6e12c5b7d4
For CMA allocation, it's really critical to migrate a page but sometimes it fails. One of the reasons is some driver holds a page refcount for a long time so VM couldn't migrate the page at that time. The concern here is there is no way to find the who hold the refcount of the page effectively. This patch introduces feature to keep tracking page's pinner. All get_page sites are vulnerable to pin a page for a long time but the cost to keep track it would be significat since get_page is the most frequent kernel operation. Furthermore, the page could be not user page but kernel page which is not related to the page migration failure. So, this patch keeps tracking only get_user_pages/follow_page with (FOLL_GET|PIN friends because they are the very common APIs to pin user pages which could cause migration failure and the less frequent than get_page so runtime cost wouldn't be that big but could cover many cases effectively. This patch also introduces put_user_page API. It aims for attributing "the pinner releases the page from now on" while it release the page refcount. Thus, any user of get_user_pages/follow_page(FOLL_GET) must use put_user_page as pair of those functions. Otherwise, page_pinner will treat them long term pinner as false postive but nothing should affect stability. * $debugfs/page_pinner/threshold It indicates threshold(microsecond) to flag long term pinning. It's configurable(Default is 300000us). Once you write new value to the threshold, old data will clear. * $debugfs/page_pinner/longterm_pinner It shows call sites where the duration of pinning was greater than the threshold. Internally, it uses a static array to keep 4096 elements and overwrites old ones once overflow happens. Therefore, you could lose some information. example) Page pinned ts 76953865787 us count 1 PFN 9856945 Block 9625 type Movable Flags 0x8000000000080014(uptodate|lru|swapbacked) __set_page_pinner+0x34/0xcc try_grab_page+0x19c/0x1a0 follow_page_pte+0x1c0/0x33c follow_page_mask+0xc0/0xc8 __get_user_pages+0x178/0x414 __gup_longterm_locked+0x80/0x148 internal_get_user_pages_fast+0x140/0x174 pin_user_pages_fast+0x24/0x40 CCC BBB AAA __arm64_sys_ioctl+0x94/0xd0 el0_svc_common+0xa4/0x180 do_el0_svc+0x28/0x88 el0_svc+0x14/0x24 note: page_pinner doesn't guarantee attributing/unattributing are atomic if they happen at the same time. It's just best effort so false-positive could happen. Bug: 183414571 Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Minchan Kim <minchan@google.com> Change-Id: Ife37ec360eef993d390b9c131732218a4dfd2f04
327 lines
8.5 KiB
C
327 lines
8.5 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 <linux/page_pinner.h>
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#include <linux/ctype.h>
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#include "internal.h"
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const 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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struct page *head = compound_head(page);
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struct address_space *mapping;
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bool page_poisoned = PagePoisoned(page);
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bool compound = PageCompound(page);
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/*
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* Accessing the pageblock without the zone lock. It could change to
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* "isolate" again in the meantime, but since we are just dumping the
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* state for debugging, it should be fine to accept a bit of
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* inaccuracy here due to racing.
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*/
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bool page_cma = is_migrate_cma_page(page);
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int mapcount;
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char *type = "";
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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_warn("page:%px is uninitialized and poisoned", page);
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goto hex_only;
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}
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if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
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/*
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* Corrupt page, so we cannot call page_mapping. Instead, do a
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* safe subset of the steps that page_mapping() does. Caution:
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* this will be misleading for tail pages, PageSwapCache pages,
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* and potentially other situations. (See the page_mapping()
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* implementation for what's missing here.)
