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 accompanying 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!

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
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>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 120 insertions, 32 deletions

diff --git a/fs/proc/page.c b/fs/proc/page.c
index e73e911b7d0c..9d926bd279a4 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -72,19 +72,124 @@ static const struct file_operations proc_kpagecount_operations = {
 
 /* 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_copy_bit(flags, dstpos, srcpos) (((flags >> srcpos) & 1) << dstpos)
+#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
+
+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)
@@ -94,7 +199,6 @@ static ssize_t kpageflags_read(struct file *file, char __user *buf,
         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);
@@ -106,24 +210,8 @@ static ssize_t kpageflags_read(struct file *file, char __user *buf,
                         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;
                 }