[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}
};

static void __dump_page(struct page *page)
{
	struct page *head = compound_head(page);
	struct address_space *mapping;
	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 (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_compound_mapcount(head),
					head_compound_pincount(head));
		} else {
			pr_warn("head:%p order:%u compound_mapcount:%d\n",
					head, compound_order(head),
					head_compound_mapcount(head));
		}
	}

#ifdef CONFIG_MEMCG
	if (head->memcg_data)
		pr_warn("memcg:%lx\n", head->memcg_data);
#endif
	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;
		unsigned long ino;

		/*
		 * 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) ||
		    get_kernel_nofault(ino, &host->i_ino)) {
			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, 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 ino:%lx with invalid dentry %px\n",
					a_ops, ino, 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, 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" : "");
	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);
}

void dump_page(struct page *page, const char *reason)
{
	if (PagePoisoned(page))
		pr_warn("page:%p is uninitialized and poisoned", 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\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
be7c701f	45	static void __dump_page(struct page *page)
82742a3a	46	{
6197ab98	47	struct page *head = compound_head(page);
311ade0e	48	struct address_space *mapping;
6197ab98	49	bool compound = PageCompound(page);
4a55c047 QC	50	/*
	51	* Accessing the pageblock without the zone lock. It could change to
	52	* "isolate" again in the meantime, but since we are just dumping the
	53	* state for debugging, it should be fine to accept a bit of
	54	* inaccuracy here due to racing.
	55	*/
	56	bool page_cma = is_migrate_cma_page(page);
fc36def9	57	int mapcount;
5b57b8f2	58	char *type = "";
fc36def9	59
6197ab98	60	if (page < head \|\| (page >= head + MAX_ORDER_NR_PAGES)) {
e1ab96f8 MWO	61	/*
	62	* Corrupt page, so we cannot call page_mapping. Instead, do a
	63	* safe subset of the steps that page_mapping() does. Caution:
	64	* this will be misleading for tail pages, PageSwapCache pages,
	65	* and potentially other situations. (See the page_mapping()
	66	* implementation for what's missing here.)
	67	*/
	68	unsigned long tmp = (unsigned long)page->mapping;
	69
	70	if (tmp & PAGE_MAPPING_ANON)
	71	mapping = NULL;
	72	else
	73	mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
6197ab98 MWO	74	head = page;
	75	compound = false;
	76	} else {
	77	mapping = page_mapping(page);
	78	}
311ade0e	79
9996f05e KS	80	/*
	81	* Avoid VM_BUG_ON() in page_mapcount().
	82	* page->_mapcount space in struct page is used by sl[aou]b pages to
	83	* encode own info.
	84	*/
6197ab98 MWO	85	mapcount = PageSlab(head) ? 0 : page_mapcount(page);
6197ab98 MWO	86
54a75157	87	pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
452b557c	88	page, page_ref_count(head), mapcount, mapping,
54a75157	89	page_to_pgoff(page), page_to_pfn(page));
452b557c	90	if (compound) {
dc8fb2f2	91	if (hpage_pincount_available(page)) {
54a75157	92	pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
452b557c	93	head, compound_order(head),
bac3cf4d JH	94	head_compound_mapcount(head),
bac3cf4d JH	95	head_compound_pincount(head));
dc8fb2f2	96	} else {
54a75157	97	pr_warn("head:%p order:%u compound_mapcount:%d\n",
452b557c	98	head, compound_order(head),
bac3cf4d	99	head_compound_mapcount(head));
dc8fb2f2	100	}
452b557c	101	}
91f5345a MWO	102
	103	#ifdef CONFIG_MEMCG
