 (which doesn't have f1a7941243c1) and latest Linus tree (4c06e63b9203) I can see that on latest Linus tree the values for VmRSS, RssAnon and RssFile from /proc/self/status are all zeroes while they do report values on v6.1 and a Linus tree with this patch. Link: https://lkml.kernel.org/r/f4586b17f66f97c174f7fd1f8647374fdb53de1c.1749119050.git.baolin.wang@linux.alibaba.com Fixes: f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") Signed-off-by: Baolin Wang Reviewed-by: Aboorva Devarajan Tested-by: Aboorva Devarajan Tested-by Donet Tom Acked-by: Shakeel Butt Acked-by: SeongJae Park Acked-by: Michal Hocko Reviewed-by: Vlastimil Babka Cc: David Hildenbrand Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2025-06-01-14-06' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-06-02T23:00:26Z

Pull more MM updates from Andrew Morton: - "zram: support algorithm-specific parameters" from Sergey Senozhatsky adds infrastructure for passing algorithm-specific parameters into zram. A single parameter `winbits' is implemented at this time. - "memcg: nmi-safe kmem charging" from Shakeel Butt makes memcg charging nmi-safe, which is required by BFP, which can operate in NMI context. - "Some random fixes and cleanup to shmem" from Kemeng Shi implements small fixes and cleanups in the shmem code. - "Skip mm selftests instead when kernel features are not present" from Zi Yan fixes some issues in the MM selftest code. - "mm/damon: build-enable essential DAMON components by default" from SeongJae Park reworks DAMON Kconfig to make it easier to enable CONFIG_DAMON. - "sched/numa: add statistics of numa balance task migration" from Libo Chen adds more info into sysfs and procfs files to improve visibility into the NUMA balancer's task migration activity. - "selftests/mm: cow and gup_longterm cleanups" from Mark Brown provides various updates to some of the MM selftests to make them play better with the overall containing framework. * tag 'mm-stable-2025-06-01-14-06' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (43 commits) mm/khugepaged: clean up refcount check using folio_expected_ref_count() selftests/mm: fix test result reporting in gup_longterm selftests/mm: report unique test names for each cow test selftests/mm: add helper for logging test start and results selftests/mm: use standard ksft_finished() in cow and gup_longterm selftests/damon/_damon_sysfs: skip testcases if CONFIG_DAMON_SYSFS is disabled sched/numa: add statistics of numa balance task sched/numa: fix task swap by skipping kernel threads tools/testing: check correct variable in open_procmap() tools/testing/vma: add missing function stub mm/gup: update comment explaining why gup_fast() disables IRQs selftests/mm: two fixes for the pfnmap test mm/khugepaged: fix race with folio split/free using temporary reference mm: add CONFIG_PAGE_BLOCK_ORDER to select page block order mmu_notifiers: remove leftover stub macros selftests/mm: deduplicate test names in madv_populate kcov: rust: add flags for KCOV with Rust mm: rust: make CONFIG_MMU ifdefs more narrow mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free_pgtables() mm/damon/Kconfig: enable CONFIG_DAMON by default ...

mm: rename page->index to page->__folio_index

2025-06-01T05:46:06Z

All users of page->index have been converted to not refer to it any more. Update a few pieces of documentation that were missed and prevent new users from appearing (or at least make them easy to grep for). Link: https://lkml.kernel.org/r/20250514181508.3019795-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Acked-by: David Hildenbrand Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-05-31T22:44:16Z

