linux/mm/memory.c, branch v5.4

mm: do not hash address in print_bad_pte()

2019-09-24T22:54:09Z

Using %px to show the actual address in print_bad_pte() to help us to debug issue. Link: http://lkml.kernel.org/r/20190831011816.141002-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: release the spinlock on zap_pte_range

2019-09-24T22:54:08Z

In our testing (camera recording), Miguel and Wei found unmap_page_range() takes above 6ms with preemption disabled easily. When I see that, the reason is it holds page table spinlock during entire 512 page operation in a PMD. 6.2ms is never trivial for user experince if RT task couldn't run in the time because it could make frame drop or glitch audio problem. I had a time to benchmark it via adding some trace_printk hooks between pte_offset_map_lock and pte_unmap_unlock in zap_pte_range. The testing device is 2018 premium mobile device. I can get 2ms delay rather easily to release 2M(ie, 512 pages) when the task runs on little core even though it doesn't have any IPI and LRU lock contention. It's already too heavy. If I remove activate_page, 35-40% overhead of zap_pte_range is gone so most of overhead(about 0.7ms) comes from activate_page via mark_page_accessed. Thus, if there are LRU contention, that 0.7ms could accumulate up to several ms. So this patch adds a check for need_resched() in the loop, and a preemption point if necessary. Link: http://lkml.kernel.org/r/20190731061440.GC155569@google.com Signed-off-by: Minchan Kim Reported-by: Miguel de Dios Reported-by: Wei Wang Reviewed-by: Andrew Morton Cc: Michal Hocko Cc: Johannes Weiner Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: remove redundant assignment of entry

2019-09-24T22:54:08Z

Since ptent will not be changed after previous assignment of entry, it is not necessary to do the assignment again. Link: http://lkml.kernel.org/r/20190708082740.21111-1-richardw.yang@linux.intel.com Signed-off-by: Wei Yang Acked-by: Matthew Wilcox (Oracle) Cc: Will Deacon Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vfs: don't allow writes to swap files

2019-08-20T14:55:16Z

Don't let userspace write to an active swap file because the kernel effectively has a long term lease on the storage and things could get seriously corrupted if we let this happen. Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig

mm: thp: make transhuge_vma_suitable available for anonymous THP

2019-07-19T00:08:06Z

transhuge_vma_suitable() was only available for shmem THP, but anonymous THP has the same check except pgoff check. And, it will be used for THP eligible check in the later patch, so make it available for all kind of THPs. This also helps reduce code duplication slightly. Since anonymous THP doesn't have to check pgoff, so make pgoff check shmem vma only. And regroup some functions in include/linux/mm.h to solve compile issue since transhuge_vma_suitable() needs call vma_is_anonymous() which was defined after huge_mm.h is included. [akpm@linux-foundation.org: fix typo] [yang.shi@linux.alibaba.com: v4] Link: http://lkml.kernel.org/r/1563400758-124759-2-git-send-email-yang.shi@linux.alibaba.com Link: http://lkml.kernel.org/r/1560401041-32207-2-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi Acked-by: Hugh Dickins Cc: Kirill A. Shutemov Cc: Michal Hocko Cc: Vlastimil Babka Cc: David Rientjes Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma

2019-07-15T02:42:11Z

Pull HMM updates from Jason Gunthorpe: "Improvements and bug fixes for the hmm interface in the kernel: - Improve clarity, locking and APIs related to the 'hmm mirror' feature merged last cycle. In linux-next we now see AMDGPU and nouveau to be using this API. - Remove old or transitional hmm APIs. These are hold overs from the past with no users, or APIs that existed only to manage cross tree conflicts. There are still a few more of these cleanups that didn't make the merge window cut off. - Improve some core mm APIs: - export alloc_pages_vma() for driver use - refactor into devm_request_free_mem_region() to manage DEVICE_PRIVATE resource reservations - refactor duplicative driver code into the core dev_pagemap struct - Remove hmm wrappers of improved core mm APIs, instead have drivers use the simplified API directly - Remove DEVICE_PUBLIC - Simplify the kconfig flow for the hmm users and core code" * tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (42 commits) mm: don't select MIGRATE_VMA_HELPER from HMM_MIRROR mm: remove the HMM config option mm: sort out the DEVICE_PRIVATE Kconfig mess mm: simplify ZONE_DEVICE page private data mm: remove hmm_devmem_add mm: remove hmm_vma_alloc_locked_page nouveau: use devm_memremap_pages directly nouveau: use alloc_page_vma directly PCI/P2PDMA: use the dev_pagemap internal refcount device-dax: use the dev_pagemap internal refcount memremap: provide an optional internal refcount in struct dev_pagemap memremap: replace the altmap_valid field with a PGMAP_ALTMAP_VALID flag memremap: remove the data field in struct dev_pagemap memremap: add a migrate_to_ram method to struct dev_pagemap_ops memremap: lift the devmap_enable manipulation into devm_memremap_pages memremap: pass a struct dev_pagemap to ->kill and ->cleanup memremap: move dev_pagemap callbacks into a separate structure memremap: validate the pagemap type passed to devm_memremap_pages mm: factor out a devm_request_free_mem_region helper mm: export alloc_pages_vma ...

mm: use down_read_killable for locking mmap_sem in access_remote_vm

2019-07-12T18:05:47Z

This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Access_remote_vm never returns error codes, all errors are ignored and only size of successfully read data is returned. So, if current task was killed we'll simply return 0 (bytes read). Mmap_sem could be locked for a long time or forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. Link: http://lkml.kernel.org/r/156007494202.3335.16782303099589302087.stgit@buzz Signed-off-by: Konstantin Khlebnikov Reviewed-by: Michal Koutný Acked-by: Oleg Nesterov Acked-by: Michal Hocko Cc: Alexey Dobriyan Cc: Matthew Wilcox Cc: Cyrill Gorcunov Cc: Kirill Tkhai Cc: Al Viro Cc: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/memory.c: fail when offset == num in first check of __vm_map_pages()

2019-07-12T18:05:46Z

If the caller asks us for offset == num, we should already fail in the first check, i.e. the one testing for offsets beyond the object. At the moment, we are failing on the second test anyway, since count cannot be 0. Still, to agree with the comment of the first test, we should first test it there. Link: http://lkml.kernel.org/r/20190528193004.GA7744@gmail.com Signed-off-by: Miguel Ojeda Reviewed-by: Andrew Morton Cc: Souptick Joarder Cc: Matthew Wilcox Cc: Peter Zijlstra Cc: "Aneesh Kumar K.V" Cc: Huang Ying Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/pgtable: drop pgtable_t variable from pte_fn_t functions

2019-07-12T18:05:46Z

Drop the pgtable_t variable from all implementation for pte_fn_t as none of them use it. apply_to_pte_range() should stop computing it as well. Should help us save some cycles. Link: http://lkml.kernel.org/r/1556803126-26596-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Anshuman Khandual Acked-by: Matthew Wilcox Cc: Ard Biesheuvel Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Michal Hocko Cc: Logan Gunthorpe Cc: "Kirill A. Shutemov" Cc: Dan Williams Cc: Cc: Mike Rapoport Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, swap: fix race between swapoff and some swap operations

2019-07-12T18:05:43Z

When swapin is performed, after getting the swap entry information from the page table, system will swap in the swap entry, without any lock held to prevent the swap device from being swapoff. This may cause the race like below, CPU 1 CPU 2 ----- ----- do_swap_page swapin_readahead __read_swap_cache_async swapoff swapcache_prepare p->swap_map = NULL __swap_duplicate p->swap_map[?] /* !!! NULL pointer access */ Because swapoff is usually done when system shutdown only, the race may not hit many people in practice. But it is still a race need to be fixed. To fix the race, get_swap_device() is added to check whether the specified swap entry is valid in its swap device. If so, it will keep the swap entry valid via preventing the swap device from being swapoff, until put_swap_device() is called. Because swapoff() is very rare code path, to make the normal path runs as fast as possible, rcu_read_lock/unlock() and synchronize_rcu() instead of reference count is used to implement get/put_swap_device(). >From get_swap_device() to put_swap_device(), RCU reader side is locked, so synchronize_rcu() in swapoff() will wait until put_swap_device() is called. In addition to swap_map, cluster_info, etc. data structure in the struct swap_info_struct, the swap cache radix tree will be freed after swapoff, so this patch fixes the race between swap cache looking up and swapoff too. Races between some other swap cache usages and swapoff are fixed too via calling synchronize_rcu() between clearing PageSwapCache() and freeing swap cache data structure. Another possible method to fix this is to use preempt_off() + stop_machine() to prevent the swap device from being swapoff when its data structure is being accessed. The overhead in hot-path of both methods is similar. The advantages of RCU based method are, 1. stop_machine() may disturb the normal execution code path on other CPUs. 2. File cache uses RCU to protect its radix tree. If the similar mechanism is used for swap cache too, it is easier to share code between them. 3. RCU is used to protect swap cache in total_swapcache_pages() and exit_swap_address_space() already. The two mechanisms can be merged to simplify the logic. Link: http://lkml.kernel.org/r/20190522015423.14418-1-ying.huang@intel.com Fixes: 235b62176712 ("mm/swap: add cluster lock") Signed-off-by: "Huang, Ying" Reviewed-by: Andrea Parri Not-nacked-by: Hugh Dickins Cc: Andrea Arcangeli Cc: Paul E. McKenney Cc: Daniel Jordan Cc: Michal Hocko Cc: Minchan Kim Cc: Johannes Weiner Cc: Tim Chen Cc: Mel Gorman Cc: Jérôme Glisse Cc: Yang Shi Cc: David Rientjes Cc: Rik van Riel Cc: Jan Kara Cc: Dave Jiang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds