forked from Minki/linux
1d798ca3f1
Hugh has pointed that compound_head() call can be unsafe in some
context. There's one example:
CPU0 CPU1
isolate_migratepages_block()
page_count()
compound_head()
!!PageTail() == true
put_page()
tail->first_page = NULL
head = tail->first_page
alloc_pages(__GFP_COMP)
prep_compound_page()
tail->first_page = head
__SetPageTail(p);
!!PageTail() == true
<head == NULL dereferencing>
The race is pure theoretical. I don't it's possible to trigger it in
practice. But who knows.
We can fix the race by changing how encode PageTail() and compound_head()
within struct page to be able to update them in one shot.
The patch introduces page->compound_head into third double word block in
front of compound_dtor and compound_order. Bit 0 encodes PageTail() and
the rest bits are pointer to head page if bit zero is set.
The patch moves page->pmd_huge_pte out of word, just in case if an
architecture defines pgtable_t into something what can have the bit 0
set.
hugetlb_cgroup uses page->lru.next in the second tail page to store
pointer struct hugetlb_cgroup. The patch switch it to use page->private
in the second tail page instead. The space is free since ->first_page is
removed from the union.
The patch also opens possibility to remove HUGETLB_CGROUP_MIN_ORDER
limitation, since there's now space in first tail page to store struct
hugetlb_cgroup pointer. But that's out of scope of the patch.
That means page->compound_head shares storage space with:
- page->lru.next;
- page->next;
- page->rcu_head.next;
That's too long list to be absolutely sure, but looks like nobody uses
bit 0 of the word.
page->rcu_head.next guaranteed[1] to have bit 0 clean as long as we use
call_rcu(), call_rcu_bh(), call_rcu_sched(), or call_srcu(). But future
call_rcu_lazy() is not allowed as it makes use of the bit and we can
get false positive PageTail().
[1] http://lkml.kernel.org/g/20150827163634.GD4029@linux.vnet.ibm.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
241 lines
6.6 KiB
C
241 lines
6.6 KiB
C
/*
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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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static const struct trace_print_flags pageflag_names[] = {
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{1UL << PG_locked, "locked" },
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{1UL << PG_error, "error" },
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{1UL << PG_referenced, "referenced" },
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{1UL << PG_uptodate, "uptodate" },
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{1UL << PG_dirty, "dirty" },
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{1UL << PG_lru, "lru" },
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{1UL << PG_active, "active" },
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{1UL << PG_slab, "slab" },
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{1UL << PG_owner_priv_1, "owner_priv_1" },
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{1UL << PG_arch_1, "arch_1" },
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{1UL << PG_reserved, "reserved" },
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{1UL << PG_private, "private" },
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{1UL << PG_private_2, "private_2" },
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{1UL << PG_writeback, "writeback" },
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{1UL << PG_head, "head" },
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{1UL << PG_swapcache, "swapcache" },
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{1UL << PG_mappedtodisk, "mappedtodisk" },
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{1UL << PG_reclaim, "reclaim" },
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{1UL << PG_swapbacked, "swapbacked" },
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{1UL << PG_unevictable, "unevictable" },
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#ifdef CONFIG_MMU
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{1UL << PG_mlocked, "mlocked" },
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#endif
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#ifdef CONFIG_ARCH_USES_PG_UNCACHED
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{1UL << PG_uncached, "uncached" },
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#endif
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#ifdef CONFIG_MEMORY_FAILURE
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{1UL << PG_hwpoison, "hwpoison" },
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#endif
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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{1UL << PG_compound_lock, "compound_lock" },
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#endif
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#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
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{1UL << PG_young, "young" },
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{1UL << PG_idle, "idle" },
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#endif
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};
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static void dump_flags(unsigned long flags,
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const struct trace_print_flags *names, int count)
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{
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const char *delim = "";
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unsigned long mask;
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int i;
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pr_emerg("flags: %#lx(", flags);
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/* remove zone id */
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flags &= (1UL << NR_PAGEFLAGS) - 1;
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for (i = 0; i < count && flags; i++) {
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mask = names[i].mask;
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if ((flags & mask) != mask)
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continue;
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flags &= ~mask;
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pr_cont("%s%s", delim, names[i].name);
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delim = "|";
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}
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/* check for left over flags */
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if (flags)
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pr_cont("%s%#lx", delim, flags);
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pr_cont(")\n");
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}
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void dump_page_badflags(struct page *page, const char *reason,
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unsigned long badflags)
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{
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pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
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page, atomic_read(&page->_count), page_mapcount(page),
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page->mapping, page->index);
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BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS);
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dump_flags(page->flags, pageflag_names, ARRAY_SIZE(pageflag_names));
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if (reason)