	104	if (head->memcg_data)
	105	pr_warn("memcg:%lx\n", head->memcg_data);
	106	#endif
6855ac4a	107	if (PageKsm(page))
5b57b8f2	108	type = "ksm ";
6855ac4a	109	else if (PageAnon(page))
5b57b8f2	110	type = "anon ";
1c6fb1d8	111	else if (mapping) {
9ad38265	112	struct inode *host;
002ae705	113	const struct address_space_operations *a_ops;
9ad38265 MWO	114	struct hlist_node *dentry_first;
9ad38265 MWO	115	struct dentry *dentry_ptr;
002ae705	116	struct dentry dentry;
853322a6	117	unsigned long ino;
002ae705 VB	118
	119	/*
	120	* mapping can be invalid pointer and we don't want to crash
	121	* accessing it, so probe everything depending on it carefully
	122	*/
9ad38265 MWO	123	if (get_kernel_nofault(host, &mapping->host) \|\|
	124	get_kernel_nofault(a_ops, &mapping->a_ops)) {
	125	pr_warn("failed to read mapping contents, not a valid kernel address?\n");
002ae705 VB	126	goto out_mapping;
	127	}
	128
	129	if (!host) {
9ad38265	130	pr_warn("aops:%ps\n", a_ops);
002ae705 VB	131	goto out_mapping;
	132	}
	133
853322a6 MWO	134	if (get_kernel_nofault(dentry_first, &host->i_dentry.first) \|\|
853322a6 MWO	135	get_kernel_nofault(ino, &host->i_ino)) {
9ad38265 MWO	136	pr_warn("aops:%ps with invalid host inode %px\n",
9ad38265 MWO	137	a_ops, host);
002ae705 VB	138	goto out_mapping;
	139	}
	140
	141	if (!dentry_first) {
853322a6	142	pr_warn("aops:%ps ino:%lx\n", a_ops, ino);
002ae705 VB	143	goto out_mapping;
	144	}
	145
	146	dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
9ad38265	147	if (get_kernel_nofault(dentry, dentry_ptr)) {
853322a6 MWO	148	pr_warn("aops:%ps ino:%lx with invalid dentry %px\n",
853322a6 MWO	149	a_ops, ino, dentry_ptr);
002ae705 VB	150	} else {
	151	/*
	152	* if dentry is corrupted, the %pd handler may still
	153	* crash, but it's unlikely that we reach here with a
	154	* corrupted struct page
	155	*/
9bdaf2cc	156	pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n",
853322a6	157	a_ops, ino, &dentry);
002ae705	158	}
1c6fb1d8	159	}
002ae705	160	out_mapping:
edf14cdb	161	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
ff8e8116	162
0b93d59e	163	pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
4a55c047	164	page_cma ? " CMA" : "");
e0392cf7	165	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
46e8a3a0 VB	166	sizeof(unsigned long), page,
46e8a3a0 VB	167	sizeof(struct page), false);
6197ab98 MWO	168	if (head != page)
	169	print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
	170	sizeof(unsigned long), head,
	171	sizeof(struct page), false);
82742a3a SL	172	}
	173
	174	void dump_page(struct page page, const char reason)
	175	{
be7c701f MWO	176	if (PagePoisoned(page))
	177	pr_warn("page:%p is uninitialized and poisoned", page);
	178	else
	179	__dump_page(page);
	180	if (reason)
	181	pr_warn("page dumped because: %s\n", reason);
4e462112	182	dump_page_owner(page);
82742a3a SL	183	}
	184	EXPORT_SYMBOL(dump_page);
	185
	186	#ifdef CONFIG_DEBUG_VM
	187
82742a3a SL	188	void dump_vma(const struct vm_area_struct *vma)
82742a3a SL	189	{
152a2d19 MW	190	pr_emerg("vma %px start %px end %px\n"
	191	"next %px prev %px mm %px\n"
	192	"prot %lx anon_vma %px vm_ops %px\n"
	193	"pgoff %lx file %px private_data %px\n"
b8eceeb9	194	"flags: %#lx(%pGv)\n",
82742a3a SL	195	vma, (void )vma->vm_start, (void )vma->vm_end, vma->vm_next,
	196	vma->vm_prev, vma->vm_mm,
	197	(unsigned long)pgprot_val(vma->vm_page_prot),
	198	vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
b8eceeb9 VB	199	vma->vm_file, vma->vm_private_data,
b8eceeb9 VB	200	vma->vm_flags, &vma->vm_flags);
82742a3a SL	201	}
	202	EXPORT_SYMBOL(dump_vma);
	203
31c9afa6 SL	204	void dump_mm(const struct mm_struct *mm)
31c9afa6 SL	205	{
7a9cdebd	206	pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
31c9afa6	207	#ifdef CONFIG_MMU
152a2d19	208	"get_unmapped_area %px\n"
31c9afa6 SL	209	#endif
31c9afa6 SL	210	"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
152a2d19	211	"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
31c9afa6	212	"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
70f8a3ca	213	"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
31c9afa6 SL	214	"start_code %lx end_code %lx start_data %lx end_data %lx\n"
	215	"start_brk %lx brk %lx start_stack %lx\n"
	216	"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
152a2d19	217	"binfmt %px flags %lx core_state %px\n"
31c9afa6	218	#ifdef CONFIG_AIO
152a2d19	219	"ioctx_table %px\n"
31c9afa6 SL	220	#endif
31c9afa6 SL	221	#ifdef CONFIG_MEMCG
152a2d19	222	"owner %px "
31c9afa6	223	#endif
152a2d19	224	"exe_file %px\n"
31c9afa6	225	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	226	"notifier_subscriptions %px\n"
31c9afa6 SL	227	#endif
	228	#ifdef CONFIG_NUMA_BALANCING
	229	"numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
	230	#endif
31c9afa6	231	"tlb_flush_pending %d\n"
b8eceeb9	232	"def_flags: %#lx(%pGv)\n",
31c9afa6	233
7a9cdebd	234	mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
31c9afa6 SL	235	#ifdef CONFIG_MMU
	236	mm->get_unmapped_area,
	237	#endif
	238	mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
	239	mm->pgd, atomic_read(&mm->mm_users),
	240	atomic_read(&mm->mm_count),
af5b0f6a	241	mm_pgtables_bytes(mm),
31c9afa6 SL	242	mm->map_count,
31c9afa6 SL	243	mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
44dc1b1f	244	(u64)atomic64_read(&mm->pinned_vm),
70f8a3ca	245	mm->data_vm, mm->exec_vm, mm->stack_vm,
31c9afa6 SL	246	mm->start_code, mm->end_code, mm->start_data, mm->end_data,
	247	mm->start_brk, mm->brk, mm->start_stack,
	248	mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
	249	mm->binfmt, mm->flags, mm->core_state,
	250	#ifdef CONFIG_AIO
	251	mm->ioctx_table,
	252	#endif
	253	#ifdef CONFIG_MEMCG
	254	mm->owner,
	255	#endif
	256	mm->exe_file,
	257	#ifdef CONFIG_MMU_NOTIFIER
984cfe4e	258	mm->notifier_subscriptions,
31c9afa6 SL	259	#endif
	260	#ifdef CONFIG_NUMA_BALANCING
	261	mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq,
	262	#endif
16af97dc	263	atomic_read(&mm->tlb_flush_pending),
b8eceeb9 VB	264	mm->def_flags, &mm->def_flags
b8eceeb9 VB	265	);
31c9afa6 SL	266	}
31c9afa6 SL	267
f682a97a AD	268	static bool page_init_poisoning __read_mostly = true;
	269
	270	static int __init setup_vm_debug(char *str)
	271	{
	272	bool __page_init_poisoning = true;
	273
	274	/*
	275	* Calling vm_debug with no arguments is equivalent to requesting
	276	* to enable all debugging options we can control.
	277	*/
	278	if (str++ != '=' \|\| !str)
	279	goto out;
	280
	281	__page_init_poisoning = false;
	282	if (*str == '-')
	283	goto out;
	284
	285	while (*str) {
	286	switch (tolower(*str)) {
	287	case'p':
	288	__page_init_poisoning = true;
	289	break;
	290	default:
	291	pr_err("vm_debug option '%c' unknown. skipped\n",
	292	*str);
	293	}
	294
	295	str++;
	296	}
	297	out:
	298	if (page_init_poisoning && !__page_init_poisoning)
	299	pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
	300
	301	page_init_poisoning = __page_init_poisoning;
	302
	303	return 1;
	304	}
	305	__setup("vm_debug", setup_vm_debug);
	306
	307	void page_init_poison(struct page *page, size_t size)
	308	{
	309	if (page_init_poisoning)
	310	memset(page, PAGE_POISON_PATTERN, size);
	311	}
	312	EXPORT_SYMBOL_GPL(page_init_poison);
82742a3a	313	#endif /* CONFIG_DEBUG_VM */