Patch series "mm: allow mapping accounted kernel pages to userspace", v6. Currently a non-slab kernel page which has been charged to a memory cgroup can't be mapped to userspace. The underlying reason is simple: PageKmemcg flag is defined as a page type (like buddy, offline, etc), so it takes a bit from a page->mapped counter. Pages with a type set can't be mapped to userspace. But in general the kmemcg flag has nothing to do with mapping to userspace. It only means that the page has been accounted by the page allocator, so it has to be properly uncharged on release. Some bpf maps are mapping the vmalloc-based memory to userspace, and their memory can't be accounted because of this implementation detail. This patchset removes this limitation by moving the PageKmemcg flag into one of the free bits of the page->mem_cgroup pointer. Also it formalizes accesses to the page->mem_cgroup and page->obj_cgroups using new helpers, adds several checks and removes a couple of obsolete functions. As the result the code became more robust with fewer open-coded bit tricks. This patch (of 4): Currently there are many open-coded reads of the page->mem_cgroup pointer, as well as a couple of read helpers, which are barely used. It creates an obstacle on a way to reuse some bits of the pointer for storing additional bits of information. In fact, we already do this for slab pages, where the last bit indicates that a pointer has an attached vector of objcg pointers instead of a regular memcg pointer. This commits uses 2 existing helpers and introduces a new helper to converts all read sides to calls of these helpers: struct mem_cgroup *page_memcg(struct page *page); struct mem_cgroup *page_memcg_rcu(struct page *page); struct mem_cgroup *page_memcg_check(struct page *page); page_memcg_check() is intended to be used in cases when the page can be a slab page and have a memcg pointer pointing at objcg vector. It does check the lowest bit, and if set, returns NULL. page_memcg() contains a VM_BUG_ON_PAGE() check for the page not being a slab page. To make sure nobody uses a direct access, struct page's mem_cgroup/obj_cgroups is converted to unsigned long memcg_data. Change-Id: I052ddf916e3033cc1acf934ac0b6eea551d61d00 Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com
179 lines
4.5 KiB
C
179 lines
4.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* mm/debug.c
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*
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* mm/ specific debug routines.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/trace_events.h>
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#include <linux/memcontrol.h>
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#include <trace/events/mmflags.h>
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#include <linux/migrate.h>
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#include <linux/page_owner.h>
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#include "internal.h"
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char *migrate_reason_names[MR_TYPES] = {
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"compaction",
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"memory_failure",
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"memory_hotplug",
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"syscall_or_cpuset",
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"mempolicy_mbind",
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"numa_misplaced",
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"cma",
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};
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const struct trace_print_flags pageflag_names[] = {
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__def_pageflag_names,
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{0, NULL}
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};
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const struct trace_print_flags gfpflag_names[] = {
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__def_gfpflag_names,
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{0, NULL}
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};
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const struct trace_print_flags vmaflag_names[] = {
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__def_vmaflag_names,
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{0, NULL}
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};
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void __dump_page(struct page *page, const char *reason)
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{
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bool page_poisoned = PagePoisoned(page);
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int mapcount;
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/*
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* If struct page is poisoned don't access Page*() functions as that
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* leads to recursive loop. Page*() check for poisoned pages, and calls
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* dump_page() when detected.
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*/
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if (page_poisoned) {
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pr_emerg("page:%px is uninitialized and poisoned", page);
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goto hex_only;
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}
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/*
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* Avoid VM_BUG_ON() in page_mapcount().
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* page->_mapcount space in struct page is used by sl[aou]b pages to
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* encode own info.
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*/
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mapcount = PageSlab(page) ? 0 : page_mapcount(page);
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pr_emerg("page:%px count:%d mapcount:%d mapping:%px index:%#lx",
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page, page_ref_count(page), mapcount,
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page->mapping, page_to_pgoff(page));
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if (PageCompound(page))
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pr_cont(" compound_mapcount: %d", compound_mapcount(page));
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pr_cont("\n");
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BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
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pr_emerg("flags: %#lx(%pGp)\n", page->flags, &page->flags);
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hex_only:
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print_hex_dump(KERN_ALERT, "raw: ", DUMP_PREFIX_NONE, 32,
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sizeof(unsigned long), page,
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sizeof(struct page), false);
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if (reason)
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pr_alert("page dumped because: %s\n", reason);
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#ifdef CONFIG_MEMCG
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if (!page_poisoned && page->memcg_data)
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pr_alert("page's memcg:%lx\n", page->memcg_data);
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#endif
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}
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void dump_page(struct page *page, const char *reason)
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{
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__dump_page(page, reason);
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dump_page_owner(page);
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}
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EXPORT_SYMBOL(dump_page);
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#ifdef CONFIG_DEBUG_VM
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void dump_vma(const struct vm_area_struct *vma)
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{
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pr_emerg("vma %px start %px end %px\n"
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"next %px prev %px mm %px\n"
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"prot %lx anon_vma %px vm_ops %px\n"
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"pgoff %lx file %px private_data %px\n"
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"flags: %#lx(%pGv)\n",
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vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_next,
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vma->vm_prev, vma->vm_mm,
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(unsigned long)pgprot_val(vma->vm_page_prot),
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vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
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vma->vm_file, vma->vm_private_data,
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vma->vm_flags, &vma->vm_flags);
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}
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EXPORT_SYMBOL(dump_vma);
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void dump_mm(const struct mm_struct *mm)
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{
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pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
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#ifdef CONFIG_MMU
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"get_unmapped_area %px\n"
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#endif
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"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
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"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
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"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
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"pinned_vm %lx data_vm %lx exec_vm %lx stack_vm %lx\n"
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"start_code %lx end_code %lx start_data %lx end_data %lx\n"
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"start_brk %lx brk %lx start_stack %lx\n"
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"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
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"binfmt %px flags %lx core_state %px\n"
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#ifdef CONFIG_AIO
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"ioctx_table %px\n"
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#endif
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#ifdef CONFIG_MEMCG
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"owner %px "
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#endif
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"exe_file %px\n"
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#ifdef CONFIG_MMU_NOTIFIER
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"mmu_notifier_mm %px\n"
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#endif
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#ifdef CONFIG_NUMA_BALANCING
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"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
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#endif
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"tlb_flush_pending %d\n"
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"def_flags: %#lx(%pGv)\n",
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mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
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#ifdef CONFIG_MMU
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mm->get_unmapped_area,
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#endif
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mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
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mm->pgd, atomic_read(&mm->mm_users),
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atomic_read(&mm->mm_count),
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mm_pgtables_bytes(mm),
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mm->map_count,
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mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
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mm->pinned_vm, mm->data_vm, mm->exec_vm, mm->stack_vm,
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mm->start_code, mm->end_code, mm->start_data, mm->end_data,
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mm->start_brk, mm->brk, mm->start_stack,
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mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
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mm->binfmt, mm->flags, mm->core_state,
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#ifdef CONFIG_AIO
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mm->ioctx_table,
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#endif
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#ifdef CONFIG_MEMCG
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mm->owner,
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#endif
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mm->exe_file,
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#ifdef CONFIG_MMU_NOTIFIER
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mm->mmu_notifier_mm,
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#endif
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#ifdef CONFIG_NUMA_BALANCING
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mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
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#endif
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atomic_read(&mm->tlb_flush_pending),
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mm->def_flags, &mm->def_flags
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);
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}
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#endif /* CONFIG_DEBUG_VM */
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