Pull MM updates from Andrew Morton: - "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of creating a pte which addresses the first page in a folio and reduces the amount of plumbing which architecture must implement to provide this. - "Misc folio patches for 6.16" from Matthew Wilcox is a shower of largely unrelated folio infrastructure changes which clean things up and better prepare us for future work. - "memory,x86,acpi: hotplug memory alignment advisement" from Gregory Price adds early-init code to prevent x86 from leaving physical memory unused when physical address regions are not aligned to memory block size. - "mm/compaction: allow more aggressive proactive compaction" from Michal Clapinski provides some tuning of the (sadly, hard-coded (more sadly, not auto-tuned)) thresholds for our invokation of proactive compaction. In a simple test case, the reduction of a guest VM's memory consumption was dramatic. - "Minor cleanups and improvements to swap freeing code" from Kemeng Shi provides some code cleaups and a small efficiency improvement to this part of our swap handling code. - "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin adds the ability for a ptracer to modify syscalls arguments. At this time we can alter only "system call information that are used by strace system call tampering, namely, syscall number, syscall arguments, and syscall return value. This series should have been incorporated into mm.git's "non-MM" branch, but I goofed. - "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl against /proc/pid/pagemap. This permits CRIU to more efficiently get at the info about guard regions. - "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan implements that fix. No runtime effect is expected because validate_page_before_insert() happens to fix up this error. - "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David Hildenbrand basically brings uprobe text poking into the current decade. Remove a bunch of hand-rolled implementation in favor of using more current facilities. - "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman Khandual provides enhancements and generalizations to the pte dumping code. This might be needed when 128-bit Page Table Descriptors are enabled for ARM. - "Always call constructor for kernel page tables" from Kevin Brodsky ensures that the ctor/dtor is always called for kernel pgtables, as it already is for user pgtables. This permits the addition of more functionality such as "insert hooks to protect page tables". This change does result in various architectures performing unnecesary work, but this is fixed up where it is anticipated to occur. - "Rust support for mm_struct, vm_area_struct, and mmap" from Alice Ryhl adds plumbing to permit Rust access to core MM structures. - "fix incorrectly disallowed anonymous VMA merges" from Lorenzo Stoakes takes advantage of some VMA merging opportunities which we've been missing for 15 years. - "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from SeongJae Park optimizes process_madvise()'s TLB flushing. Instead of flushing each address range in the provided iovec, we batch the flushing across all the iovec entries. The syscall's cost was approximately halved with a microbenchmark which was designed to load this particular operation. - "Track node vacancy to reduce worst case allocation counts" from Sidhartha Kumar makes the maple tree smarter about its node preallocation. stress-ng mmap performance increased by single-digit percentages and the amount of unnecessarily preallocated memory was dramaticelly reduced. - "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes a few unnecessary things which Baoquan noted when reading the code. - ""Enhance sysfs handling for memory hotplug in weighted interleave" from Rakie Kim "enhances the weighted interleave policy in the memory management subsystem by improving sysfs handling, fixing memory leaks, and introducing dynamic sysfs updates for memory hotplug support". Fixes things on error paths which we are unlikely to hit. - "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory" from SeongJae Park introduces new DAMOS quota goal metrics which eliminate the manual tuning which is required when utilizing DAMON for memory tiering. - "mm/vmalloc.c: code cleanup and improvements" from Baoquan He provides cleanups and small efficiency improvements which Baoquan found via code inspection. - "vmscan: enforce mems_effective during demotion" from Gregory Price changes reclaim to respect cpuset.mems_effective during demotion when possible. because presently, reclaim explicitly ignores cpuset.mems_effective when demoting, which may cause the cpuset settings to violated. This is useful for isolating workloads on a multi-tenant system from certain classes of memory more consistently. - "Clean up split_huge_pmd_locked() and remove unnecessary folio pointers" from Gavin Guo provides minor cleanups and efficiency gains in in the huge page splitting and migrating code. - "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache for `struct mem_cgroup', yielding improved memory utilization. - "add max arg to swappiness in memory.reclaim and lru_gen" from Zhongkun He adds a new "max" argument to the "swappiness=" argument for memory.reclaim MGLRU's lru_gen. This directs proactive reclaim to reclaim from only anon folios rather than file-backed folios. - "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the first step on the path to permitting the kernel to maintain existing VMs while replacing the host kernel via file-based kexec. At this time only memblock's reserve_mem is preserved. - "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides and uses a smarter way of looping over a pfn range. By skipping ranges of invalid pfns. - "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning when a task is pinned a single NUMA mode. Dramatic performance benefits were seen in some real world cases. - "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank Garg addresses a warning which occurs during memory compaction when using JFS. - "move all VMA allocation, freeing and duplication logic to mm" from Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more appropriate mm/vma.c. - "mm, swap: clean up swap cache mapping helper" from Kairui Song provides code consolidation and cleanups related to the folio_index() function. - "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that. - "memcg: Fix test_memcg_min/low test failures" from Waiman Long addresses some bogus failures which are being reported by the test_memcontrol selftest. - "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo Stoakes commences the deprecation of file_operations.mmap() in favor of the new file_operations.mmap_prepare(). The latter is more restrictive and prevents drivers from messing with things in ways which, amongst other problems, may defeat VMA merging. - "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples the per-cpu memcg charge cache from the objcg's one. This is a step along the way to making memcg and objcg charging NMI-safe, which is a BPF requirement. - "mm/damon: minor fixups and improvements for code, tests, and documents" from SeongJae Park is yet another batch of miscellaneous DAMON changes. Fix and improve minor problems in code, tests and documents. - "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg stats to be irq safe. Another step along the way to making memcg charging and stats updates NMI-safe, a BPF requirement. - "Let unmap_hugepage_range() and several related functions take folio instead of page" from Fan Ni provides folio conversions in the hugetlb code. * tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits) mm: pcp: increase pcp->free_count threshold to trigger free_high mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range() mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page mm/hugetlb: pass folio instead of page to unmap_ref_private() memcg: objcg stock trylock without irq disabling memcg: no stock lock for cpu hot-unplug memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs memcg: make count_memcg_events re-entrant safe against irqs memcg: make mod_memcg_state re-entrant safe against irqs memcg: move preempt disable to callers of memcg_rstat_updated memcg: memcg_rstat_updated re-entrant safe against irqs mm: khugepaged: decouple SHMEM and file folios' collapse selftests/eventfd: correct test name and improve messages alloc_tag: check mem_profiling_support in alloc_tag_init Docs/damon: update titles and brief introductions to explain DAMOS selftests/damon/_damon_sysfs: read tried regions directories in order mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject() mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat() mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs ...

Merge tag 'net-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

2025-05-28T22:24:36Z

Pull networking updates from Paolo Abeni: "Core: - Implement the Device Memory TCP transmit path, allowing zero-copy data transmission on top of TCP from e.g. GPU memory to the wire. - Move all the IPv6 routing tables management outside the RTNL scope, under its own lock and RCU. The route control path is now 3x times faster. - Convert queue related netlink ops to instance lock, reducing again the scope of the RTNL lock. This improves the control plane scalability. - Refactor the software crc32c implementation, removing unneeded abstraction layers and improving significantly the related micro-benchmarks. - Optimize the GRO engine for UDP-tunneled traffic, for a 10% performance improvement in related stream tests. - Cover more per-CPU storage with local nested BH locking; this is a prep work to remove the current per-CPU lock in local_bh_disable() on PREMPT_RT. - Introduce and use nlmsg_payload helper, combining buffer bounds verification with accessing payload carried by netlink messages. Netfilter: - Rewrite the procfs conntrack table implementation, improving considerably the dump performance. A lot of user-space tools still use this interface. - Implement support for wildcard netdevice in netdev basechain and flowtables. - Integrate conntrack information into nft trace infrastructure. - Export set count and backend name to userspace, for better introspection. BPF: - BPF qdisc support: BPF-qdisc can be implemented with BPF struct_ops programs and can be controlled in similar way to traditional qdiscs using the "tc qdisc" command. - Refactor the UDP socket iterator, addressing long standing issues WRT duplicate hits or missed sockets. Protocols: - Improve TCP receive buffer auto-tuning and increase the default upper bound for the receive buffer; overall this improves the single flow maximum thoughput on 200Gbs link by over 60%. - Add AFS GSSAPI security class to AF_RXRPC; it provides transport security for connections to the AFS fileserver and VL server. - Improve TCP multipath routing, so that the sources address always matches the nexthop device. - Introduce SO_PASSRIGHTS for AF_UNIX, to allow disabling SCM_RIGHTS, and thus preventing DoS caused by passing around problematic FDs. - Retire DCCP socket. DCCP only receives updates for bugs, and major distros disable it by default. Its removal allows for better organisation of TCP fields to reduce the number of cache lines hit in the fast path. - Extend TCP drop-reason support to cover PAWS checks. Driver API: - Reorganize PTP ioctl flag support to require an explicit opt-in for the drivers, avoiding the problem of drivers not rejecting new unsupported flags. - Converted several device drivers to timestamping APIs. - Introduce per-PHY ethtool dump helpers, improving the support for dump operations targeting PHYs. Tests and tooling: - Add support for classic netlink in user space C codegen, so that ynl-c can now read, create and modify links, routes addresses and qdisc layer configuration. - Add ynl sub-types for binary attributes, allowing ynl-c to output known struct instead of raw binary data, clarifying the classic netlink output. - Extend MPTCP selftests to improve the code-coverage. - Add tests for XDP tail adjustment in AF_XDP. New hardware / drivers: - OpenVPN virtual driver: offload OpenVPN data channels processing to the kernel-space, increasing the data transfer throughput WRT the user-space implementation. - Renesas glue driver for the gigabit ethernet RZ/V2H(P) SoC. - Broadcom asp-v3.0 ethernet driver. - AMD Renoir ethernet device. - ReakTek MT9888 2.5G ethernet PHY driver. - Aeonsemi 10G C45 PHYs driver. Drivers: - Ethernet high-speed NICs: - nVidia/Mellanox (mlx5): - refactor the steering table handling to significantly reduce the amount of memory used - add support for complex matches in H/W flow steering - improve flow streeing error handling - convert to netdev