kernel/linux.git/drivers/dax/bus.c, branch v6.6.133

dax: Cleanup extra dax_region references

2023-06-23T07:03:50+00:00

Now that free_dev_dax_id() internally manages the references it needs the extra references taken by the dax_region drivers are not needed. Reported-by: Ira Weiny Signed-off-by: Dan Williams Link: https://lore.kernel.org/r/168577285161.1672036.8111253437794419696.stgit@dwillia2-xfh.jf.intel.com Reviewed-by: Dave Jiang Reviewed-by: Fan Ni Reviewed-by: Ira Weiny Signed-off-by: Vishal Verma

dax: Introduce alloc_dev_dax_id()

2023-06-23T07:03:50+00:00

The reference counting of dax_region objects is needlessly complicated, has lead to confusion [1], and has hidden a bug [2]. Towards cleaning up that mess introduce alloc_dev_dax_id() to minimize the holding of a dax_region reference to only what dev_dax_release() needs, the dax_region->ida. Part of the reason for the mess was the design to dereference a dax_region in all cases in free_dev_dax_id() even if the id was statically assigned by the upper level dax_region driver. Remove the need to call "is_static(dax_region)" by tracking whether the id is dynamic directly in the dev_dax instance itself. With that flag the dax_region pinning and release per dev_dax instance can move to alloc_dev_dax_id() and free_dev_dax_id() respectively. A follow-on cleanup address the unnecessary references in the dax_region setup and drivers. Fixes: 0f3da14a4f05 ("device-dax: introduce 'seed' devices") Link: http://lore.kernel.org/r/20221203095858.612027-1-liuyongqiang13@huawei.com [1] Link: http://lore.kernel.org/r/3cf0890b-4eb0-e70e-cd9c-2ecc3d496263@hpe.com [2] Reported-by: Yongqiang Liu Reported-by: Paul Cassella Reported-by: Ira Weiny Signed-off-by: Dan Williams Link: https://lore.kernel.org/r/168577284563.1672036.13493034988900989554.stgit@dwillia2-xfh.jf.intel.com Reviewed-by: Ira Weiny Signed-off-by: Vishal Verma

dax: Use device_unregister() in unregister_dax_mapping()

2023-06-23T07:03:50+00:00

Replace an open-coded device_unregister() sequence with the helper. Signed-off-by: Dan Williams Link: https://lore.kernel.org/r/168577283989.1672036.7777592498865470652.stgit@dwillia2-xfh.jf.intel.com Reviewed-by: Dave Jiang Reviewed-by: Fan Ni Reviewed-by: Ira Weiny Signed-off-by: Vishal Verma

dax: Fix dax_mapping_release() use after free

2023-06-23T07:03:50+00:00

A CONFIG_DEBUG_KOBJECT_RELEASE test of removing a device-dax region provider (like modprobe -r dax_hmem) yields: kobject: 'mapping0' (ffff93eb460e8800): kobject_release, parent 0000000000000000 (delayed 2000) [..] DEBUG_LOCKS_WARN_ON(1) WARNING: CPU: 23 PID: 282 at kernel/locking/lockdep.c:232 __lock_acquire+0x9fc/0x2260 [..] RIP: 0010:__lock_acquire+0x9fc/0x2260 [..] Call Trace: [..] lock_acquire+0xd4/0x2c0 ? ida_free+0x62/0x130 _raw_spin_lock_irqsave+0x47/0x70 ? ida_free+0x62/0x130 ida_free+0x62/0x130 dax_mapping_release+0x1f/0x30 device_release+0x36/0x90 kobject_delayed_cleanup+0x46/0x150 Due to attempting ida_free() on an ida object that has already been freed. Devices typically only hold a reference on their parent while registered. If a child needs a parent object to complete its release it needs to hold a reference that it drops from its release callback. Arrange for a dax_mapping to pin its parent dev_dax instance until dax_mapping_release(). Fixes: 0b07ce872a9e ("device-dax: introduce 'mapping' devices") Signed-off-by: Dan Williams Link: https://lore.kernel.org/r/168577283412.1672036.16111545266174261446.stgit@dwillia2-xfh.jf.intel.com Reviewed-by: Dave Jiang Reviewed-by: Fan Ni Reviewed-by: Ira Weiny Signed-off-by: Vishal Verma

Merge tag 'cxl-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl

2023-02-25T17:19:23+00:00

Pull Compute Express Link (CXL) updates from Dan Williams: "To date Linux has been dependent on platform-firmware to map CXL RAM regions and handle events / errors from devices. With this update we can now parse / update the CXL memory layout, and report events / errors from devices. This is a precursor for the CXL subsystem to handle the end-to-end "RAS" flow for CXL memory. i.e. the flow that for DDR-attached-DRAM is handled by the EDAC driver where it maps system physical address events to a field-replaceable-unit (FRU / endpoint device). In general, CXL has the potential to standardize what has historically been a pile of memory-controller-specific error handling logic. Another change of note is the default policy for handling RAM-backed device-dax instances. Previously the default access mode was "device", mmap(2) a device special file to access memory. The new default is "kmem" where the address range is assigned to the core-mm via add_memory_driver_managed(). This saves typical users from wondering why their platform memory is not visible via free(1) and stuck behind a device-file. At the same time it allows expert users to deploy policy to, for example, get dedicated access to high performance memory, or hide low performance memory from general purpose kernel allocations. This affects not only CXL, but also systems with high-bandwidth-memory that platform-firmware tags with the EFI_MEMORY_SP (special purpose) designation. Summary: - CXL RAM region enumeration: instantiate 'struct cxl_region' objects for platform firmware created memory regions - CXL RAM region provisioning: complement the existing PMEM region creation support with RAM region support - "Soft Reservation" policy change: Online (memory hot-add) soft-reserved memory (EFI_MEMORY_SP) by default, but still allow for setting aside such memory for dedicated access via device-dax. - CXL Events and Interrupts: Takeover CXL event handling from platform-firmware (ACPI calls this CXL Memory Error Reporting) and export CXL Events via Linux Trace Events. - Convey CXL _OSC results to drivers: Similar to PCI, let the CXL subsystem interrogate the result of CXL _OSC negotiation. - Emulate CXL DVSEC Range Registers as "decoders": Allow for first-generation devices that pre-date the definition of the CXL HDM Decoder Capability to translate the CXL DVSEC Range Registers into 'struct cxl_decoder' objects. - Set timestamp: Per spec, set the device timestamp in case of hotplug, or if platform-firwmare failed to set it. - General fixups: linux-next build issues, non-urgent fixes for pre-production hardware, unit test fixes, spelling and debug message improvements" * tag 'cxl-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl: (66 commits) dax/kmem: Fix leak of memory-hotplug resources cxl/mem: Add kdoc param for event log driver state cxl/trace: Add serial number to trace points cxl/trace: Add host output to trace points cxl/trace: Standardize device information output cxl/pci: Remove locked check for dvsec_range_allowed() cxl/hdm: Add emulation when HDM decoders are not committed cxl/hdm: Create emulated cxl_hdm for devices that do not have HDM decoders cxl/hdm: Emulate HDM decoder from DVSEC range registers cxl/pci: Refactor cxl_hdm_decode_init() cxl/port: Export cxl_dvsec_rr_decode() to cxl_port cxl/pci: Break out range register decoding from cxl_hdm_decode_init() cxl: add RAS status unmasking for CXL cxl: remove unnecessary calling of pci_enable_pcie_error_reporting() dax/hmem: build hmem device support as module if possible dax: cxl: add CXL_REGION dependency cxl: avoid returning uninitialized error code cxl/pmem: Fix nvdimm registration races cxl/mem: Fix UAPI command comment cxl/uapi: Tag commands from cxl_query_cmd() ...

