user/sven/linux.git/mm, branch v5.4.140

mm: slab: fix kmem_cache_create failed when sysfs node not destroyed

2021-07-25T12:35:14Z

The commit d38a2b7a9c93 ("mm: memcg/slab: fix memory leak at non-root kmem_cache destroy") introduced a problem: If one thread destroy a kmem_cache A and another thread concurrently create a kmem_cache B, which is mergeable with A and has same size with A, the B may fail to create due to the duplicate sysfs node. The scenario in detail: 1) Thread 1 uses kmem_cache_destroy() to destroy kmem_cache A which is mergeable, it decreases A's refcount and if refcount is 0, then call memcg_set_kmem_cache_dying() which set A->memcg_params.dying = true, then unlock the slab_mutex and call flush_memcg_workqueue(), it may cost a while. Note: now the sysfs node(like '/kernel/slab/:0000248') of A is still present, it will be deleted in shutdown_cache() which will be called after flush_memcg_workqueue() is done and lock the slab_mutex again. 2) Now if thread 2 is coming, it use kmem_cache_create() to create B, which is mergeable with A(their size is same), it gain the lock of slab_mutex, then call __kmem_cache_alias() trying to find a mergeable node, because of the below added code in commit d38a2b7a9c93 ("mm: memcg/slab: fix memory leak at non-root kmem_cache destroy"), B is not mergeable with A whose memcg_params.dying is true. int slab_unmergeable(struct kmem_cache *s) if (s->refcount < 0) return 1; /* * Skip the dying kmem_cache. */ if (s->memcg_params.dying) return 1; return 0; } So B has to create its own sysfs node by calling: create_cache-> __kmem_cache_create-> sysfs_slab_add-> kobject_init_and_add Because B is mergeable itself, its filename of sysfs node is based on its size, like '/kernel/slab/:0000248', which is duplicate with A, and the sysfs node of A is still present now, so kobject_init_and_add() will return fail and result in kmem_cache_create() fail. Concurrently modprobe and rmmod the two modules below can reproduce the issue quickly: nf_conntrack_expect, se_sess_cache. See call trace in the end. LTS versions of v4.19.y and v5.4.y have this problem, whereas linux versions after v5.9 do not have this problem because the patchset: ("The new cgroup slab memory controller") almost refactored memcg slab. A potential solution(this patch belongs): Just let the dying kmem_cache be mergeable, the slab_mutex lock can prevent the race between alias kmem_cache creating thread and root kmem_cache destroying thread. In the destroying thread, after flush_memcg_workqueue() is done, judge the refcount again, if someone reference it again during un-lock time, we don't need to destroy the kmem_cache completely, we can reuse it. Another potential solution: revert the commit d38a2b7a9c93 ("mm: memcg/slab: fix memory leak at non-root kmem_cache destroy"), compare to the fail of kmem_cache_create, the memory leak in special scenario seems less harmful. Call trace: sysfs: cannot create duplicate filename '/kernel/slab/:0000248' Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: dump_backtrace+0x0/0x198 show_stack+0x24/0x30 dump_stack+0xb0/0x100 sysfs_warn_dup+0x6c/0x88 sysfs_create_dir_ns+0x104/0x120 kobject_add_internal+0xd0/0x378 kobject_init_and_add+0x90/0xd8 sysfs_slab_add+0x16c/0x2d0 __kmem_cache_create+0x16c/0x1d8 create_cache+0xbc/0x1f8 kmem_cache_create_usercopy+0x1a0/0x230 kmem_cache_create+0x50/0x68 init_se_kmem_caches+0x38/0x258 [target_core_mod] target_core_init_configfs+0x8c/0x390 [target_core_mod] do_one_initcall+0x54/0x230 do_init_module+0x64/0x1ec load_module+0x150c/0x16f0 __se_sys_finit_module+0xf0/0x108 __arm64_sys_finit_module+0x24/0x30 el0_svc_common+0x80/0x1c0 el0_svc_handler+0x78/0xe0 el0_svc+0x10/0x260 kobject_add_internal failed for :0000248 with -EEXIST, don't try to register things with the same name in the same directory. kmem_cache_create(se_sess_cache) failed with error -17 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: dump_backtrace+0x0/0x198 show_stack+0x24/0x30 dump_stack+0xb0/0x100 kmem_cache_create_usercopy+0xa8/0x230 kmem_cache_create+0x50/0x68 init_se_kmem_caches+0x38/0x258 [target_core_mod] target_core_init_configfs+0x8c/0x390 [target_core_mod] do_one_initcall+0x54/0x230 do_init_module+0x64/0x1ec load_module+0x150c/0x16f0 __se_sys_finit_module+0xf0/0x108 __arm64_sys_finit_module+0x24/0x30 el0_svc_common+0x80/0x1c0 el0_svc_handler+0x78/0xe0 el0_svc+0x10/0x260 Fixes: d38a2b7a9c93 ("mm: memcg/slab: fix memory leak at non-root kmem_cache destroy") Signed-off-by: Nanyong Sun Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

mm/z3fold: fix potential memory leak in z3fold_destroy_pool()

2021-07-14T14:53:47Z

[ Upstream commit dac0d1cfda56472378d330b1b76b9973557a7b1d ] There is a memory leak in z3fold_destroy_pool() as it forgets to free_percpu pool->unbuddied. Call free_percpu for pool->unbuddied to fix this issue. Link: https://lkml.kernel.org/r/20210619093151.1492174-6-linmiaohe@huawei.com Fixes: d30561c56f41 ("z3fold: use per-cpu unbuddied lists") Signed-off-by: Miaohe Lin Reviewed-by: Vitaly Wool Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm/huge_memory.c: don't discard hugepage if other processes are mapping it

2021-07-14T14:53:47Z

[ Upstream commit babbbdd08af98a59089334eb3effbed5a7a0cf7f ] If other processes are mapping any other subpages of the hugepage, i.e. in pte-mapped thp case, page_mapcount() will return 1 incorrectly. Then we would discard the page while other processes are still mapping it. Fix it by using total_mapcount() which can tell whether other processes are still mapping it. Link: https://lkml.kernel.org/r/20210511134857.1581273-6-linmiaohe@huawei.com Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Reviewed-by: Yang Shi Signed-off-by: Miaohe Lin Cc: Alexey Dobriyan Cc: "Aneesh Kumar K . V" Cc: Anshuman Khandual Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Minchan Kim Cc: Ralph Campbell Cc: Rik van Riel Cc: Song Liu Cc: William Kucharski Cc: Zi Yan Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm, futex: fix shared futex pgoff on shmem huge page

2021-06-30T12:47:55Z

[ Upstream commit fe19bd3dae3d15d2fbfdb3de8839a6ea0fe94264 ] If more than one futex is placed on a shmem huge page, it can happen that waking the second wakes the first instead, and leaves the second waiting: the key's shared.pgoff is wrong. When 3.11 commit 13d60f4b6ab5 ("futex: Take hugepages into account when generating futex_key"), the only shared huge pages came from hugetlbfs, and the code added to deal with its exceptional page->index was put into hugetlb source. Then that was missed when 4.8 added shmem huge pages. page_to_pgoff() is what others use for this nowadays: except that, as currently written, it gives the right answer on hugetlbfs head, but nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific hugetlb_basepage_index() on PageHuge tails as well as on head. Yes, it's unconventional to declare hugetlb_basepage_index() there in pagemap.h, rather than in hugetlb.h; but I do not expect anything but page_to_pgoff() ever to need it. [akpm@linux-foundation.org: give hugetlb_basepage_index() prototype the correct scope] Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Reported-by: Neel Natu Signed-off-by: Hugh Dickins Reviewed-by: Matthew Wilcox (Oracle) Acked-by: Thomas Gleixner Cc: "Kirill A. Shutemov" Cc: Zhang Yi Cc: Mel Gorman Cc: Mike Kravetz Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Darren Hart Cc: Davidlohr Bueso Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Note on stable backport: leave redundant #include in kernel/futex.c, to avoid conflict over the header files included. Signed-off-by: Hugh Dickins Signed-off-by: Greg Kroah-Hartman

mm/thp: another PVMW_SYNC fix in page_vma_mapped_walk()

2021-06-30T12:47:55Z

Aha! Shouldn't that quick scan over pte_none()s make sure that it holds ptlock in the PVMW_SYNC case? That too might have been responsible for BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though I've never seen any. Link: https://lkml.kernel.org/r/1bdf384c-8137-a149-2a1e-475a4791c3c@google.com Link: https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Tested-by: Wang Yugui Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm/thp: fix page_vma_mapped_walk() if THP mapped by ptes

2021-06-30T12:47:54Z

Running certain tests with a DEBUG_VM kernel would crash within hours, on the total_mapcount BUG() in split_huge_page_to_list(), while trying to free up some memory by punching a hole in a shmem huge page: split's try_to_unmap() was unable to find all the mappings of the page (which, on a !DEBUG_VM kernel, would then keep the huge page pinned in memory). Crash dumps showed two tail pages of a shmem huge page remained mapped by pte: ptes in a non-huge-aligned vma of a gVisor process, at the end of a long unmapped range; and no page table had yet been allocated for the head of the huge page to be mapped into. Although designed to handle these odd misaligned huge-page-mapped-by-pte cases, page_vma_mapped_walk() falls short by returning false prematurely when !pmd_present or !pud_present or !p4d_present or !pgd_present: there are cases when a huge page may span the boundary, with ptes present in the next. Restructure page_vma_mapped_walk() as a loop to continue in these cases, while keeping its layout much as before. Add a step_forward() helper to advance pvmw->address across those boundaries: originally I tried to use mm's standard p?d_addr_end() macros, but hit the same crash 512 times less often: because of the way redundant levels are folded together, but folded differently in different configurations, it was just too difficult to use them correctly; and step_forward() is simpler anyway. Link: https://lkml.kernel.org/r/fedb8632-1798-de42-f39e-873551d5bc81@google.com Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Wang Yugui Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page_vma_mapped_walk(): get vma_address_end() earlier

2021-06-30T12:47:54Z

page_vma_mapped_walk() cleanup: get THP's vma_address_end() at the start, rather than later at next_pte. It's a little unnecessary overhead on the first call, but makes for a simpler loop in the following commit. Link: https://lkml.kernel.org/r/4542b34d-862f-7cb4-bb22-e0df6ce830a2@google.com Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Wang Yugui Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page_vma_mapped_walk(): use goto instead of while (1)

2021-06-30T12:47:54Z

page_vma_mapped_walk() cleanup: add a label this_pte, matching next_pte, and use "goto this_pte", in place of the "while (1)" loop at the end. Link: https://lkml.kernel.org/r/a52b234a-851-3616-2525-f42736e8934@google.com Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Wang Yugui Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page_vma_mapped_walk(): add a level of indentation

2021-06-30T12:47:54Z

page_vma_mapped_walk() cleanup: add a level of indentation to much of the body, making no functional change in this commit, but reducing the later diff when this is all converted to a loop. [hughd@google.com: : page_vma_mapped_walk(): add a level of indentation fix] Link: https://lkml.kernel.org/r/7f817555-3ce1-c785-e438-87d8efdcaf26@google.com Link: https://lkml.kernel.org/r/efde211-f3e2-fe54-977-ef481419e7f3@google.com Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Wang Yugui Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page_vma_mapped_walk(): crossing page table boundary

2021-06-30T12:47:54Z

page_vma_mapped_walk() cleanup: adjust the test for crossing page table boundary - I believe pvmw->address is always page-aligned, but nothing else here assumed that; and remember to reset pvmw->pte to NULL after unmapping the page table, though I never saw any bug from that. Link: https://lkml.kernel.org/r/799b3f9c-2a9e-dfef-5d89-26e9f76fd97@google.com Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Wang Yugui Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman