If we create new nodes or modify existing ones, especially directories, we must

ensure that these nodes are never put. As they keep all changes in memory,
putting them and consequently freeing them destroys the modifications without
a way to get them back from the underlaying filesystem. In case a created node
was put but still had its entry in the parent directory this could also lead
to the situation where an invalid node was requested from the underlaying
filesystem, leading to #4347.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@32815 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/file_systems/layers/write_overlay/write_overlay.cpp

@@ -103,12 +103,14 @@ public:
 		status_t			InitCheck();
 
 		bool				IsVirtual() { return fIsVirtual; }
+		bool				IsModified() { return fIsModified; }
 
 		fs_volume *			Volume() { return fVolume->Volume(); }
 		fs_volume *			SuperVolume() { return fVolume->SuperVolume(); }
 		fs_vnode *			SuperVnode() { return &fSuperVnode; }
 		ino_t				InodeNumber() { return fInodeNumber; }
 
+		void				SetModified();
 		void				CreateCache();
 
 		void				SetParentDir(OverlayInode *parentDir);
@@ -167,6 +169,7 @@ private:
 		bool				fHasStat;
 		bool				fHasDirents;
 		bool				fIsVirtual;
+		bool				fIsModified;
 		void *				fFileCache;
 };
 
@@ -202,6 +205,7 @@ OverlayInode::OverlayInode(OverlayVolume *volume, fs_vnode *superVnode,
 		fHasStat(false),
 		fHasDirents(false),
 		fIsVirtual(superVnode == NULL),
+		fIsModified(false),
 		fFileCache(NULL)
 {
 	TRACE("inode created %lld\n", fInodeNumber);
@@ -252,6 +256,19 @@ OverlayInode::InitCheck()
 }
 
 
+void
+OverlayInode::SetModified()
+{
+	// we must ensure that a modified node never get's put, as we cannot get it
+	// from the underlying filesystem, so we get an additional reference here
+	// and deliberately leak it
+	// TODO: what about non-force unmounting then?
+	void *unused = NULL;
+	get_vnode(Volume(), fInodeNumber, &unused);
+	fIsModified = true;
+}
+
+
 void
 OverlayInode::CreateCache()
 {
@@ -297,6 +314,8 @@ void
 OverlayInode::SetName(const char *name)
 {
 	fName = name;
+	if (!fIsModified)
+		SetModified();
 }
 
 
@@ -370,6 +389,9 @@ OverlayInode::WriteStat(const struct stat *stat, uint32 statMask)
 		statMask |= B_STAT_MODIFICATION_TIME;
 	}
 
+	if (!fIsModified)
+		SetModified();
+
 	notify_stat_changed(SuperVolume()->id, fInodeNumber, statMask);
 	return B_OK;
 }
@@ -422,8 +444,11 @@ OverlayInode::Open(int openMode, void **_cookie)
 		fOriginalNodeLength = stat.st_size;
 	}
 
-	if (openMode & O_TRUNC)
+	if (openMode & O_TRUNC) {
 		fStat.st_size = 0;
+		if (!fIsModified)
+			SetModified();
+	}
 
 	openMode &= ~(O_RDWR | O_WRONLY | O_TRUNC | O_CREAT);
 	status_t result = fSuperVnode.ops->open(SuperVolume(), &fSuperVnode,
@@ -557,6 +582,9 @@ OverlayInode::Write(void *_cookie, off_t position, const void *buffer,
 			position = fStat.st_size;
 	}
 
+	if (!fIsModified)
+		SetModified();
+
 	// find insertion point
 	write_buffer **link = &fWriteBuffers;
 	write_buffer *other = fWriteBuffers;
@@ -787,6 +815,10 @@ OverlayInode::AddEntry(overlay_dirent *entry)
 
 	fDirents = newDirents;
 	fDirents[fDirentCount++] = entry;
+
+	if (!fIsModified)
+		SetModified();
+
 	return B_OK;
 }
 
@@ -810,6 +842,9 @@ OverlayInode::RemoveEntry(const char *name, overlay_dirent **_entry)
 			else
 				entry->remove_and_dispose(Volume(), fInodeNumber);
 
+			if (!fIsModified)
+				SetModified();
+
 			return B_OK;
 		}
 	}
@@ -965,6 +1000,7 @@ OverlayInode::_CreateCommon(const char *name, int type, int perms,
 		return result;
 	}
 
+	node->SetModified();
 	node->CreateCache();
 
 	if (newInodeNumber != NULL)
@@ -998,7 +1034,8 @@ overlay_put_vnode(fs_volume *volume, fs_vnode *vnode, bool reenter)
 {
 	TRACE("put_vnode\n");
 	OverlayInode *node = (OverlayInode *)vnode->private_node;
-	if (node->IsVirtual()) {
+	if (node->IsVirtual() || node->IsModified()) {
+		panic("loosing virtual/modified node\n");
 		delete node;
 		return B_OK;
 	}