mm/debug.c - pub/scm/linux/kernel/git/mkl/linux-can - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * mm/debug.c
  *
  * mm/ specific debug routines.
  *
  */

 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/trace_events.h>
 #include <linux/memcontrol.h>
 #include <trace/events/mmflags.h>
 #include <linux/migrate.h>
 #include <linux/page_owner.h>
 #include <linux/ctype.h>

 #include "internal.h"
 #include <trace/events/migrate.h>

 /*
  * Define EM() and EMe() so that MIGRATE_REASON from trace/events/migrate.h can
  * be used to populate migrate_reason_names[].
  */
 #undef EM
 #undef EMe
 #define EM(a, b)	b,
 #define EMe(a, b)	b

 const char *migrate_reason_names[MR_TYPES] = {
 	MIGRATE_REASON
 };

 const struct trace_print_flags pageflag_names[] = {
 	__def_pageflag_names,
 	{0, NULL}
 };

 const struct trace_print_flags gfpflag_names[] = {
 	__def_gfpflag_names,
 	{0, NULL}
 };

 const struct trace_print_flags vmaflag_names[] = {
 	__def_vmaflag_names,
 	{0, NULL}
 };

 #define DEF_PAGETYPE_NAME(_name) [PGTY_##_name - 0xf0] =  __stringify(_name)

 static const char *page_type_names[] = {
 	DEF_PAGETYPE_NAME(slab),
 	DEF_PAGETYPE_NAME(hugetlb),
 	DEF_PAGETYPE_NAME(offline),
 	DEF_PAGETYPE_NAME(guard),
 	DEF_PAGETYPE_NAME(table),
 	DEF_PAGETYPE_NAME(buddy),
 	DEF_PAGETYPE_NAME(unaccepted),
 };

 static const char *page_type_name(unsigned int page_type)
 {
 	unsigned i = (page_type >> 24) - 0xf0;

 	if (i >= ARRAY_SIZE(page_type_names))
 		return "unknown";
 	return page_type_names[i];
 }

 static void __dump_folio(struct folio *folio, struct page *page,
 		unsigned long pfn, unsigned long idx)
 {
 	struct address_space *mapping = folio_mapping(folio);
 	int mapcount = atomic_read(&page->_mapcount) + 1;
 	char *type = "";

 	if (page_mapcount_is_type(mapcount))
 		mapcount = 0;

 	pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
 			folio_ref_count(folio), mapcount, mapping,
 			folio->index + idx, pfn);
 	if (folio_test_large(folio)) {
 		int pincount = 0;

 		if (folio_has_pincount(folio))
 			pincount = atomic_read(&folio->_pincount);

 		pr_warn("head: order:%u mapcount:%d entire_mapcount:%d nr_pages_mapped:%d pincount:%d\n",
 				folio_order(folio),
 				folio_mapcount(folio),
 				folio_entire_mapcount(folio),
 				folio_nr_pages_mapped(folio),
 				pincount);
 	}

 #ifdef CONFIG_MEMCG
 	if (folio->memcg_data)
 		pr_warn("memcg:%lx\n", folio->memcg_data);
 #endif
 	if (folio_test_ksm(folio))
 		type = "ksm ";
 	else if (folio_test_anon(folio))
 		type = "anon ";
 	else if (mapping)
 		dump_mapping(mapping);
 	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

 	/*
 	 * Accessing the pageblock without the zone lock. It could change to
 	 * "isolate" again in the meantime, but since we are just dumping the
 	 * state for debugging, it should be fine to accept a bit of
 	 * inaccuracy here due to racing.
 	 */
 	pr_warn("%sflags: %pGp%s\n", type, &folio->flags,
 		is_migrate_cma_folio(folio, pfn) ? " CMA" : "");
 	if (page_has_type(&folio->page))
 		pr_warn("page_type: %x(%s)\n", folio->page.page_type >> 24,
 				page_type_name(folio->page.page_type));

