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![Jaewon Kim](/assets/img/avatar_default.png)
online_page_ext() and page_ext_init() allocate page_ext for each section, but they do not allocate if the first PFN is !pfn_present(pfn) or !pfn_valid(pfn). Then section->page_ext remains as NULL. lookup_page_ext checks NULL only if CONFIG_DEBUG_VM is enabled. For a valid PFN, __set_page_owner will try to get page_ext through lookup_page_ext. Without CONFIG_DEBUG_VM lookup_page_ext will misuse NULL pointer as value 0. This incurrs invalid address access. This is the panic example when PFN 0x100000 is not valid but PFN 0x13FC00 is being used for page_ext. section->page_ext is NULL, get_entry returned invalid page_ext address as 0x1DFA000 for a PFN 0x13FC00. To avoid this panic, CONFIG_DEBUG_VM should be removed so that page_ext will be checked at all times. Unable to handle kernel paging request at virtual address 01dfa014 ------------[ cut here ]------------ Kernel BUG at ffffff80082371e0 [verbose debug info unavailable] Internal error: Oops: 96000045 [#1] PREEMPT SMP Modules linked in: PC is at __set_page_owner+0x48/0x78 LR is at __set_page_owner+0x44/0x78 __set_page_owner+0x48/0x78 get_page_from_freelist+0x880/0x8e8 __alloc_pages_nodemask+0x14c/0xc48 __do_page_cache_readahead+0xdc/0x264 filemap_fault+0x2ac/0x550 ext4_filemap_fault+0x3c/0x58 __do_fault+0x80/0x120 handle_mm_fault+0x704/0xbb0 do_page_fault+0x2e8/0x394 do_mem_abort+0x88/0x124 Pre-4.7 kernels also need commitf86e427197
("mm: check the return value of lookup_page_ext for all call sites"). Link: http://lkml.kernel.org/r/20171107094131.14621-1-jaewon31.kim@samsung.com Fixes:eefa864b70
("mm/page_ext: resurrect struct page extending code for debugging") Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Joonsoo Kim <js1304@gmail.com> Cc: <stable@vger.kernel.org> [depends onf86e427197
, see above] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
422 lines
11 KiB
C
422 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/bootmem.h>
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#include <linux/page_ext.h>
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#include <linux/memory.h>
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#include <linux/vmalloc.h>
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#include <linux/kmemleak.h>
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#include <linux/page_owner.h>
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#include <linux/page_idle.h>
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/*
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* struct page extension
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*
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* This is the feature to manage memory for extended data per page.
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*
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* Until now, we must modify struct page itself to store extra data per page.
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* This requires rebuilding the kernel and it is really time consuming process.
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* And, sometimes, rebuild is impossible due to third party module dependency.
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* At last, enlarging struct page could cause un-wanted system behaviour change.
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*
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* This feature is intended to overcome above mentioned problems. This feature
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* allocates memory for extended data per page in certain place rather than
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* the struct page itself. This memory can be accessed by the accessor
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* functions provided by this code. During the boot process, it checks whether
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* allocation of huge chunk of memory is needed or not. If not, it avoids
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* allocating memory at all. With this advantage, we can include this feature
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* into the kernel in default and can avoid rebuild and solve related problems.
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*
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* To help these things to work well, there are two callbacks for clients. One
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* is the need callback which is mandatory if user wants to avoid useless
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* memory allocation at boot-time. The other is optional, init callback, which
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* is used to do proper initialization after memory is allocated.
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*
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* The need callback is used to decide whether extended memory allocation is
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* needed or not. Sometimes users want to deactivate some features in this
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* boot and extra memory would be unneccessary. In this case, to avoid
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* allocating huge chunk of memory, each clients represent their need of
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* extra memory through the need callback. If one of the need callbacks
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* returns true, it means that someone needs extra memory so that
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* page extension core should allocates memory for page extension. If
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* none of need callbacks return true, memory isn't needed at all in this boot
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* and page extension core can skip to allocate memory. As result,
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* none of memory is wasted.
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*
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* When need callback returns true, page_ext checks if there is a request for
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* extra memory through size in struct page_ext_operations. If it is non-zero,
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* extra space is allocated for each page_ext entry and offset is returned to
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* user through offset in struct page_ext_operations.
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*
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* The init callback is used to do proper initialization after page extension
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* is completely initialized. In sparse memory system, extra memory is
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* allocated some time later than memmap is allocated. In other words, lifetime
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* of memory for page extension isn't same with memmap for struct page.
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* Therefore, clients can't store extra data until page extension is
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* initialized, even if pages are allocated and used freely. This could
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* cause inadequate state of extra data per page, so, to prevent it, client
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* can utilize this callback to initialize the state of it correctly.