instance locking - Intel (100G, ice, igb, ixgbe, idpf): - ice: add switchdev support for LLDP traffic over VF - ixgbe: add firmware manipulation and regions devlink support - igb: introduce support for frame transmission premption - igb: adds persistent NAPI configuration - idpf: introduce RDMA support - idpf: add initial PTP support - Meta (fbnic): - extend hardware stats coverage - add devlink dev flash support - Broadcom (bnxt): - add support for RX-side device memory TCP - Wangxun (txgbe): - implement support for udp tunnel offload - complete PTP and SRIOV support for AML 25G/10G devices - Ethernet NICs embedded and virtual: - Google (gve): - add device memory TCP TX support - Amazon (ena): - support persistent per-NAPI config - Airoha: - add H/W support for L2 traffic offload - add per flow stats for flow offloading - RealTek (rtl8211): add support for WoL magic packet - Synopsys (stmmac): - dwmac-socfpga 1000BaseX support - add Loongson-2K3000 support - introduce support for hardware-accelerated VLAN stripping - Broadcom (bcmgenet): - expose more H/W stats - Freescale (enetc, dpaa2-eth): - enetc: add MAC filter, VLAN filter RSS and loopback support - dpaa2-eth: convert to H/W timestamping APIs - vxlan: convert FDB table to rhashtable, for better scalabilty - veth: apply qdisc backpressure on full ring to reduce TX drops - Ethernet switches: - Microchip (kzZ88x3): add ETS scheduler support - Ethernet PHYs: - RealTek (rtl8211): - add support for WoL magic packet - add support for PHY LEDs - CAN: - Adds RZ/G3E CANFD support to the rcar_canfd driver. - Preparatory work for CAN-XL support. - Add self-tests framework with support for CAN physical interfaces. - WiFi: - mac80211: - scan improvements with multi-link operation (MLO) - Qualcomm (ath12k): - enable AHB support for IPQ5332 - add monitor interface support to QCN9274 - add multi-link operation support to WCN7850 - add 802.11d scan offload support to WCN7850 - monitor mode for WCN7850, better 6 GHz regulatory - Qualcomm (ath11k): - restore hibernation support - MediaTek (mt76): - WiFi-7 improvements - implement support for mt7990 - Intel (iwlwifi): - enhanced multi-link single-radio (EMLSR) support on 5 GHz links - rework device configuration - RealTek (rtw88): - improve throughput for RTL8814AU - RealTek (rtw89): - add multi-link operation support - STA/P2P concurrency improvements - support different SAR configs by antenna - Bluetooth: - introduce HCI Driver protocol - btintel_pcie: do not generate coredump for diagnostic events - btusb: add HCI Drv commands for configuring altsetting - btusb: add RTL8851BE device 0x0bda:0xb850 - btusb: add new VID/PID 13d3/3584 for MT7922 - btusb: add new VID/PID 13d3/3630 and 13d3/3613 for MT7925 - btnxpuart: implement host-wakeup feature" * tag 'net-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1611 commits) selftests/bpf: Fix bpf selftest build warning selftests: netfilter: Fix skip of wildcard interface test net: phy: mscc: Stop clearing the the UDPv4 checksum for L2 frames net: openvswitch: Fix the dead loop of MPLS parse calipso: Don't call calipso functions for AF_INET sk. selftests/tc-testing: Add a test for HFSC eltree double add with reentrant enqueue behaviour on netem net_sched: hfsc: Address reentrant enqueue adding class to eltree twice octeontx2-pf: QOS: Refactor TC_HTB_LEAF_DEL_LAST callback octeontx2-pf: QOS: Perform cache sync on send queue teardown net: mana: Add support for Multi Vports on Bare metal net: devmem: ncdevmem: remove unused variable net: devmem: ksft: upgrade rx test to send 1K data net: devmem: ksft: add 5 tuple FS support net: devmem: ksft: add exit_wait to make rx test pass net: devmem: ksft: add ipv4 support net: devmem: preserve sockc_err page_pool: fix ugly page_pool formatting net: devmem: move list_add to net_devmem_bind_dmabuf. selftests: netfilter: nft_queue.sh: include file transfer duration in log message net: phy: mscc: Fix memory leak when using one step timestamping ...