dax/kmem: Fix leak of memory-hotplug resources

2023-02-17T22:58:01+00:00

While experimenting with CXL region removal the following corruption of /proc/iomem appeared. Before: f010000000-f04fffffff : CXL Window 0 f010000000-f02fffffff : region4 f010000000-f02fffffff : dax4.0 f010000000-f02fffffff : System RAM (kmem) After (modprobe -r cxl_test): f010000000-f02fffffff : **redacted binary garbage** f010000000-f02fffffff : System RAM (kmem) ...and testing further the same is visible with persistent memory assigned to kmem: Before: 480000000-243fffffff : Persistent Memory 480000000-57e1fffff : namespace3.0 580000000-243fffffff : dax3.0 580000000-243fffffff : System RAM (kmem) After (ndctl disable-region all): 480000000-243fffffff : Persistent Memory 580000000-243fffffff : ***redacted binary garbage*** 580000000-243fffffff : System RAM (kmem) The corrupted data is from a use-after-free of the "dax4.0" and "dax3.0" resources, and it also shows that the "System RAM (kmem)" resource is not being removed. The bug does not appear after "modprobe -r kmem", it requires the parent of "dax4.0" and "dax3.0" to be removed which re-parents the leaked "System RAM (kmem)" instances. Those in turn reference the freed resource as a parent. First up for the fix is release_mem_region_adjustable() needs to reliably delete the resource inserted by add_memory_driver_managed(). That is thwarted by a check for IORESOURCE_SYSRAM that predates the dax/kmem driver, from commit: 65c78784135f ("kernel, resource: check for IORESOURCE_SYSRAM in release_mem_region_adjustable") That appears to be working around the behavior of HMM's "MEMORY_DEVICE_PUBLIC" facility that has since been deleted. With that check removed the "System RAM (kmem)" resource gets removed, but corruption still occurs occasionally because the "dax" resource is not reliably removed. The dax range information is freed before the device is unregistered, so the driver can not reliably recall (another use after free) what it is meant to release. Lastly if that use after free got lucky, the driver was covering up the leak of "System RAM (kmem)" due to its use of release_resource() which detaches, but does not free, child resources. The switch to remove_resource() forces remove_memory() to be responsible for the deletion of the resource added by add_memory_driver_managed(). Fixes: c2f3011ee697 ("device-dax: add an allocation interface for device-dax instances") Cc: Cc: Oscar Salvador Cc: David Hildenbrand Cc: Pavel Tatashin Reviewed-by: Vishal Verma Reviewed-by: Pasha Tatashin Reviewed-by: Dave Jiang Link: https://lore.kernel.org/r/167653656244.3147810.5705900882794040229.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams

dax: Assign RAM regions to memory-hotplug by default

2023-02-11T01:33:40+00:00

The default mode for device-dax instances is backwards for RAM-regions as evidenced by the fact that it tends to catch end users by surprise. "Where is my memory?". Recall that platforms are increasingly shipping with performance-differentiated memory pools beyond typical DRAM and NUMA effects. This includes HBM (high-bandwidth-memory) and CXL (dynamic interleave, varied media types, and future fabric attached possibilities). For this reason the EFI_MEMORY_SP (EFI Special Purpose Memory => Linux 'Soft Reserved') attribute is expected to be applied to all memory-pools that are not the general purpose pool. This designation gives an Operating System a chance to defer usage of a memory pool until later in the boot process where its performance properties can be interrogated and administrator policy can be applied. 'Soft Reserved' memory can be anything from too limited and precious to be part of the general purpose pool (HBM), too slow to host hot kernel data structures (some PMEM media), or anything in between. However, in the absence of an explicit policy, the memory should at least be made usable by default. The current device-dax default hides all non-general-purpose memory behind a device interface. The expectation is that the distribution of users that want the memory online by default vs device-dedicated-access by default follows the Pareto principle. A small number of enlightened users may want to do userspace memory management through a device, but general users just want the kernel to make the memory available with an option to get more advanced later. Arrange for all device-dax instances not backed by PMEM to default to attaching to the dax_kmem driver. From there the baseline memory hotplug policy (CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE / memhp_default_state=) gates whether the memory comes online or stays offline. Where, if it stays offline, it can be reliably converted back to device-mode where it can be partitioned, or fronted by a userspace allocator. So, if someone wants device-dax instances for their 'Soft Reserved' memory: 1/ Build a kernel with CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=n or boot with memhp_default_state=offline, or roll the dice and hope that the kernel has not pinned a page in that memory before step 2. 2/ Write a udev rule to convert the target dax device(s) from 'system-ram' mode to 'devdax' mode: daxctl reconfigure-device $dax -m devdax -f Cc: Michal Hocko Cc: David Hildenbrand Cc: Dave Hansen Reviewed-by: Gregory Price Tested-by: Fan Ni Reviewed-by: Dave Jiang Link: https://lore.kernel.org/r/167602003336.1924368.6809503401422267885.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams

driver core: make struct bus_type.uevent() take a const *

2023-01-27T12:45:52+00:00

The uevent() callback in struct bus_type should not be modifying the device that is passed into it, so mark it as a const * and propagate the function signature changes out into all relevant subsystems that use this callback. Acked-by: Rafael J. Wysocki Acked-by: Hans de Goede Link: https://lore.kernel.org/r/20230111113018.459199-16-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman

Merge branch 'akpm' (patches from Andrew)

2022-01-15T18:37:06+00:00

Merge misc updates from Andrew Morton: "146 patches. Subsystems affected by this patch series: kthread, ia64, scripts, ntfs, squashfs, ocfs2, vfs, and mm (slab-generic, slab, kmemleak, dax, kasan, debug, pagecache, gup, shmem, frontswap, memremap, memcg, selftests, pagemap, dma, vmalloc, memory-failure, hugetlb, userfaultfd, vmscan, mempolicy, oom-kill, hugetlbfs, migration, thp, ksm, page-poison, percpu, rmap, zswap, zram, cleanups, hmm, and damon)" * emailed patches from Andrew Morton : (146 commits) mm/damon: hide kernel pointer from tracepoint event mm/damon/vaddr: hide kernel pointer from damon_va_three_regions() failure log mm/damon/vaddr: use pr_debug() for damon_va_three_regions() failure logging mm/damon/dbgfs: remove an unnecessary variable mm/damon: move the implementation of damon_insert_region to damon.h mm/damon: add access checking for hugetlb pages Docs/admin-guide/mm/damon/usage: update for schemes statistics mm/damon/dbgfs: support all DAMOS stats Docs/admin-guide/mm/damon/reclaim: document statistics parameters mm/damon/reclaim: provide reclamation statistics mm/damon/schemes: account how many times quota limit has exceeded mm/damon/schemes: account scheme actions that successfully applied mm/damon: remove a mistakenly added comment for a future feature Docs/admin-guide/mm/damon/usage: update for kdamond_pid and (mk|rm)_contexts Docs/admin-guide/mm/damon/usage: mention tracepoint at the beginning Docs/admin-guide/mm/damon/usage: remove redundant information Docs/admin-guide/mm/damon/usage: update for scheme quotas and watermarks mm/damon: convert macro functions to static inline functions mm/damon: modify damon_rand() macro to static inline function mm/damon: move damon_rand() definition into damon.h ...

device-dax: ensure dev_dax->pgmap is valid for dynamic devices

2022-01-15T14:30:25+00:00

Right now, only static dax regions have a valid @pgmap pointer in its struct dev_dax. Dynamic dax case however, do not. In preparation for device-dax compound devmap support, make sure that dev_dax pgmap field is set after it has been allocated and initialized. dynamic dax device have the @pgmap is allocated at probe() and it's managed by devm (contrast to static dax region which a pgmap is provided and dax core kfrees it). So in addition to ensure a valid @pgmap, clear the pgmap when the dynamic dax device is released to avoid the same pgmap ranges to be re-requested across multiple region device reconfigs. Add a static_dev_dax() and use that helper in dev_dax_probe() to ensure the initialization differences between dynamic and static regions are more explicit. While at it, consolidate the ranges initialization when we allocate the @pgmap for the dynamic dax region case. Also take the opportunity to document the differences between static and dynamic da regions. Link: https://lkml.kernel.org/r/20211202204422.26777-8-joao.m.martins@oracle.com Suggested-by: Dan Williams Signed-off-by: Joao Martins Cc: Christoph Hellwig Cc: Dave Jiang Cc: Jane Chu Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: John Hubbard Cc: Jonathan Corbet Cc: Matthew Wilcox (Oracle) Cc: Mike Kravetz Cc: Muchun Song Cc: Naoya Horiguchi Cc: Vishal Verma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds