[linux-block.git] / mm / debug.c

// 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"

const char *migrate_reason_names[MR_TYPES] = {
	"compaction",
	"memory_failure",
	"memory_hotplug",
	"syscall_or_cpuset",
	"mempolicy_mbind",
	"numa_misplaced",
	"cma",
};

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}
};

void __dump_page(struct page *page, const char *reason)
{
	struct page *head = compound_head(page);
	struct address_space *mapping;
	bool page_poisoned = PagePoisoned(page);
	bool compound = PageCompound(page);
	/*
	 * 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.
	 */
	bool page_cma = is_migrate_cma_page(page);
	int mapcount;
	char *type = "";

	/*
	 * If struct page is poisoned don't access Page*() functions as that
	 * leads to recursive loop. Page*() check for poisoned pages, and calls
	 * dump_page() when detected.
	 */
	if (page_poisoned) {
		pr_warn("page:%px is uninitialized and poisoned", page);
		goto hex_only;
	}

	if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
		/*
		 * Corrupt page, so we cannot call page_mapping. Instead, do a
		 * safe subset of the steps that page_mapping() does. Caution:
		 * this will be misleading for tail pages, PageSwapCache pages,
		 * and potentially other situations. (See the page_mapping()
		 * implementation for what's missing here.)
		 */
		unsigned long tmp = (unsigned long)page->mapping;

		if (tmp & PAGE_MAPPING_ANON)
			mapping = NULL;
		else
			mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
		head = page;
		compound = false;
	} else {
		mapping = page_mapping(page);
	}

	/*
	 * Avoid VM_BUG_ON() in page_mapcount().
	 * page->_mapcount space in struct page is used by sl[aou]b pages to
	 * encode own info.
	 */
	mapcount = PageSlab(head) ? 0 : page_mapcount(page);

	pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
			page, page_ref_count(head), mapcount, mapping,
			page_to_pgoff(page), page_to_pfn(page));
	if (compound) {
		if (hpage_pincount_available(page)) {
			pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
					head, compound_order(head),
					head_mapcount(head),
					head_pincount(head));
		} else {
			pr_warn("head:%p order:%u compound_mapcount:%d\n",
					head, compound_order(head),
					head_mapcount(head));
		}
	}
	if (PageKsm(page))
		type = "ksm ";
	else if (PageAnon(page))
		type = "anon ";
	else if (mapping) {
		struct inode *host;
		const struct address_space_operations *a_ops;
		struct hlist_node *dentry_first;
		struct dentry *dentry_ptr;
		struct dentry dentry;

		/*
		 * mapping can be invalid pointer and we don't want to crash
		 * accessing it, so probe everything depending on it carefully
		 */
		if (get_kernel_nofault(host, &mapping->host) ||
		    get_kernel_nofault(a_ops, &mapping->a_ops)) {
			pr_warn("failed to read mapping contents, not a valid kernel address?\n");
			goto out_mapping;
		}

		if (!host) {
			pr_warn("aops:%ps\n", a_ops);
			goto out_mapping;
		}

		if (get_kernel_nofault(dentry_first, &host->i_dentry.first)) {
			pr_warn("aops:%ps with invalid host inode %px\n",
					a_ops, host);
			goto out_mapping;
		}

		if (!dentry_first) {
			pr_warn("aops:%ps ino:%lx\n", a_ops, host->i_ino);
			goto out_mapping;
		}

		dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
		if (get_kernel_nofault(dentry, dentry_ptr)) {
			pr_warn("aops:%ps with invalid dentry %px\n", a_ops,
					dentry_ptr);
		} else {
			/*
			 * if dentry is corrupted, the %pd handler may still
			 * crash, but it's unlikely that we reach here with a
			 * corrupted struct page
			 */
			pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n",
					a_ops, host->i_ino, &dentry);
		}
	}
out_mapping:
	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);

	pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
		page_cma ? " CMA" : "");

hex_only:
	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
			sizeof(unsigned long), page,
			sizeof(struct page), false);
	if (head != page)
		print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
			sizeof(unsigned long), head,
			sizeof(struct page), false);

	if (reason)
		pr_warn("page dumped because: %s\n", reason);

#ifdef CONFIG_MEMCG
	if (!page_poisoned && page->mem_cgroup)
		pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup);
#endif
}

void dump_page(struct page *page, const char *reason)
{
	__dump_page(page, 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\n"
		"next %px prev %px mm %px\n"
		"prot %lx anon_vma %px vm_ops %px\n"
		"pgoff %lx file %px private_data %px\n"
		"flags: %#lx(%pGv)\n",
		vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_next,
		vma->vm_prev, 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,
		vma->vm_flags, &vma->vm_flags);
}
EXPORT_SYMBOL(dump_vma);

void dump_mm(const struct mm_struct *mm)
{
	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
#ifdef CONFIG_MMU
		"get_unmapped_area %px\n"
#endif
		"mmap_base %lu mmap_legacy_base %lu highest_vm_end %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 %lx core_state %px\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->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
#ifdef CONFIG_MMU
		mm->get_unmapped_area,
#endif
		mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
		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, mm->flags, mm->core_state,
#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
	);
}

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);
}
EXPORT_SYMBOL_GPL(page_init_poison);
#endif		/* CONFIG_DEBUG_VM */
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
31c9afa6 SL	2	/*
	3	* mm/debug.c
	4	*
	5	* mm/ specific debug routines.
	6	*
	7	*/
	8
82742a3a SL	9	#include <linux/kernel.h>
82742a3a SL	10	#include <linux/mm.h>
af658dca	11	#include <linux/trace_events.h>
82742a3a	12	#include <linux/memcontrol.h>
420adbe9	13	#include <trace/events/mmflags.h>
7cd12b4a	14	#include <linux/migrate.h>
4e462112	15	#include <linux/page_owner.h>
f682a97a	16	#include <linux/ctype.h>
82742a3a	17
edf14cdb VB	18	#include "internal.h"
edf14cdb VB	19
9a2f45ff	20	const char *migrate_reason_names[MR_TYPES] = {
7cd12b4a VB	21	"compaction",
	22	"memory_failure",
	23	"memory_hotplug",
	24	"syscall_or_cpuset",
	25	"mempolicy_mbind",
	26	"numa_misplaced",
	27	"cma",
	28	};
	29
edf14cdb VB	30	const struct trace_print_flags pageflag_names[] = {
	31	__def_pageflag_names,
	32	{0, NULL}
	33	};
	34
	35	const struct trace_print_flags gfpflag_names[] = {
	36	__def_gfpflag_names,
	37	{0, NULL}
420adbe9 VB	38	};
420adbe9 VB	39
edf14cdb VB	40	const struct trace_print_flags vmaflag_names[] = {
	41	__def_vmaflag_names,
	42	{0, NULL}
82742a3a SL	43	};
82742a3a SL	44
ff8e8116	45	void __dump_page(struct page page, const char reason)
82742a3a	46	{
6197ab98	47	struct page *head = compound_head(page);
311ade0e	48	struct address_space *mapping;
fc36def9	49	bool page_poisoned = PagePoisoned(page);
6197ab98	50	bool compound = PageCompound(page);
4a55c047 QC	51	/*
	52	* Accessing the pageblock without the zone lock. It could change to
	53	* "isolate" again in the meantime, but since we are just dumping the
	54	* state for debugging, it should be fine to accept a bit of
	55	* inaccuracy here due to racing.
	56	*/
	57	bool page_cma = is_migrate_cma_page(page);
fc36def9	58	int mapcount;
5b57b8f2	59	char *type = "";
fc36def9 PT	60
	61	/*
	62	* If struct page is poisoned don't access Page*() functions as that
	63	* leads to recursive loop. Page*() check for poisoned pages, and calls
	64	* dump_page() when detected.
	65	*/
	66	if (page_poisoned) {
e0392cf7	67	pr_warn("page:%px is uninitialized and poisoned", page);
fc36def9 PT	68	goto hex_only;
	69	}
	70
6197ab98	71	if (page < head \|\| (page >= head + MAX_ORDER_NR_PAGES)) {
e1ab96f8 MWO	72	/*
	73	* Corrupt page, so we cannot call page_mapping. Instead, do a
	74	* safe subset of the steps that page_mapping() does. Caution:
	75	* this will be misleading for tail pages, PageSwapCache pages,
	76	* and potentially other situations. (See the page_mapping()
	77	* implementation for what's missing here.)
	78	*/
	79	unsigned long tmp = (unsigned long)page->mapping;
	80
	81	if (tmp & PAGE_MAPPING_ANON)
	82	mapping = NULL;
	83	else
	84	mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
6197ab98 MWO	85	head = page;
	86	compound = false;
	87	} else {
	88	mapping = page_mapping(page);
	89	}
311ade0e	90
9996f05e KS	91	/*
	92	* Avoid VM_BUG_ON() in page_mapcount().
	93	* page->_mapcount space in struct page is used by sl[aou]b pages to
	94	* encode own info.
	95	*/
6197ab98 MWO	96	mapcount = PageSlab(head) ? 0 : page_mapcount(page);
6197ab98 MWO	97
54a75157	98	pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
452b557c	99	page, page_ref_count(head), mapcount, mapping,
54a75157	100	page_to_pgoff(page), page_to_pfn(page));
452b557c	101	if (compound) {
dc8fb2f2	102	if (hpage_pincount_available(page)) {
54a75157	103	pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
452b557c	104	head, compound_order(head),
6dc5ea16 JH	105	head_mapcount(head),
6dc5ea16 JH	106	head_pincount(head));
dc8fb2f2	107	} else {
