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    Subject[PATCH 4/8] proc: export more page flags in /proc/kpageflags
    Export all page flags faithfully in /proc/kpageflags.

    11. KPF_MMAP (pseudo flag) memory mapped page
    12. KPF_ANON (pseudo flag) memory mapped page (anonymous)
    13. KPF_SWAPCACHE page is in swap cache
    14. KPF_SWAPBACKED page is swap/RAM backed
    15. KPF_COMPOUND_HEAD (*)
    16. KPF_COMPOUND_TAIL (*)
    17. KPF_HUGE hugeTLB pages
    18. KPF_UNEVICTABLE page is in the unevictable LRU list
    19. KPF_HWPOISON(TBD) hardware detected corruption
    20. KPF_NOPAGE (pseudo flag) no page frame at the address
    32-39. more obscure flags for kernel developers

    (*) For compound pages, exporting _both_ head/tail info enables
    users to tell where a compound page starts/ends, and its order.

    The acompanied page-types tool will handle the details like decoupling
    overloaded flags and hiding obscure flags to normal users.

    Thanks to KOSAKI and Andi for their valuable recommendations!

    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Matt Mackall <mpm@selenic.com>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    fs/proc/page.c | 148 +++++++++++++++++++++++++++++++++++++----------
    1 file changed, 118 insertions(+), 30 deletions(-)

    --- linux.orig/fs/proc/page.c
    +++ linux/fs/proc/page.c
    @@ -71,19 +71,124 @@ static const struct file_operations proc

    /* These macros are used to decouple internal flags from exported ones */

    -#define KPF_LOCKED 0
    -#define KPF_ERROR 1
    -#define KPF_REFERENCED 2
    -#define KPF_UPTODATE 3
    -#define KPF_DIRTY 4
    -#define KPF_LRU 5
    -#define KPF_ACTIVE 6
    -#define KPF_SLAB 7
    -#define KPF_WRITEBACK 8
    -#define KPF_RECLAIM 9
    -#define KPF_BUDDY 10
    +#define KPF_LOCKED 0
    +#define KPF_ERROR 1
    +#define KPF_REFERENCED 2
    +#define KPF_UPTODATE 3
    +#define KPF_DIRTY 4
    +#define KPF_LRU 5
    +#define KPF_ACTIVE 6
    +#define KPF_SLAB 7
    +#define KPF_WRITEBACK 8
    +#define KPF_RECLAIM 9
    +#define KPF_BUDDY 10
    +
    +/* 11-20: new additions in 2.6.31 */
    +#define KPF_MMAP 11
    +#define KPF_ANON 12
    +#define KPF_SWAPCACHE 13
    +#define KPF_SWAPBACKED 14
    +#define KPF_COMPOUND_HEAD 15
    +#define KPF_COMPOUND_TAIL 16
    +#define KPF_HUGE 17
    +#define KPF_UNEVICTABLE 18
    +#define KPF_NOPAGE 20
    +
    +/* kernel hacking assistances
    + * WARNING: subject to change, never rely on them!
    + */
    +#define KPF_RESERVED 32
    +#define KPF_MLOCKED 33
    +#define KPF_MAPPEDTODISK 34
    +#define KPF_PRIVATE 35
    +#define KPF_PRIVATE_2 36
    +#define KPF_OWNER_PRIVATE 37
    +#define KPF_ARCH 38
    +#define KPF_UNCACHED 39

    -#define kpf_copy_bit(flags, dstpos, srcpos) (((flags >> srcpos) & 1) << dstpos)
    +static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
    +{
    + return ((kflags >> kbit) & 1) << ubit;
    +}
    +
    +static u64 get_uflags(struct page *page)
    +{
    + u64 k;
    + u64 u;
    +
    + /*
    + * pseudo flag: KPF_NOPAGE
    + * it differentiates a memory hole from a page with no flags
    + */
    + if (!page)
    + return 1 << KPF_NOPAGE;
    +
    + k = page->flags;
    + u = 0;
    +
    + /*
    + * pseudo flags for the well known (anonymous) memory mapped pages
    + *
    + * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
    + * simple test in page_mapped() is not enough.
    + */
    + if (!PageSlab(page) && page_mapped(page))
    + u |= 1 << KPF_MMAP;
    + if (PageAnon(page))
    + u |= 1 << KPF_ANON;
    +
    + /*
    + * compound pages: export both head/tail info
    + * they together define a compound page's start/end pos and order
    + */
    + if (PageHead(page))
    + u |= 1 << KPF_COMPOUND_HEAD;
    + if (PageTail(page))
    + u |= 1 << KPF_COMPOUND_TAIL;
    + if (PageHuge(page))
    + u |= 1 << KPF_HUGE;
    +
    + u |= kpf_copy_bit(k, KPF_LOCKED, PG_locked);
    +
    + /*
    + * Caveats on high order pages:
    + * PG_buddy will only be set on the head page; SLUB/SLQB do the same
    + * for PG_slab; SLOB won't set PG_slab at all on compound pages.
    + */
    + u |= kpf_copy_bit(k, KPF_SLAB, PG_slab);
    + u |= kpf_copy_bit(k, KPF_BUDDY, PG_buddy);
    +
    + u |= kpf_copy_bit(k, KPF_ERROR, PG_error);
    + u |= kpf_copy_bit(k, KPF_DIRTY, PG_dirty);
    + u |= kpf_copy_bit(k, KPF_UPTODATE, PG_uptodate);
    + u |= kpf_copy_bit(k, KPF_WRITEBACK, PG_writeback);
    +
    + u |= kpf_copy_bit(k, KPF_LRU, PG_lru);
    + u |= kpf_copy_bit(k, KPF_REFERENCED, PG_referenced);
    + u |= kpf_copy_bit(k, KPF_ACTIVE, PG_active);
    + u |= kpf_copy_bit(k, KPF_RECLAIM, PG_reclaim);
    +
    + u |= kpf_copy_bit(k, KPF_SWAPCACHE, PG_swapcache);
    + u |= kpf_copy_bit(k, KPF_SWAPBACKED, PG_swapbacked);
    +
    +#ifdef CONFIG_UNEVICTABLE_LRU
    + u |= kpf_copy_bit(k, KPF_UNEVICTABLE, PG_unevictable);
    + u |= kpf_copy_bit(k, KPF_MLOCKED, PG_mlocked);
    +#endif
    +
    +#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
    + u |= kpf_copy_bit(k, KPF_UNCACHED, PG_uncached);
    +#endif
    +
    + u |= kpf_copy_bit(k, KPF_RESERVED, PG_reserved);
    + u |= kpf_copy_bit(k, KPF_MAPPEDTODISK, PG_mappedtodisk);
    + u |= kpf_copy_bit(k, KPF_PRIVATE, PG_private);
    + u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2);
    + u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
    + u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1);
    +
    + return u;
    +};

    static ssize_t kpageflags_read(struct file *file, char __user *buf,
    size_t count, loff_t *ppos)
    @@ -93,7 +198,6 @@ static ssize_t kpageflags_read(struct fi
    unsigned long src = *ppos;
    unsigned long pfn;
    ssize_t ret = 0;
    - u64 kflags, uflags;

    pfn = src / KPMSIZE;
    count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
    @@ -105,24 +209,8 @@ static ssize_t kpageflags_read(struct fi
    ppage = pfn_to_page(pfn);
    else
    ppage = NULL;
    - if (!ppage)
    - kflags = 0;
    - else
    - kflags = ppage->flags;
    -
    - uflags = kpf_copy_bit(kflags, KPF_LOCKED, PG_locked) |
    - kpf_copy_bit(kflags, KPF_ERROR, PG_error) |
    - kpf_copy_bit(kflags, KPF_REFERENCED, PG_referenced) |
    - kpf_copy_bit(kflags, KPF_UPTODATE, PG_uptodate) |
    - kpf_copy_bit(kflags, KPF_DIRTY, PG_dirty) |
    - kpf_copy_bit(kflags, KPF_LRU, PG_lru) |
    - kpf_copy_bit(kflags, KPF_ACTIVE, PG_active) |
    - kpf_copy_bit(kflags, KPF_SLAB, PG_slab) |
    - kpf_copy_bit(kflags, KPF_WRITEBACK, PG_writeback) |
    - kpf_copy_bit(kflags, KPF_RECLAIM, PG_reclaim) |
    - kpf_copy_bit(kflags, KPF_BUDDY, PG_buddy);

    - if (put_user(uflags, out)) {
    + if (put_user(get_uflags(ppage), out)) {
    ret = -EFAULT;
    break;
    }
    --



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