* VMCache::Resize(): Corrected TODO comment.

* Changed the semantics of VMCache::HasPage(). It was interpreted
  inconsistently by the derived classes. Now it returns whether the backing
  store can provide the page (via Read()). The default implementation returns
  false. VNodeCache::HasPage() only returns true, if the given offset is
  within the cache (i.e. file) bounds. This prevents vm_soft_fault() from
  adding clean pages to vnode caches on faults beyond the file bounds.
  Probably fixes #5473 -- at least mmap_resize_test behaves correctly, now.
* Removed redundant HasPage() and Fault() overrides in VMCache derived
  classes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36374 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/cache/vnode_store.cpp

@@ -36,10 +36,8 @@ VMVnodeCache::Init(struct vnode *vnode, uint32 allocationFlags)
 bool
 VMVnodeCache::HasPage(off_t offset)
 {
-	// We always pretend to have the page - even if it's beyond the size of
+	return ROUNDUP(offset, B_PAGE_SIZE) >= virtual_base
-	// the file. The read function will only cut down the size of the read,
+		&& offset < virtual_end;
-	// it won't fail because of that.
-	return true;
 }
 
 
@@ -103,6 +101,10 @@ VMVnodeCache::WriteAsync(off_t offset, const iovec* vecs, size_t count,
 status_t
 VMVnodeCache::Fault(struct VMAddressSpace *aspace, off_t offset)
 {
+	if (!HasPage(offset))
+		return B_BAD_ADDRESS;
+
+	// vm_soft_fault() reads the page in.
 	return B_BAD_HANDLER;
 }
 

src/system/kernel/vm/VMCache.cpp

@@ -1078,8 +1078,9 @@ VMCache::Resize(off_t newSize, int priority)
 			DEBUG_PAGE_ACCESS_START(page);
 			vm_remove_all_page_mappings(page);
 			ASSERT(page->wired_count == 0);
-				// TODO: Find a real solution! Unmapping is probably fine, but
+				// TODO: Find a real solution! If the page is wired
-				// we have no way of unmapping wired pages here.
+				// temporarily (e.g. by lock_memory()), we actually must not
+				// unmap it!
 			RemovePage(page);
 			vm_page_free(this, page);
 				// Note: When iterating through a IteratableSplayTree
@@ -1145,10 +1146,19 @@ VMCache::Commit(off_t size, int priority)
 }
 
 
+/*!	Returns whether the cache's underlying backing store could deliver the
+	page at the given offset.
+
+	Basically it returns whether a Read() at \a offset would at least read a
+	partial page (assuming that no unexpected errors occur or the situation
+	changes in the meantime).
+*/
 bool
 VMCache::HasPage(off_t offset)
 {
-	return offset >= virtual_base && offset <= virtual_end;
+	// In accordance with Fault() the default implementation doesn't have a
+	// backing store and doesn't allow faults.
+	return false;
 }
 
 

src/system/kernel/vm/VMDeviceCache.cpp

@@ -6,6 +6,7 @@
  * Distributed under the terms of the NewOS License.
  */
 
+
 #include "VMDeviceCache.h"
 
 
@@ -17,14 +18,6 @@ VMDeviceCache::Init(addr_t baseAddress, uint32 allocationFlags)
 }
 
 
-bool
-VMDeviceCache::HasPage(off_t offset)
-{
-	// this should never be called
-	return false;
-}
-
-
 status_t
 VMDeviceCache::Read(off_t offset, const iovec *vecs, size_t count,
 	uint32 flags, size_t *_numBytes)
@@ -41,10 +34,3 @@ VMDeviceCache::Write(off_t offset, const iovec *vecs, size_t count,
 	// no place to write, this will cause the page daemon to skip this store
 	return B_OK;
 }
-
-
-status_t
-VMDeviceCache::Fault(struct VMAddressSpace* addressSpace, off_t offset)
-{
-	return B_BAD_ADDRESS;
-}

src/system/kernel/vm/VMDeviceCache.h

@@ -17,16 +17,11 @@ class VMDeviceCache : public VMCache {
 public:
 			status_t	Init(addr_t baseAddress, uint32 allocationFlags);
 
-	virtual	bool		HasPage(off_t offset);
-
 	virtual	status_t	Read(off_t offset, const iovec *vecs, size_t count,
 							uint32 flags, size_t *_numBytes);
 	virtual	status_t	Write(off_t offset, const iovec *vecs, size_t count,
 							uint32 flags, size_t *_numBytes);
 
-	virtual	status_t			Fault(struct VMAddressSpace* addressSpace,
-									off_t offset);
-
 private:
 	addr_t	fBaseAddress;
 };

src/system/kernel/vm/VMNullCache.cpp

@@ -3,6 +3,7 @@
  * Distributed under the terms of the MIT License.
  */
 
+
 #include "VMNullCache.h"
 
 
@@ -11,10 +12,3 @@ VMNullCache::Init(uint32 allocationFlags)
 {
 	return VMCache::Init(CACHE_TYPE_NULL, allocationFlags);
 }
-
-
-status_t
-VMNullCache::Fault(struct VMAddressSpace* addressSpace, off_t offset)
-{
-	return B_BAD_ADDRESS;
-}

src/system/kernel/vm/VMNullCache.h

@@ -16,9 +16,6 @@
 class VMNullCache : public VMCache {
 public:
 			status_t			Init(uint32 allocationFlags);
-
-	virtual	status_t			Fault(struct VMAddressSpace* addressSpace,
-									off_t offset);
 };