 	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
 			sizeof(unsigned long), page,
 			sizeof(struct page), false);
 	if (folio_test_large(folio))
 		print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
 			sizeof(unsigned long), folio,
 			2 * sizeof(struct page), false);
 }

 static void __dump_page(const struct page *page)
 {
 	struct page_snapshot ps;

 	snapshot_page(&ps, page);
 	if (!snapshot_page_is_faithful(&ps))
 		pr_warn("page does not match folio\n");

 	__dump_folio(&ps.folio_snapshot, &ps.page_snapshot, ps.pfn, ps.idx);
 }

 void dump_page(const struct page *page, const char *reason)
 {
 	if (PagePoisoned(page))
 		pr_warn("page:%p is uninitialized and poisoned\n", page);
 	else
 		__dump_page(page);
 	if (reason)
 		pr_warn("page dumped because: %s\n", reason);
 	dump_page_owner(page);
 }
 EXPORT_SYMBOL(dump_page);

 #ifdef CONFIG_DEBUG_VM

 void dump_vma(const struct vm_area_struct *vma)
 {
 	pr_emerg("vma %px start %px end %px mm %px\n"
 		"prot %lx anon_vma %px vm_ops %px\n"
 		"pgoff %lx file %px private_data %px\n"
 #ifdef CONFIG_PER_VMA_LOCK
 		"refcnt %x\n"
 #endif
 		"flags: %#lx(%pGv)\n",
 		vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_mm,
 		(unsigned long)pgprot_val(vma->vm_page_prot),
 		vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
 		vma->vm_file, vma->vm_private_data,
 #ifdef CONFIG_PER_VMA_LOCK
 		refcount_read(&vma->vm_refcnt),
 #endif
 		vma->vm_flags, &vma->vm_flags);
 }
 EXPORT_SYMBOL(dump_vma);

 void dump_mm(const struct mm_struct *mm)
 {
 	pr_emerg("mm %px task_size %lu\n"
 		"mmap_base %lu mmap_legacy_base %lu\n"
 		"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
 		"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
 		"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
 		"start_code %lx end_code %lx start_data %lx end_data %lx\n"
 		"start_brk %lx brk %lx start_stack %lx\n"
 		"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
 		"binfmt %px flags %*pb\n"
 #ifdef CONFIG_AIO
 		"ioctx_table %px\n"
 #endif
 #ifdef CONFIG_MEMCG
 		"owner %px "
 #endif
 		"exe_file %px\n"
 #ifdef CONFIG_MMU_NOTIFIER
 		"notifier_subscriptions %px\n"
 #endif
 #ifdef CONFIG_NUMA_BALANCING
 		"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
 #endif
 		"tlb_flush_pending %d\n"
 		"def_flags: %#lx(%pGv)\n",

 		mm, mm->task_size,
 		mm->mmap_base, mm->mmap_legacy_base,
 		mm->pgd, atomic_read(&mm->mm_users),
 		atomic_read(&mm->mm_count),
 		mm_pgtables_bytes(mm),
 		mm->map_count,
 		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
 		(u64)atomic64_read(&mm->pinned_vm),
 		mm->data_vm, mm->exec_vm, mm->stack_vm,
 		mm->start_code, mm->end_code, mm->start_data, mm->end_data,
 		mm->start_brk, mm->brk, mm->start_stack,
 		mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
 		mm->binfmt, NUM_MM_FLAG_BITS, __mm_flags_get_bitmap(mm),
 #ifdef CONFIG_AIO
 		mm->ioctx_table,
 #endif
 #ifdef CONFIG_MEMCG
 		mm->owner,
 #endif
 		mm->exe_file,
 #ifdef CONFIG_MMU_NOTIFIER
 		mm->notifier_subscriptions,
 #endif
 #ifdef CONFIG_NUMA_BALANCING
 		mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
 #endif
 		atomic_read(&mm->tlb_flush_pending),
 		mm->def_flags, &mm->def_flags
 	);
 }
 EXPORT_SYMBOL(dump_mm);

 void dump_vmg(const struct vma_merge_struct *vmg, const char *reason)
 {
 	if (reason)
 		pr_warn("vmg %px dumped because: %s\n", vmg, reason);

