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    SubjectRe: [PATCH] mm: fix a regression with HIGHMEM introduced by changeset 7f1290f2f2a4d
    On Wed, 14 Nov 2012 22:52:03 +0800
    Jiang Liu <liuj97@gmail.com> wrote:

    > So how about totally reverting the changeset 7f1290f2f2a4d2c3f1b7ce8e87256e052ca23125
    > and I will post another version once I found a cleaner way?

    We do need to get this regression fixed and I guess that a
    straightforward revert is an acceptable way of doing that, for now.


    I queued the below, with a plan to send it to Linus next week.


    From: Andrew Morton <akpm@linux-foundation.org>
    Subject: revert "mm: fix-up zone present pages"

    Revert

    commit 7f1290f2f2a4d2c3f1b7ce8e87256e052ca23125
    Author: Jianguo Wu <wujianguo@huawei.com>
    AuthorDate: Mon Oct 8 16:33:06 2012 -0700
    Commit: Linus Torvalds <torvalds@linux-foundation.org>
    CommitDate: Tue Oct 9 16:22:54 2012 +0900

    mm: fix-up zone present pages


    That patch tried to fix a issue when calculating zone->present_pages, but
    it caused a regression on 32bit systems with HIGHMEM. With that
    changeset, reset_zone_present_pages() resets all zone->present_pages to
    zero, and fixup_zone_present_pages() is called to recalculate
    zone->present_pages when the boot allocator frees core memory pages into
    buddy allocator. Because highmem pages are not freed by bootmem
    allocator, all highmem zones' present_pages becomes zero.

    Various options for improving the situation are being discussed but for
    now, let's return to the 3.6 code.

    Cc: Jianguo Wu <wujianguo@huawei.com>
    Cc: Jiang Liu <jiang.liu@huawei.com>
    Cc: Petr Tesarik <ptesarik@suse.cz>
    Cc: "Luck, Tony" <tony.luck@intel.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: Minchan Kim <minchan.kim@gmail.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: David Rientjes <rientjes@google.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    ---

    arch/ia64/mm/init.c | 1 -
    include/linux/mm.h | 4 ----
    mm/bootmem.c | 10 +---------
    mm/memory_hotplug.c | 7 -------
    mm/nobootmem.c | 3 ---
    mm/page_alloc.c | 34 ----------------------------------
    6 files changed, 1 insertion(+), 58 deletions(-)

    diff -puN arch/ia64/mm/init.c~revert-1 arch/ia64/mm/init.c
    --- a/arch/ia64/mm/init.c~revert-1
    +++ a/arch/ia64/mm/init.c
    @@ -637,7 +637,6 @@ mem_init (void)

    high_memory = __va(max_low_pfn * PAGE_SIZE);

    - reset_zone_present_pages();
    for_each_online_pgdat(pgdat)
    if (pgdat->bdata->node_bootmem_map)
    totalram_pages += free_all_bootmem_node(pgdat);
    diff -puN include/linux/mm.h~revert-1 include/linux/mm.h
    --- a/include/linux/mm.h~revert-1
    +++ a/include/linux/mm.h
    @@ -1684,9 +1684,5 @@ static inline unsigned int debug_guardpa
    static inline bool page_is_guard(struct page *page) { return false; }
    #endif /* CONFIG_DEBUG_PAGEALLOC */

    -extern void reset_zone_present_pages(void);
    -extern void fixup_zone_present_pages(int nid, unsigned long start_pfn,
    - unsigned long end_pfn);
    -
    #endif /* __KERNEL__ */
    #endif /* _LINUX_MM_H */
    diff -puN mm/bootmem.c~revert-1 mm/bootmem.c
    --- a/mm/bootmem.c~revert-1
    +++ a/mm/bootmem.c
    @@ -198,8 +198,6 @@ static unsigned long __init free_all_boo
    int order = ilog2(BITS_PER_LONG);

    __free_pages_bootmem(pfn_to_page(start), order);
    - fixup_zone_present_pages(page_to_nid(pfn_to_page(start)),
    - start, start + BITS_PER_LONG);
    count += BITS_PER_LONG;
    start += BITS_PER_LONG;
    } else {
    @@ -210,9 +208,6 @@ static unsigned long __init free_all_boo
    if (vec & 1) {
    page = pfn_to_page(start + off);
    __free_pages_bootmem(page, 0);
    - fixup_zone_present_pages(
    - page_to_nid(page),
    - start + off, start + off + 1);
    count++;
    }
    vec >>= 1;
    @@ -226,11 +221,8 @@ static unsigned long __init free_all_boo
    pages = bdata->node_low_pfn - bdata->node_min_pfn;
    pages = bootmem_bootmap_pages(pages);
    count += pages;
    - while (pages--) {
    - fixup_zone_present_pages(page_to_nid(page),
    - page_to_pfn(page), page_to_pfn(page) + 1);
    + while (pages--)
    __free_pages_bootmem(page++, 0);
    - }

    bdebug("nid=%td released=%lx\n", bdata - bootmem_node_data, count);

    diff -puN mm/memory_hotplug.c~revert-1 mm/memory_hotplug.c
    --- a/mm/memory_hotplug.c~revert-1
    +++ a/mm/memory_hotplug.c
    @@ -106,7 +106,6 @@ static void get_page_bootmem(unsigned lo
    void __ref put_page_bootmem(struct page *page)
    {
    unsigned long type;
    - struct zone *zone;

    type = (unsigned long) page->lru.next;
    BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
    @@ -117,12 +116,6 @@ void __ref put_page_bootmem(struct page
    set_page_private(page, 0);
    INIT_LIST_HEAD(&page->lru);
    __free_pages_bootmem(page, 0);
    -
    - zone = page_zone(page);
    - zone_span_writelock(zone);
    - zone->present_pages++;
    - zone_span_writeunlock(zone);
    - totalram_pages++;
    }

    }
    diff -puN mm/nobootmem.c~revert-1 mm/nobootmem.c
    --- a/mm/nobootmem.c~revert-1
    +++ a/mm/nobootmem.c
    @@ -116,8 +116,6 @@ static unsigned long __init __free_memor
    return 0;

    __free_pages_memory(start_pfn, end_pfn);
    - fixup_zone_present_pages(pfn_to_nid(start >> PAGE_SHIFT),
    - start_pfn, end_pfn);

    return end_pfn - start_pfn;
    }
    @@ -128,7 +126,6 @@ unsigned long __init free_low_memory_cor
    phys_addr_t start, end, size;
    u64 i;

    - reset_zone_present_pages();
    for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL)
    count += __free_memory_core(start, end);

    diff -puN mm/page_alloc.c~revert-1 mm/page_alloc.c
    --- a/mm/page_alloc.c~revert-1
    +++ a/mm/page_alloc.c
    @@ -6098,37 +6098,3 @@ void dump_page(struct page *page)
    dump_page_flags(page->flags);
    mem_cgroup_print_bad_page(page);
    }
    -
    -/* reset zone->present_pages */
    -void reset_zone_present_pages(void)
    -{
    - struct zone *z;
    - int i, nid;
    -
    - for_each_node_state(nid, N_HIGH_MEMORY) {
    - for (i = 0; i < MAX_NR_ZONES; i++) {
    - z = NODE_DATA(nid)->node_zones + i;
    - z->present_pages = 0;
    - }
    - }
    -}
    -
    -/* calculate zone's present pages in buddy system */
    -void fixup_zone_present_pages(int nid, unsigned long start_pfn,
    - unsigned long end_pfn)
    -{
    - struct zone *z;
    - unsigned long zone_start_pfn, zone_end_pfn;
    - int i;
    -
    - for (i = 0; i < MAX_NR_ZONES; i++) {
    - z = NODE_DATA(nid)->node_zones + i;
    - zone_start_pfn = z->zone_start_pfn;
    - zone_end_pfn = zone_start_pfn + z->spanned_pages;
    -
    - /* if the two regions intersect */
    - if (!(zone_start_pfn >= end_pfn || zone_end_pfn <= start_pfn))
    - z->present_pages += min(end_pfn, zone_end_pfn) -
    - max(start_pfn, zone_start_pfn);
    - }
    -}
    _


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