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*/
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static struct page_ext_operations *page_ext_ops[] = {
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&debug_guardpage_ops,
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#ifdef CONFIG_PAGE_OWNER
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&page_owner_ops,
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#endif
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#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
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&page_idle_ops,
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#endif
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};
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static unsigned long total_usage;
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static unsigned long extra_mem;
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static bool __init invoke_need_callbacks(void)
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{
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int i;
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int entries = ARRAY_SIZE(page_ext_ops);
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bool need = false;
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for (i = 0; i < entries; i++) {
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if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
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page_ext_ops[i]->offset = sizeof(struct page_ext) +
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extra_mem;
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extra_mem += page_ext_ops[i]->size;
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need = true;
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}
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}
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return need;
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}
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static void __init invoke_init_callbacks(void)
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{
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int i;
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int entries = ARRAY_SIZE(page_ext_ops);
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for (i = 0; i < entries; i++) {
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if (page_ext_ops[i]->init)
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page_ext_ops[i]->init();
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}
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}
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static unsigned long get_entry_size(void)
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{
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return sizeof(struct page_ext) + extra_mem;
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}
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static inline struct page_ext *get_entry(void *base, unsigned long index)
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{
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return base + get_entry_size() * index;
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}
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#if !defined(CONFIG_SPARSEMEM)
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void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
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{
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pgdat->node_page_ext = NULL;
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}
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struct page_ext *lookup_page_ext(struct page *page)
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{
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unsigned long pfn = page_to_pfn(page);
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unsigned long index;
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struct page_ext *base;
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base = NODE_DATA(page_to_nid(page))->node_page_ext;
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/*
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* The sanity checks the page allocator does upon freeing a
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* page can reach here before the page_ext arrays are
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* allocated when feeding a range of pages to the allocator
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* for the first time during bootup or memory hotplug.
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*/
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if (unlikely(!base))
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return NULL;
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index = pfn - round_down(node_start_pfn(page_to_nid(page)),
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MAX_ORDER_NR_PAGES);
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return get_entry(base, index);
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}
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static int __init alloc_node_page_ext(int nid)
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{
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struct page_ext *base;
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unsigned long table_size;
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unsigned long nr_pages;
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nr_pages = NODE_DATA(nid)->node_spanned_pages;
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if (!nr_pages)
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return 0;
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/*
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* Need extra space if node range is not aligned with
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* MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
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* checks buddy's status, range could be out of exact node range.
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*/
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if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
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!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
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nr_pages += MAX_ORDER_NR_PAGES;
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table_size = get_entry_size() * nr_pages;
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base = memblock_virt_alloc_try_nid_nopanic(
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table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
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BOOTMEM_ALLOC_ACCESSIBLE, nid);
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if (!base)
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return -ENOMEM;
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NODE_DATA(nid)->node_page_ext = base;
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total_usage += table_size;
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return 0;
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}
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void __init page_ext_init_flatmem(void)
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{
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int nid, fail;
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if (!invoke_need_callbacks())
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return;
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for_each_online_node(nid) {
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fail = alloc_node_page_ext(nid);
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if (fail)
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goto fail;
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}
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pr_info("allocated %ld bytes of page_ext\n", total_usage);
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invoke_init_callbacks();
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return;
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fail:
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pr_crit("allocation of page_ext failed.\n");
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panic("Out of memory");
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}
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#else /* CONFIG_FLAT_NODE_MEM_MAP */
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struct page_ext *lookup_page_ext(struct page *page)
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{
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unsigned long pfn = page_to_pfn(page);
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struct mem_section *section = __pfn_to_section(pfn);
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/*
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* The sanity checks the page allocator does upon freeing a
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* page can reach here before the page_ext arrays are
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* allocated when feeding a range of pages to the allocator
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* for the first time during bootup or memory hotplug.
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*/
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if (!section->page_ext)
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return NULL;
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return get_entry(section->page_ext, pfn);
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}
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static void *__meminit alloc_page_ext(size_t size, int nid)
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{
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gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
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void *addr = NULL;
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addr = alloc_pages_exact_nid(nid, size, flags);
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if (addr) {
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kmemleak_alloc(addr, size, 1, flags);
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return addr;
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}
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addr = vzalloc_node(size, nid);
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return addr;
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}
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static int __meminit init_section_page_ext(unsigned long pfn, int nid)
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{
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struct mem_section *section;
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struct page_ext *base;
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unsigned long table_size;
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section = __pfn_to_section(pfn);
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if (section->page_ext)
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return 0;
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table_size = get_entry_size() * PAGES_PER_SECTION;
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base = alloc_page_ext(table_size, nid);
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/*
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* The value stored in section->page_ext is (base - pfn)
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* and it does not point to the memory block allocated above,
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* causing kmemleak false positives.