 	if (!vmg) {
 		pr_warn("vmg %px state: (NULL)\n", vmg);
 		return;
 	}

 	pr_warn("vmg %px state: mm %px pgoff %lx\n"
 		"vmi %px [%lx,%lx)\n"
 		"prev %px middle %px next %px target %px\n"
 		"start %lx end %lx flags %lx\n"
 		"file %px anon_vma %px policy %px\n"
 		"uffd_ctx %px\n"
 		"anon_name %px\n"
 		"state %x\n"
 		"just_expand %d\n"
 		"__adjust_middle_start %d __adjust_next_start %d\n"
 		"__remove_middle %d __remove_next %d\n",
 		vmg, vmg->mm, vmg->pgoff,
 		vmg->vmi, vmg->vmi ? vma_iter_addr(vmg->vmi) : 0,
 		vmg->vmi ? vma_iter_end(vmg->vmi) : 0,
 		vmg->prev, vmg->middle, vmg->next, vmg->target,
 		vmg->start, vmg->end, vmg->vm_flags,
 		vmg->file, vmg->anon_vma, vmg->policy,
 #ifdef CONFIG_USERFAULTFD
 		vmg->uffd_ctx.ctx,
 #else
 		(void *)0,
 #endif
 		vmg->anon_name,
 		(int)vmg->state,
 		vmg->just_expand,
 		vmg->__adjust_middle_start, vmg->__adjust_next_start,
 		vmg->__remove_middle, vmg->__remove_next);

 	if (vmg->mm) {
 		pr_warn("vmg %px mm:\n", vmg);
 		dump_mm(vmg->mm);
 	} else {
 		pr_warn("vmg %px mm: (NULL)\n", vmg);
 	}

 	if (vmg->prev) {
 		pr_warn("vmg %px prev:\n", vmg);
 		dump_vma(vmg->prev);
 	} else {
 		pr_warn("vmg %px prev: (NULL)\n", vmg);
 	}

 	if (vmg->middle) {
 		pr_warn("vmg %px middle:\n", vmg);
 		dump_vma(vmg->middle);
 	} else {
 		pr_warn("vmg %px middle: (NULL)\n", vmg);
 	}

 	if (vmg->next) {
 		pr_warn("vmg %px next:\n", vmg);
 		dump_vma(vmg->next);
 	} else {
 		pr_warn("vmg %px next: (NULL)\n", vmg);
 	}

 #ifdef CONFIG_DEBUG_VM_MAPLE_TREE
 	if (vmg->vmi) {
 		pr_warn("vmg %px vmi:\n", vmg);
 		vma_iter_dump_tree(vmg->vmi);
 	} else {
 		pr_warn("vmg %px vmi: (NULL)\n", vmg);
 	}
 #endif
 }
 EXPORT_SYMBOL(dump_vmg);

 static bool page_init_poisoning __read_mostly = true;

 static int __init setup_vm_debug(char *str)
 {
 	bool __page_init_poisoning = true;

 	/*
 	 * Calling vm_debug with no arguments is equivalent to requesting
 	 * to enable all debugging options we can control.
 	 */
 	if (*str++ != '=' || !*str)
 		goto out;

 	__page_init_poisoning = false;
 	if (*str == '-')
 		goto out;

 	while (*str) {
 		switch (tolower(*str)) {
 		case'p':
 			__page_init_poisoning = true;
 			break;
 		default:
 			pr_err("vm_debug option '%c' unknown. skipped\n",
 			       *str);
 		}

 		str++;
 	}
 out:
 	if (page_init_poisoning && !__page_init_poisoning)
 		pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");

 	page_init_poisoning = __page_init_poisoning;

 	return 1;
 }
 __setup("vm_debug", setup_vm_debug);

 void page_init_poison(struct page *page, size_t size)
 {
 	if (page_init_poisoning)
 		memset(page, PAGE_POISON_PATTERN, size);
 }

 void vma_iter_dump_tree(const struct vma_iterator *vmi)
 {
 #if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
 	mas_dump(&vmi->mas);
 	mt_dump(vmi->mas.tree, mt_dump_hex);
 #endif	/* CONFIG_DEBUG_VM_MAPLE_TREE */
 }