54a75157	108	pr_warn("head:%p order:%u compound_mapcount:%d\n",
452b557c	109	head, compound_order(head),
6dc5ea16	110	head_mapcount(head));
dc8fb2f2	111	}
452b557c	112	}
6855ac4a	113	if (PageKsm(page))
5b57b8f2	114	type = "ksm ";
6855ac4a	115	else if (PageAnon(page))
5b57b8f2	116	type = "anon ";
1c6fb1d8	117	else if (mapping) {
9ad38265	118	struct inode *host;
002ae705	119	const struct address_space_operations *a_ops;
9ad38265 MWO	120	struct hlist_node *dentry_first;
9ad38265 MWO	121	struct dentry *dentry_ptr;
002ae705 VB	122	struct dentry dentry;
	123
	124	/*
	125	* mapping can be invalid pointer and we don't want to crash
	126	* accessing it, so probe everything depending on it carefully
	127	*/
9ad38265 MWO	128	if (get_kernel_nofault(host, &mapping->host) \|\|
	129	get_kernel_nofault(a_ops, &mapping->a_ops)) {
	130	pr_warn("failed to read mapping contents, not a valid kernel address?\n");
002ae705 VB	131	goto out_mapping;
	132	}
	133
	134	if (!host) {
9ad38265	135	pr_warn("aops:%ps\n", a_ops);
002ae705 VB	136	goto out_mapping;
	137	}
	138
9ad38265 MWO	139	if (get_kernel_nofault(dentry_first, &host->i_dentry.first)) {
	140	pr_warn("aops:%ps with invalid host inode %px\n",
	141	a_ops, host);
002ae705 VB	142	goto out_mapping;
	143	}
	144
	145	if (!dentry_first) {
9bdaf2cc	146	pr_warn("aops:%ps ino:%lx\n", a_ops, host->i_ino);
002ae705 VB	147	goto out_mapping;
	148	}
	149
	150	dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
9ad38265 MWO	151	if (get_kernel_nofault(dentry, dentry_ptr)) {
	152	pr_warn("aops:%ps with invalid dentry %px\n", a_ops,
	153	dentry_ptr);
002ae705 VB	154	} else {
	155	/*
	156	* if dentry is corrupted, the %pd handler may still
	157	* crash, but it's unlikely that we reach here with a
	158	* corrupted struct page
	159	*/
9bdaf2cc MWO	160	pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n",
9bdaf2cc MWO	161	a_ops, host->i_ino, &dentry);
002ae705	162	}
1c6fb1d8	163	}
002ae705	164	out_mapping:
edf14cdb	165	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
ff8e8116	166
0b93d59e	167	pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
4a55c047	168	page_cma ? " CMA" : "");
5b57b8f2	169
fc36def9	170	hex_only:
e0392cf7	171	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
46e8a3a0 VB	172	sizeof(unsigned long), page,
46e8a3a0 VB	173	sizeof(struct page), false);
6197ab98 MWO	174	if (head != page)
	175	print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
	176	sizeof(unsigned long), head,
	177	sizeof(struct page), false);
46e8a3a0	178
82742a3a	179	if (reason)
e0392cf7	180	pr_warn("page dumped because: %s\n", reason);
b8eceeb9	181
9edad6ea	182	#ifdef CONFIG_MEMCG
fc36def9	183	if (!page_poisoned && page->mem_cgroup)
e0392cf7	184	pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup);
9edad6ea	185	#endif
82742a3a SL	186	}
	187
	188	void dump_page(struct page page, const char reason)
	189	{
ff8e8116	190	__dump_page(page, reason);
4e462112	191	dump_page_owner(page);
82742a3a SL	192	}
	193	EXPORT_SYMBOL(dump_page);
	194
	195	#ifdef CONFIG_DEBUG_VM
	196
82742a3a SL	197	void dump_vma(const struct vm_area_struct *vma)
82742a3a SL	198	{
152a2d19 MW	199	pr_emerg("vma %px start %px end %px\n"
	200	"next %px prev %px mm %px\n"
	201	"prot %lx anon_vma %px vm_ops %px\n"
	202	"pgoff %lx file %px private_data %px\n"
b8eceeb9	203	"flags: %#lx(%pGv)\n",
82742a3a SL	204	vma, (void )vma->vm_start, (void )vma->vm_end, vma->vm_next,
	205	vma->vm_prev, vma->vm_mm,
	206	(unsigned long)pgprot_val(vma->vm_page_prot),
	207	vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
b8eceeb9 VB	208	vma->vm_file, vma->vm_private_data,
b8eceeb9 VB	209	vma->vm_flags, &vma->vm_flags);
82742a3a SL	210	}
	211	EXPORT_SYMBOL(dump_vma);