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*/
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kmemleak_not_leak(base);
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if (!base) {
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pr_err("page ext allocation failure\n");
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return -ENOMEM;
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}
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/*
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* The passed "pfn" may not be aligned to SECTION. For the calculation
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* we need to apply a mask.
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*/
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pfn &= PAGE_SECTION_MASK;
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section->page_ext = (void *)base - get_entry_size() * pfn;
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total_usage += table_size;
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return 0;
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}
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#ifdef CONFIG_MEMORY_HOTPLUG
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static void free_page_ext(void *addr)
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{
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if (is_vmalloc_addr(addr)) {
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vfree(addr);
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} else {
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struct page *page = virt_to_page(addr);
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size_t table_size;
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table_size = get_entry_size() * PAGES_PER_SECTION;
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BUG_ON(PageReserved(page));
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free_pages_exact(addr, table_size);
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}
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}
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static void __free_page_ext(unsigned long pfn)
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{
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struct mem_section *ms;
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struct page_ext *base;
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ms = __pfn_to_section(pfn);
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if (!ms || !ms->page_ext)
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return;
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base = get_entry(ms->page_ext, pfn);
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free_page_ext(base);
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ms->page_ext = NULL;
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}
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static int __meminit online_page_ext(unsigned long start_pfn,
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unsigned long nr_pages,
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int nid)
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{
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unsigned long start, end, pfn;
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int fail = 0;
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start = SECTION_ALIGN_DOWN(start_pfn);
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end = SECTION_ALIGN_UP(start_pfn + nr_pages);
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if (nid == -1) {
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/*
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* In this case, "nid" already exists and contains valid memory.
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* "start_pfn" passed to us is a pfn which is an arg for
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* online__pages(), and start_pfn should exist.
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*/
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nid = pfn_to_nid(start_pfn);
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VM_BUG_ON(!node_state(nid, N_ONLINE));
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}
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for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
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if (!pfn_present(pfn))
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continue;
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fail = init_section_page_ext(pfn, nid);
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}
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if (!fail)
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return 0;
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/* rollback */
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for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
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__free_page_ext(pfn);
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return -ENOMEM;
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}
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static int __meminit offline_page_ext(unsigned long start_pfn,
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unsigned long nr_pages, int nid)
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{
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unsigned long start, end, pfn;
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start = SECTION_ALIGN_DOWN(start_pfn);
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end = SECTION_ALIGN_UP(start_pfn + nr_pages);
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for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
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__free_page_ext(pfn);
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return 0;
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}
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static int __meminit page_ext_callback(struct notifier_block *self,
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unsigned long action, void *arg)
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{
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struct memory_notify *mn = arg;
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int ret = 0;
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switch (action) {
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case MEM_GOING_ONLINE:
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ret = online_page_ext(mn->start_pfn,
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mn->nr_pages, mn->status_change_nid);
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break;
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case MEM_OFFLINE:
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offline_page_ext(mn->start_pfn,
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mn->nr_pages, mn->status_change_nid);
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break;
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case MEM_CANCEL_ONLINE:
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offline_page_ext(mn->start_pfn,
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mn->nr_pages, mn->status_change_nid);
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break;
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case MEM_GOING_OFFLINE:
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break;
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case MEM_ONLINE:
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case MEM_CANCEL_OFFLINE:
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break;
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}
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return notifier_from_errno(ret);
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}
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#endif
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void __init page_ext_init(void)
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{
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unsigned long pfn;
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int nid;
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if (!invoke_need_callbacks())
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return;
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for_each_node_state(nid, N_MEMORY) {
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unsigned long start_pfn, end_pfn;
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start_pfn = node_start_pfn(nid);
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end_pfn = node_end_pfn(nid);
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/*
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* start_pfn and end_pfn may not be aligned to SECTION and the
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* page->flags of out of node pages are not initialized. So we
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* scan [start_pfn, the biggest section's pfn < end_pfn) here.
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*/
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for (pfn = start_pfn; pfn < end_pfn;
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pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
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if (!pfn_valid(pfn))
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continue;
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/*
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* Nodes's pfns can be overlapping.
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* We know some arch can have a nodes layout such as
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* -------------pfn-------------->
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* N0 | N1 | N2 | N0 | N1 | N2|....
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*
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* Take into account DEFERRED_STRUCT_PAGE_INIT.
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*/
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if (early_pfn_to_nid(pfn) != nid)
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continue;
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if (init_section_page_ext(pfn, nid))
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goto oom;
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cond_resched();
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}
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}
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hotplug_memory_notifier(page_ext_callback, 0);
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pr_info("allocated %ld bytes of page_ext\n", total_usage);
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invoke_init_callbacks();
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return;
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oom:
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panic("Out of memory");
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}
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void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
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{
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}
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#endif
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