 #endif		/* CONFIG_DEBUG_VM */
	// SPDX-License-Identifier: GPL-2.0
	/*
	* mm/debug.c
	*
	* mm/ specific debug routines.
	*
	*/

	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/trace_events.h>
	#include <linux/memcontrol.h>
	#include <trace/events/mmflags.h>
	#include <linux/migrate.h>
	#include <linux/page_owner.h>
	#include <linux/ctype.h>

	#include "internal.h"
	#include <trace/events/migrate.h>

	/*
	* Define EM() and EMe() so that MIGRATE_REASON from trace/events/migrate.h can
	* be used to populate migrate_reason_names[].
	*/
	#undef EM
	#undef EMe
	#define EM(a, b) b,
	#define EMe(a, b) b

	const char *migrate_reason_names[MR_TYPES] = {
	MIGRATE_REASON
	};

	const struct trace_print_flags pageflag_names[] = {
	__def_pageflag_names,
	{0, NULL}
	};

	const struct trace_print_flags gfpflag_names[] = {
	__def_gfpflag_names,
	{0, NULL}
	};

	const struct trace_print_flags vmaflag_names[] = {
	__def_vmaflag_names,
	{0, NULL}
	};

	#define DEF_PAGETYPE_NAME(_name) [PGTY_##_name - 0xf0] = __stringify(_name)

	static const char *page_type_names[] = {
	DEF_PAGETYPE_NAME(slab),
	DEF_PAGETYPE_NAME(hugetlb),
	DEF_PAGETYPE_NAME(offline),
	DEF_PAGETYPE_NAME(guard),
	DEF_PAGETYPE_NAME(table),
	DEF_PAGETYPE_NAME(buddy),
	DEF_PAGETYPE_NAME(unaccepted),
	};

	static const char *page_type_name(unsigned int page_type)
	{
	unsigned i = (page_type >> 24) - 0xf0;

	if (i >= ARRAY_SIZE(page_type_names))
	return "unknown";
	return page_type_names[i];
	}

	static void __dump_folio(struct folio folio, struct page page,
	unsigned long pfn, unsigned long idx)
	{
	struct address_space *mapping = folio_mapping(folio);
	int mapcount = atomic_read(&page->_mapcount) + 1;
	char *type = "";

	if (page_mapcount_is_type(mapcount))
	mapcount = 0;

	pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
	folio_ref_count(folio), mapcount, mapping,
	folio->index + idx, pfn);
	if (folio_test_large(folio)) {
	int pincount = 0;

	if (folio_has_pincount(folio))
	pincount = atomic_read(&folio->_pincount);

	pr_warn("head: order:%u mapcount:%d entire_mapcount:%d nr_pages_mapped:%d pincount:%d\n",
	folio_order(folio),
	folio_mapcount(folio),
	folio_entire_mapcount(folio),
	folio_nr_pages_mapped(folio),
	pincount);
	}

	#ifdef CONFIG_MEMCG
	if (folio->memcg_data)
	pr_warn("memcg:%lx\n", folio->memcg_data);
	#endif
	if (folio_test_ksm(folio))
	type = "ksm ";
	else if (folio_test_anon(folio))
	type = "anon ";
	else if (mapping)
	dump_mapping(mapping);
	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

	/*
	* Accessing the pageblock without the zone lock. It could change to
	* "isolate" again in the meantime, but since we are just dumping the
	* state for debugging, it should be fine to accept a bit of
	* inaccuracy here due to racing.
	*/
	pr_warn("%sflags: %pGp%s\n", type, &folio->flags,
	is_migrate_cma_folio(folio, pfn) ? " CMA" : "");
	if (page_has_type(&folio->page))
	pr_warn("page_type: %x(%s)\n", folio->page.page_type >> 24,
	page_type_name(folio->page.page_type));

