kernel/vm: Introduce VMCache::CanOvercommit().

Allows the Anonymous caches to report overcommitting status.

headers/private/kernel/vm/VMCache.h

@@ -149,6 +149,7 @@ public:
 									{ return fRefCount; }
 
 	// backing store operations
+	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
 	virtual	bool				HasPage(off_t offset);
 

src/system/kernel/vm/VMAnonymousCache.cpp

@@ -738,6 +738,13 @@ VMAnonymousCache::Commit(off_t size, int priority)
 }
 
 
+bool
+VMAnonymousCache::CanOvercommit()
+{
+	return fCanOvercommit;
+}
+
+
 bool
 VMAnonymousCache::HasPage(off_t offset)
 {

src/system/kernel/vm/VMAnonymousCache.h

@@ -49,6 +49,7 @@ public:
 
 	virtual	status_t			Discard(off_t offset, off_t size);
 
+	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
 	virtual	bool				HasPage(off_t offset);
 	virtual	bool				DebugHasPage(off_t offset);

src/system/kernel/vm/VMAnonymousNoSwapCache.cpp

@@ -94,6 +94,13 @@ VMAnonymousNoSwapCache::Commit(off_t size, int priority)
 }
 
 
+bool
+VMAnonymousNoSwapCache::CanOvercommit()
+{
+	return fCanOvercommit;
+}
+
+
 bool
 VMAnonymousNoSwapCache::HasPage(off_t offset)
 {

src/system/kernel/vm/VMAnonymousNoSwapCache.h

@@ -22,6 +22,7 @@ public:
 									int32 numGuardPages,
 									uint32 allocationFlags);
 
+	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
 	virtual	bool				HasPage(off_t offset);
 

src/system/kernel/vm/VMCache.cpp

@@ -1298,6 +1298,13 @@ VMCache::FlushAndRemoveAllPages()
 }
 
 
+bool
+VMCache::CanOvercommit()
+{
+	return false;
+}
+
+
 status_t
 VMCache::Commit(off_t size, int priority)
 {