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*/
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unsigned long tmp = (unsigned long)page->mapping;
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if (tmp & PAGE_MAPPING_ANON)
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mapping = NULL;
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else
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mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
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head = page;
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compound = false;
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} else {
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mapping = page_mapping(page);
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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(head) ? 0 : page_mapcount(page);
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pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
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page, page_ref_count(head), mapcount, mapping,
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page_to_pgoff(page), page_to_pfn(page));
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if (compound) {
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if (hpage_pincount_available(page)) {
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pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
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head, compound_order(head),
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head_compound_mapcount(head),
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head_compound_pincount(head));
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} else {
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pr_warn("head:%p order:%u compound_mapcount:%d\n",
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head, compound_order(head),
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head_compound_mapcount(head));
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}
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}
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if (PageKsm(page))
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type = "ksm ";
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else if (PageAnon(page))
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type = "anon ";
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else if (mapping) {
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struct inode *host;
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const struct address_space_operations *a_ops;
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struct hlist_node *dentry_first;
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struct dentry *dentry_ptr;
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struct dentry dentry;
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unsigned long ino;
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/*
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* mapping can be invalid pointer and we don't want to crash
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* accessing it, so probe everything depending on it carefully
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*/
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if (get_kernel_nofault(host, &mapping->host) ||
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get_kernel_nofault(a_ops, &mapping->a_ops)) {
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pr_warn("failed to read mapping contents, not a valid kernel address?\n");
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goto out_mapping;
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}
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if (!host) {
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pr_warn("aops:%ps\n", a_ops);
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goto out_mapping;
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}
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if (get_kernel_nofault(dentry_first, &host->i_dentry.first) ||
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get_kernel_nofault(ino, &host->i_ino)) {
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pr_warn("aops:%ps with invalid host inode %px\n",
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a_ops, host);
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goto out_mapping;
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}
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if (!dentry_first) {
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pr_warn("aops:%ps ino:%lx\n", a_ops, ino);
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goto out_mapping;
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}
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dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
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if (get_kernel_nofault(dentry, dentry_ptr)) {
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pr_warn("aops:%ps ino:%lx with invalid dentry %px\n",
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a_ops, ino, dentry_ptr);
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} else {
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/*
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* if dentry is corrupted, the %pd handler may still
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* crash, but it's unlikely that we reach here with a
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* corrupted struct page
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*/
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pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n",
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a_ops, ino, &dentry);
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}
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}
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out_mapping:
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BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
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pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
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page_cma ? " CMA" : "");
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hex_only:
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print_hex_dump(KERN_WARNING, "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 (head != page)
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print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
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sizeof(unsigned long), head,
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sizeof(struct page), false);
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if (reason)
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pr_warn("page dumped because: %s\n", reason);
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#ifdef CONFIG_MEMCG
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if (!page_poisoned && page->mem_cgroup)
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pr_warn("page->mem_cgroup:%px\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(page, reason);
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dump_page_owner(page);
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dump_page_pinner(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 %llx 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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"notifier_subscriptions %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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(u64)atomic64_read(&mm->pinned_vm),
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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->notifier_subscriptions,
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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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static bool page_init_poisoning __read_mostly = true;
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static int __init setup_vm_debug(char *str)
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{
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bool __page_init_poisoning = true;
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/*
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* Calling vm_debug with no arguments is equivalent to requesting
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* to enable all debugging options we can control.
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*/
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if (*str++ != '=' || !*str)
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goto out;
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__page_init_poisoning = false;
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if (*str == '-')
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goto out;
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while (*str) {
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switch (tolower(*str)) {
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case'p':
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__page_init_poisoning = true;
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break;
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default:
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pr_err("vm_debug option '%c' unknown. skipped\n",
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*str);
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}
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str++;
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}
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out:
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if (page_init_poisoning && !__page_init_poisoning)
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pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
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page_init_poisoning = __page_init_poisoning;
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return 1;
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}
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__setup("vm_debug", setup_vm_debug);
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void page_init_poison(struct page *page, size_t size)
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{
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if (page_init_poisoning)
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memset(page, PAGE_POISON_PATTERN, size);
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}
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EXPORT_SYMBOL_GPL(page_init_poison);
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#endif /* CONFIG_DEBUG_VM */
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