	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
	sizeof(unsigned long), page,
	sizeof(struct page), false);
	if (folio_test_large(folio))
	print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
	sizeof(unsigned long), folio,
	2 * sizeof(struct page), false);
	}

	static void __dump_page(const struct page *page)
	{
	struct page_snapshot ps;

	snapshot_page(&ps, page);
	if (!snapshot_page_is_faithful(&ps))
	pr_warn("page does not match folio\n");

	__dump_folio(&ps.folio_snapshot, &ps.page_snapshot, ps.pfn, ps.idx);
	}

	void dump_page(const struct page page, const char reason)
	{
	if (PagePoisoned(page))
	pr_warn("page:%p is uninitialized and poisoned\n", page);
	else
	__dump_page(page);
	if (reason)
	pr_warn("page dumped because: %s\n", reason);
	dump_page_owner(page);
	}
	EXPORT_SYMBOL(dump_page);

	#ifdef CONFIG_DEBUG_VM

	void dump_vma(const struct vm_area_struct *vma)
	{
	pr_emerg("vma %px start %px end %px mm %px\n"
	"prot %lx anon_vma %px vm_ops %px\n"
	"pgoff %lx file %px private_data %px\n"
	#ifdef CONFIG_PER_VMA_LOCK
	"refcnt %x\n"
	#endif
	"flags: %#lx(%pGv)\n",
	vma, (void )vma->vm_start, (void )vma->vm_end, vma->vm_mm,
	(unsigned long)pgprot_val(vma->vm_page_prot),
	vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
	vma->vm_file, vma->vm_private_data,
	#ifdef CONFIG_PER_VMA_LOCK
	refcount_read(&vma->vm_refcnt),
	#endif
	vma->vm_flags, &vma->vm_flags);
	}
	EXPORT_SYMBOL(dump_vma);

	void dump_mm(const struct mm_struct *mm)
	{
	pr_emerg("mm %px task_size %lu\n"
	"mmap_base %lu mmap_legacy_base %lu\n"
	"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
	"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
	"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
	"start_code %lx end_code %lx start_data %lx end_data %lx\n"
	"start_brk %lx brk %lx start_stack %lx\n"
	"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
	"binfmt %px flags %*pb\n"
	#ifdef CONFIG_AIO
	"ioctx_table %px\n"
	#endif
	#ifdef CONFIG_MEMCG
	"owner %px "
	#endif
	"exe_file %px\n"
	#ifdef CONFIG_MMU_NOTIFIER
	"notifier_subscriptions %px\n"
	#endif
	#ifdef CONFIG_NUMA_BALANCING
	"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
	#endif
	"tlb_flush_pending %d\n"
	"def_flags: %#lx(%pGv)\n",

	mm, mm->task_size,
	mm->mmap_base, mm->mmap_legacy_base,
	mm->pgd, atomic_read(&mm->mm_users),
	atomic_read(&mm->mm_count),
	mm_pgtables_bytes(mm),
	mm->map_count,
	mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
	(u64)atomic64_read(&mm->pinned_vm),
	mm->data_vm, mm->exec_vm, mm->stack_vm,
	mm->start_code, mm->end_code, mm->start_data, mm->end_data,
	mm->start_brk, mm->brk, mm->start_stack,
	mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
	mm->binfmt, NUM_MM_FLAG_BITS, __mm_flags_get_bitmap(mm),
	#ifdef CONFIG_AIO
	mm->ioctx_table,
	#endif
	#ifdef CONFIG_MEMCG
	mm->owner,
	#endif
	mm->exe_file,
	#ifdef CONFIG_MMU_NOTIFIER
	mm->notifier_subscriptions,
	#endif
	#ifdef CONFIG_NUMA_BALANCING
	mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
	#endif
	atomic_read(&mm->tlb_flush_pending),
	mm->def_flags, &mm->def_flags
	);
	}
	EXPORT_SYMBOL(dump_mm);

	void dump_vmg(const struct vma_merge_struct vmg, const char reason)
	{
	if (reason)
	pr_warn("vmg %px dumped because: %s\n", vmg, reason);

	if (!vmg) {
	pr_warn("vmg %px state: (NULL)\n", vmg);
	return;
	}

	pr_warn("vmg %px state: mm %px pgoff %lx\n"
	"vmi %px [%lx,%lx)\n"
	"prev %px middle %px next %px target %px\n"
	"start %lx end %lx flags %lx\n"
	"file %px anon_vma %px policy %px\n"
	"uffd_ctx %px\n"
	"anon_name %px\n"
	"state %x\n"
	"just_expand %d\n"
	"__adjust_middle_start %d __adjust_next_start %d\n"
	"__remove_middle %d __remove_next %d\n",
	vmg, vmg->mm, vmg->pgoff,
	vmg->vmi, vmg->vmi ? vma_iter_addr(vmg->vmi) : 0,
	vmg->vmi ? vma_iter_end(vmg->vmi) : 0,
	vmg->prev, vmg->middle, vmg->next, vmg->target,
	vmg->start, vmg->end, vmg->vm_flags,
	vmg->file, vmg->anon_vma, vmg->policy,
	#ifdef CONFIG_USERFAULTFD
	vmg->uffd_ctx.ctx,
	#else
	(void *)0,
	#endif
	vmg->anon_name,
	(int)vmg->state,
	vmg->just_expand,
	vmg->__adjust_middle_start, vmg->__adjust_next_start,
	vmg->__remove_middle, vmg->__remove_next);

	if (vmg->mm) {
	pr_warn("vmg %px mm:\n", vmg);
	dump_mm(vmg->mm);
	} else {
	pr_warn("vmg %px mm: (NULL)\n", vmg);
	}

	if (vmg->prev) {
	pr_warn("vmg %px prev:\n", vmg);
	dump_vma(vmg->prev);
	} else {
	pr_warn("vmg %px prev: (NULL)\n", vmg);
	}

	if (vmg->middle) {
	pr_warn("vmg %px middle:\n", vmg);
	dump_vma(vmg->middle);
	} else {
	pr_warn("vmg %px middle: (NULL)\n", vmg);
	}

	if (vmg->next) {
	pr_warn("vmg %px next:\n", vmg);
	dump_vma(vmg->next);
	} else {
	pr_warn("vmg %px next: (NULL)\n", vmg);
	}

	#ifdef CONFIG_DEBUG_VM_MAPLE_TREE
	if (vmg->vmi) {
	pr_warn("vmg %px vmi:\n", vmg);
	vma_iter_dump_tree(vmg->vmi);
	} else {
	pr_warn("vmg %px vmi: (NULL)\n", vmg);
	}
	#endif
	}
	EXPORT_SYMBOL(dump_vmg);

	static bool page_init_poisoning __read_mostly = true;

	static int __init setup_vm_debug(char *str)
	{
	bool __page_init_poisoning = true;

	/*
	* Calling vm_debug with no arguments is equivalent to requesting
	* to enable all debugging options we can control.
	*/
	if (str++ != '=' \|\| !str)
	goto out;

	__page_init_poisoning = false;
	if (*str == '-')
	goto out;

	while (*str) {
	switch (tolower(*str)) {
	case'p':
	__page_init_poisoning = true;
	break;
	default:
	pr_err("vm_debug option '%c' unknown. skipped\n",
	*str);
	}

	str++;
	}
	out:
	if (page_init_poisoning && !__page_init_poisoning)
	pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");

	page_init_poisoning = __page_init_poisoning;

	return 1;
	}
	__setup("vm_debug", setup_vm_debug);

	void page_init_poison(struct page *page, size_t size)
	{
	if (page_init_poisoning)
	memset(page, PAGE_POISON_PATTERN, size);
	}

	void vma_iter_dump_tree(const struct vma_iterator *vmi)
	{
	#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
	mas_dump(&vmi->mas);
	mt_dump(vmi->mas.tree, mt_dump_hex);
	#endif /* CONFIG_DEBUG_VM_MAPLE_TREE */
	}

	#endif /* CONFIG_DEBUG_VM */