mm: convert do_set_pmd() to take a folio

2025-05-22T21:55:37Z

In do_set_pmd(), we always use the folio->page to build PMD mappings for the entire folio. Since all callers of do_set_pmd() already hold a stable folio, converting do_set_pmd() to take a folio is safe and more straightforward. In addition, to ensure the extensibility of do_set_pmd() for supporting larger folios beyond PMD size, we keep the 'page' parameter to specify which page within the folio should be mapped. No functional changes expected. Link: https://lkml.kernel.org/r/9b488f4ecb4d3fd8634e3d448dd0ed6964482480.1747017104.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Reviewed-by: Zi Yan Acked-by: David Hildenbrand Cc: Dev Jain Cc: Johannes Weiner Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Mariano Pache Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm: remove VM_PAT

2025-05-22T21:55:37Z

It's unused, so let's remove it. Link: https://lkml.kernel.org/r/20250512123424.637989-7-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Acked-by: Ingo Molnar [x86 bits] Reviewed-by: Liam R. Howlett Cc: Andy Lutomirski Cc: Borislav Betkov Cc: Dave Airlie Cc: "H. Peter Anvin" Cc: Jani Nikula Cc: Jann Horn Cc: Jonas Lahtinen Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Peter Xu Cc: Peter Zijlstra Cc: Rodrigo Vivi Cc: Steven Rostedt Cc: Thomas Gleinxer Cc: Tvrtko Ursulin Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm: fix VM_UFFD_MINOR == VM_SHADOW_STACK on USERFAULTFD=y && ARM64_GCS=y

2025-05-21T05:49:38Z

On configs with CONFIG_ARM64_GCS=y, VM_SHADOW_STACK is bit 38. On configs with CONFIG_HAVE_ARCH_USERFAULTFD_MINOR=y (selected by CONFIG_ARM64 when CONFIG_USERFAULTFD=y), VM_UFFD_MINOR is _also_ bit 38. This bit being shared by two different VMA flags could lead to all sorts of unintended behaviors. Presumably, a process could maybe call into userfaultfd in a way that disables the shadow stack vma flag. I can't think of any attack where this would help (presumably, if an attacker tries to disable shadow stacks, they are trying to hijack control flow so can't arbitrarily call into userfaultfd yet anyway) but this still feels somewhat scary. Link: https://lkml.kernel.org/r/20250507131000.1204175-2-revest@chromium.org Fixes: ae80e1629aea ("mm: Define VM_SHADOW_STACK for arm64 when we support GCS") Signed-off-by: Florent Revest Reviewed-by: Mark Brown Cc: Borislav Betkov Cc: Brendan Jackman Cc: Catalin Marinas Cc: Florent Revest Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Thiago Jung Bauermann Cc: Thomas Gleinxer Cc: Will Deacon Cc: Signed-off-by: Andrew Morton

