Lines Matching full:layer

39  * Null Layer
43  * The null layer duplicates a portion of the filesystem
48  * all lower-layer vnodes, not just over directory vnodes.
50  * The null layer has two purposes.  First, it serves as a demonstration
51  * of layering by proving a layer which does nothing.  (It actually
53  * more than nothing.)  Second, the null layer can serve as a prototype
54  * layer.  Since it provides all necessary layer framework,
56  * with a null layer.
58  * The remainder of this man page examines the null layer as a basis
67  * layer will appear in the namespace (alias-pn).  After
68  * the null layer is put into place, the contents
72  * OPERATION OF A NULL LAYER
74  * The null layer is the minimum filesystem layer,
75  * simply bypassing all possible operations to the lower layer
81  * handling by the lower layer.  It begins by examining vnode
83  * lower-layer equivlants.  It then invokes the operation
84  * on the lower layer.  Finally, it replaces the null-nodes
94  * they can handle freeing null-layer specific data. Vop_print
102  * the necessary locking at their layer.
107  * Mounting associates the null layer with a lower layer,
112  * root of the new null layer.  All other vnode stacks
121  * For example, imagine mounting a null layer with
122  * "mount_nullfs /usr/include /dev/layer/null".
123  * Changing directory to /dev/layer/null will assign
124  * the root null-node (which was created when the null layer was mounted).
127  * to the lower layer which would return a vnode representing
137  * a copy of the null layer, rename all files and variables, and
141  * The umap layer is an example of a layer descended from the
142  * null layer.
147  * There are two techniques to invoke operations on a lower layer
150  * it is the responsibility of the aliasing layer to make
151  * the operation arguments "correct" for the lower layer
152  * by mapping a vnode arguments to the lower layer.
154  * The first approach is to call the aliasing layer's bypass routine.
156  * currently being handled on the lower layer.  It has the advantage
158  * An example of this is null_getattrs in the null layer.
161  * the lower layer with the VOP_OPERATIONNAME interface.
163  * arbitrary operations on the lower layer.  The disadvantage
285 	 * Call the operation on the lower layer
338 	 * (Assumes that the lower layer always returns
379  * We have to carry on the locking protocol on the null layer vnodes
381  * if this layer is mounted read-only.
495  * Setattr call. Disallow write attempts if the layer is mounted read-only.
756 	 * If we're still active we must ask the lower layer to
834  * Do not allow the VOP_INACTIVE to be passed to the lower layer,