	212
31c9afa6 SL	213	void dump_mm(const struct mm_struct *mm)
31c9afa6 SL	214	{
7a9cdebd	215	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
31c9afa6	216	#ifdef CONFIG_MMU
152a2d19	217	"get_unmapped_area %px\n"
31c9afa6 SL	218	#endif
31c9afa6 SL	219	"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
152a2d19	220	"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
31c9afa6	221	"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
70f8a3ca	222	"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
31c9afa6 SL	223	"start_code %lx end_code %lx start_data %lx end_data %lx\n"
	224	"start_brk %lx brk %lx start_stack %lx\n"
	225	"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
152a2d19	226	"binfmt %px flags %lx core_state %px\n"
31c9afa6	227	#ifdef CONFIG_AIO
152a2d19	228	"ioctx_table %px\n"
31c9afa6 SL	229	#endif
31c9afa6 SL	230	#ifdef CONFIG_MEMCG
152a2d19	231	"owner %px "
31c9afa6	232	#endif
152a2d19	233	"exe_file %px\n"
31c9afa6	234	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	235	"notifier_subscriptions %px\n"
31c9afa6 SL	236	#endif
	237	#ifdef CONFIG_NUMA_BALANCING
	238	"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
	239	#endif
31c9afa6	240	"tlb_flush_pending %d\n"
b8eceeb9	241	"def_flags: %#lx(%pGv)\n",
31c9afa6	242
7a9cdebd	243	mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
31c9afa6 SL	244	#ifdef CONFIG_MMU
	245	mm->get_unmapped_area,
	246	#endif
	247	mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
	248	mm->pgd, atomic_read(&mm->mm_users),
	249	atomic_read(&mm->mm_count),
af5b0f6a	250	mm_pgtables_bytes(mm),
31c9afa6 SL	251	mm->map_count,
31c9afa6 SL	252	mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
44dc1b1f	253	(u64)atomic64_read(&mm->pinned_vm),
70f8a3ca	254	mm->data_vm, mm->exec_vm, mm->stack_vm,
31c9afa6 SL	255	mm->start_code, mm->end_code, mm->start_data, mm->end_data,
	256	mm->start_brk, mm->brk, mm->start_stack,
	257	mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
	258	mm->binfmt, mm->flags, mm->core_state,
	259	#ifdef CONFIG_AIO
	260	mm->ioctx_table,
	261	#endif
	262	#ifdef CONFIG_MEMCG
	263	mm->owner,
	264	#endif
	265	mm->exe_file,
	266	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	267	mm->notifier_subscriptions,
31c9afa6 SL	268	#endif
	269	#ifdef CONFIG_NUMA_BALANCING
	270	mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
	271	#endif
16af97dc	272	atomic_read(&mm->tlb_flush_pending),
b8eceeb9 VB	273	mm->def_flags, &mm->def_flags
b8eceeb9 VB	274	);
31c9afa6 SL	275	}
31c9afa6 SL	276
f682a97a AD	277	static bool page_init_poisoning __read_mostly = true;
	278
	279	static int __init setup_vm_debug(char *str)
	280	{
	281	bool __page_init_poisoning = true;
	282
	283	/*
	284	* Calling vm_debug with no arguments is equivalent to requesting
	285	* to enable all debugging options we can control.
	286	*/
	287	if (str++ != '=' \|\| !str)
	288	goto out;
	289
	290	__page_init_poisoning = false;
	291	if (*str == '-')
	292	goto out;
	293
	294	while (*str) {
	295	switch (tolower(*str)) {
	296	case'p':
	297	__page_init_poisoning = true;
	298	break;
	299	default:
	300	pr_err("vm_debug option '%c' unknown. skipped\n",
	301	*str);
	302	}
	303
	304	str++;
	305	}
	306	out:
	307	if (page_init_poisoning && !__page_init_poisoning)
	308	pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
	309
	310	page_init_poisoning = __page_init_poisoning;
	311
	312	return 1;
	313	}
	314	__setup("vm_debug", setup_vm_debug);
	315
	316	void page_init_poison(struct page *page, size_t size)
	317	{
	318	if (page_init_poisoning)
	319	memset(page, PAGE_POISON_PATTERN, size);
	320	}
	321	EXPORT_SYMBOL_GPL(page_init_poison);
82742a3a	322	#endif /* CONFIG_DEBUG_VM */