Merge branch 'x86-pat-for-linus' of git://git.kernel.org/pub/scm/linu…

…x/kernel/git/tip/linux-2.6-tip

* 'x86-pat-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, pat: Update the page flags for memtype atomically instead of using memtype_lock
  x86, pat: In rbt_memtype_check_insert(), update new->type only if valid
  x86, pat: Migrate to rbtree only backend for pat memtype management
  x86, pat: Preparatory changes in pat.c for bigger rbtree change
  rbtree: Add support for augmented rbtrees

Documentation/rbtree.txt

@@ -190,3 +190,61 @@ Example:
   for (node = rb_first(&mytree); node; node = rb_next(node))
 	printk("key=%s\n", rb_entry(node, struct mytype, node)->keystring);
 
+Support for Augmented rbtrees
+-----------------------------
+
+Augmented rbtree is an rbtree with "some" additional data stored in each node.
+This data can be used to augment some new functionality to rbtree.
+Augmented rbtree is an optional feature built on top of basic rbtree
+infrastructure. rbtree user who wants this feature will have an augment
+callback function in rb_root initialized.
+
+This callback function will be called from rbtree core routines whenever
+a node has a change in one or both of its children. It is the responsibility
+of the callback function to recalculate the additional data that is in the
+rb node using new children information. Note that if this new additional
+data affects the parent node's additional data, then callback function has
+to handle it and do the recursive updates.
+
+
+Interval tree is an example of augmented rb tree. Reference -
+"Introduction to Algorithms" by Cormen, Leiserson, Rivest and Stein.
+More details about interval trees:
+
+Classical rbtree has a single key and it cannot be directly used to store
+interval ranges like [lo:hi] and do a quick lookup for any overlap with a new
+lo:hi or to find whether there is an exact match for a new lo:hi.
+
+However, rbtree can be augmented to store such interval ranges in a structured
+way making it possible to do efficient lookup and exact match.
+
+This "extra information" stored in each node is the maximum hi
+(max_hi) value among all the nodes that are its descendents. This
+information can be maintained at each node just be looking at the node
+and its immediate children. And this will be used in O(log n) lookup
+for lowest match (lowest start address among all possible matches)
+with something like:
+
+find_lowest_match(lo, hi, node)
+{
+	lowest_match = NULL;
+	while (node) {
+		if (max_hi(node->left) > lo) {
+			// Lowest overlap if any must be on left side
+			node = node->left;
+		} else if (overlap(lo, hi, node)) {
+			lowest_match = node;
+			break;
+		} else if (lo > node->lo) {
+			// Lowest overlap if any must be on right side
+			node = node->right;
+		} else {
+			break;
+		}
+	}
+	return lowest_match;
+}
+
+Finding exact match will be to first find lowest match and then to follow
+successor nodes looking for exact match, until the start of a node is beyond
+the hi value we are looking for.

arch/x86/include/asm/cacheflush.h

@@ -44,9 +44,6 @@ static inline void copy_from_user_page(struct vm_area_struct *vma,
 	memcpy(dst, src, len);
 }
 
-#define PG_WC				PG_arch_1
-PAGEFLAG(WC, WC)
-
 #ifdef CONFIG_X86_PAT
 /*
  * X86 PAT uses page flags WC and Uncached together to keep track of
@@ -55,42 +52,51 @@ PAGEFLAG(WC, WC)
  * _PAGE_CACHE_UC_MINUS and fourth state where page's memory type has not
  * been changed from its default (value of -1 used to denote this).
  * Note we do not support _PAGE_CACHE_UC here.
- *
- * Caller must hold memtype_lock for atomicity.
  */
+
+#define _PGMT_DEFAULT		0
+#define _PGMT_WC		(1UL << PG_arch_1)
+#define _PGMT_UC_MINUS		(1UL << PG_uncached)
+#define _PGMT_WB		(1UL << PG_uncached | 1UL << PG_arch_1)
+#define _PGMT_MASK		(1UL << PG_uncached | 1UL << PG_arch_1)
+#define _PGMT_CLEAR_MASK	(~_PGMT_MASK)
+
 static inline unsigned long get_page_memtype(struct page *pg)
 {
-	if (!PageUncached(pg) && !PageWC(pg))
+	unsigned long pg_flags = pg->flags & _PGMT_MASK;
+
+	if (pg_flags == _PGMT_DEFAULT)
 		return -1;
-	else if (!PageUncached(pg) && PageWC(pg))
+	else if (pg_flags == _PGMT_WC)
 		return _PAGE_CACHE_WC;
-	else if (PageUncached(pg) && !PageWC(pg))
+	else if (pg_flags == _PGMT_UC_MINUS)
 		return _PAGE_CACHE_UC_MINUS;
 	else
 		return _PAGE_CACHE_WB;
 }
 
 static inline void set_page_memtype(struct page *pg, unsigned long memtype)
 {
+	unsigned long memtype_flags = _PGMT_DEFAULT;
+	unsigned long old_flags;
+	unsigned long new_flags;
+
 	switch (memtype) {
 	case _PAGE_CACHE_WC:
-		ClearPageUncached(pg);
-		SetPageWC(pg);
+		memtype_flags = _PGMT_WC;
 		break;
 	case _PAGE_CACHE_UC_MINUS:
-		SetPageUncached(pg);
-		ClearPageWC(pg);
+		memtype_flags = _PGMT_UC_MINUS;
 		break;
 	case _PAGE_CACHE_WB:
-		SetPageUncached(pg);
-		SetPageWC(pg);
-		break;
-	default:
-	case -1:
-		ClearPageUncached(pg);
-		ClearPageWC(pg);
+		memtype_flags = _PGMT_WB;
 		break;
 	}
+
+	do {
+		old_flags = pg->flags;
+		new_flags = (old_flags & _PGMT_CLEAR_MASK) | memtype_flags;
+	} while (cmpxchg(&pg->flags, old_flags, new_flags) != old_flags);
 }
 #else
 static inline unsigned long get_page_memtype(struct page *pg) { return -1; }

arch/x86/mm/Makefile

@@ -6,6 +6,7 @@ nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_physaddr.o		:= $(nostackp)
 CFLAGS_setup_nx.o		:= $(nostackp)
 
+obj-$(CONFIG_X86_PAT)		+= pat_rbtree.o
 obj-$(CONFIG_SMP)		+= tlb.o
 
 obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o