mm: establish mm/vma_exec.c for shared exec/mm VMA functionality

2025-05-13T06:50:48Z

Patch series "move all VMA allocation, freeing and duplication logic to mm", v3. Currently VMA allocation, freeing and duplication exist in kernel/fork.c, which is a violation of separation of concerns, and leaves these functions exposed to the rest of the kernel when they are in fact internal implementation details. Resolve this by moving this logic to mm, and making it internal to vma.c, vma.h. This also allows us, in future, to provide userland testing around this functionality. We additionally abstract dup_mmap() to mm, being careful to ensure kernel/fork.c acceses this via the mm internal header so it is not exposed elsewhere in the kernel. As part of this change, also abstract initial stack allocation performed in __bprm_mm_init() out of fs code into mm via the create_init_stack_vma(), as this code uses vm_area_alloc() and vm_area_free(). In order to do so sensibly, we introduce a new mm/vma_exec.c file, which contains the code that is shared by mm and exec. This file is added to both memory mapping and exec sections in MAINTAINERS so both sets of maintainers can maintain oversight. As part of this change, we also move relocate_vma_down() to mm/vma_exec.c so all shared mm/exec functionality is kept in one place. We add code shared between nommu and mmu-enabled configurations in order to share VMA allocation, freeing and duplication code correctly while also keeping these functions available in userland VMA testing. This is achieved by adding a mm/vma_init.c file which is also compiled by the userland tests. This patch (of 4): There is functionality that overlaps the exec and memory mapping subsystems. While it properly belongs in mm, it is important that exec maintainers maintain oversight of this functionality correctly. We can establish both goals by adding a new mm/vma_exec.c file which contains these 'glue' functions, and have fs/exec.c import them. As a part of this change, to ensure that proper oversight is achieved, add the file to both the MEMORY MAPPING and EXEC & BINFMT API, ELF sections. scripts/get_maintainer.pl can correctly handle files in multiple entries and this neatly handles the cross-over. [akpm@linux-foundation.org: fix comment typo] Link: https://lkml.kernel.org/r/80f0d0c6-0b68-47f9-ab78-0ab7f74677fc@lucifer.local Link: https://lkml.kernel.org/r/cover.1745853549.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/91f2cee8f17d65214a9d83abb7011aa15f1ea690.1745853549.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Reviewed-by: Suren Baghdasaryan Reviewed-by: Pedro Falcato Reviewed-by: David Hildenbrand Reviewed-by: Kees Cook Reviewed-by: Vlastimil Babka Cc: Al Viro Cc: Christian Brauner Cc: Jan Kara Cc: Jann Horn Signed-off-by: Andrew Morton

mm: add folio_expected_ref_count() for reference count calculation

2025-05-13T06:50:46Z

Patch series " JFS: Implement migrate_folio for jfs_metapage_aops" v5. This patchset addresses a warning that occurs during memory compaction due to JFS's missing migrate_folio operation. The warning was introduced by commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added explicit warnings when filesystem don't implement migrate_folio. The syzbot reported following [1]: jfs_metapage_aops does not implement migrate_folio WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline] WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007 Modules linked in: CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline] RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007 To fix this issue, this series implement metapage_migrate_folio() for JFS which handles both single and multiple metapages per page configurations. While most filesystems leverage existing migration implementations like filemap_migrate_folio(), buffer_migrate_folio_norefs() or buffer_migrate_folio() (which internally used folio_expected_refs()), JFS's metapage architecture requires special handling of its private data during migration. To support this, this series introduce the folio_expected_ref_count(), which calculates external references to a folio from page/swap cache, private data, and page table mappings. This standardized implementation replaces the previous ad-hoc folio_expected_refs() function and enables JFS to accurately determine whether a folio has unexpected references before attempting migration. Implement folio_expected_ref_count() to calculate expected folio reference counts from: - Page/swap cache (1 per page) - Private data (1) - Page table mappings (1 per map) While originally needed for page migration operations, this improved implementation standardizes reference counting by consolidating all refcount contributors into a single, reusable function that can benefit any subsystem needing to detect unexpected references to folios. The folio_expected_ref_count() returns the sum of these external references without including any reference the caller itself might hold. Callers comparing against the actual folio_ref_count() must account for their own references separately. Link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299 [1] Link: https://lkml.kernel.org/r/20250430100150.279751-1-shivankg@amd.com Link: https://lkml.kernel.org/r/20250430100150.279751-2-shivankg@amd.com Signed-off-by: David Hildenbrand Signed-off-by: Shivank Garg Suggested-by: Matthew Wilcox Co-developed-by: David Hildenbrand Cc: Alistair Popple Cc: Dave Kleikamp Cc: Donet Tom Cc: Jane Chu Cc: Kefeng Wang Cc: Zi Yan Signed-off-by: Andrew Morton