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pr_alert("page dumped because: %s\n", reason);
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if (page->flags & badflags) {
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pr_alert("bad because of flags:\n");
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dump_flags(page->flags & badflags,
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pageflag_names, ARRAY_SIZE(pageflag_names));
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}
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#ifdef CONFIG_MEMCG
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if (page->mem_cgroup)
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pr_alert("page->mem_cgroup:%p\n", page->mem_cgroup);
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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_badflags(page, reason, 0);
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}
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EXPORT_SYMBOL(dump_page);
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#ifdef CONFIG_DEBUG_VM
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static const struct trace_print_flags vmaflags_names[] = {
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{VM_READ, "read" },
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{VM_WRITE, "write" },
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{VM_EXEC, "exec" },
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{VM_SHARED, "shared" },
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{VM_MAYREAD, "mayread" },
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{VM_MAYWRITE, "maywrite" },
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{VM_MAYEXEC, "mayexec" },
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{VM_MAYSHARE, "mayshare" },
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{VM_GROWSDOWN, "growsdown" },
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{VM_PFNMAP, "pfnmap" },
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{VM_DENYWRITE, "denywrite" },
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{VM_LOCKONFAULT, "lockonfault" },
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{VM_LOCKED, "locked" },
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{VM_IO, "io" },
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{VM_SEQ_READ, "seqread" },
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{VM_RAND_READ, "randread" },
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{VM_DONTCOPY, "dontcopy" },
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{VM_DONTEXPAND, "dontexpand" },
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{VM_ACCOUNT, "account" },
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{VM_NORESERVE, "noreserve" },
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{VM_HUGETLB, "hugetlb" },
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#if defined(CONFIG_X86)
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{VM_PAT, "pat" },
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#elif defined(CONFIG_PPC)
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{VM_SAO, "sao" },
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#elif defined(CONFIG_PARISC) || defined(CONFIG_METAG) || defined(CONFIG_IA64)
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{VM_GROWSUP, "growsup" },
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#elif !defined(CONFIG_MMU)
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{VM_MAPPED_COPY, "mappedcopy" },
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#else
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{VM_ARCH_1, "arch_1" },
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#endif
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{VM_DONTDUMP, "dontdump" },
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#ifdef CONFIG_MEM_SOFT_DIRTY
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{VM_SOFTDIRTY, "softdirty" },
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#endif
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{VM_MIXEDMAP, "mixedmap" },
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{VM_HUGEPAGE, "hugepage" },
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{VM_NOHUGEPAGE, "nohugepage" },
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{VM_MERGEABLE, "mergeable" },
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};
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void dump_vma(const struct vm_area_struct *vma)
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{
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pr_emerg("vma %p start %p end %p\n"
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"next %p prev %p mm %p\n"
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"prot %lx anon_vma %p vm_ops %p\n"
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"pgoff %lx file %p private_data %p\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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dump_flags(vma->vm_flags, vmaflags_names, ARRAY_SIZE(vmaflags_names));
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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 %p mmap %p seqnum %d task_size %lu\n"
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#ifdef CONFIG_MMU
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"get_unmapped_area %p\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 %p mm_users %d mm_count %d nr_ptes %lu nr_pmds %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 shared_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 %p flags %lx core_state %p\n"
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#ifdef CONFIG_AIO
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"ioctx_table %p\n"
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#endif
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#ifdef CONFIG_MEMCG
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"owner %p "
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#endif
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"exe_file %p\n"
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#ifdef CONFIG_MMU_NOTIFIER
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"mmu_notifier_mm %p\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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#if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
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"tlb_flush_pending %d\n"
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#endif
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"%s", /* This is here to hold the comma */
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mm, mm->mmap, 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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atomic_long_read((atomic_long_t *)&mm->nr_ptes),
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mm_nr_pmds((struct mm_struct *)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->shared_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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#if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
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mm->tlb_flush_pending,
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#endif
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"" /* This is here to not have a comma! */
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);
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dump_flags(mm->def_flags, vmaflags_names,
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ARRAY_SIZE(vmaflags_names));
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}
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#endif /* CONFIG_DEBUG_VM */
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