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authorru <ru@FreeBSD.org>2004-07-02 21:45:06 +0000
committerru <ru@FreeBSD.org>2004-07-02 21:45:06 +0000
commit46fddaa54b09baa407fa66a14d46c0cc3a906e60 (patch)
tree602e903272257a1c5b455a48800dcaa680741026 /sbin/mount_nullfs
parent20fbd172b22ab587e9d796f4cb8664a235cebe78 (diff)
downloadFreeBSD-src-46fddaa54b09baa407fa66a14d46c0cc3a906e60.zip
FreeBSD-src-46fddaa54b09baa407fa66a14d46c0cc3a906e60.tar.gz
Mechanically kill hard sentence breaks.
Diffstat (limited to 'sbin/mount_nullfs')
-rw-r--r--sbin/mount_nullfs/mount_nullfs.840
1 files changed, 27 insertions, 13 deletions
diff --git a/sbin/mount_nullfs/mount_nullfs.8 b/sbin/mount_nullfs/mount_nullfs.8
index 43534f0..03060de 100644
--- a/sbin/mount_nullfs/mount_nullfs.8
+++ b/sbin/mount_nullfs/mount_nullfs.8
@@ -103,7 +103,8 @@ The
.Nm
utility takes two arguments, the pathname
of the lower vfs (target-pn) and the pathname where the null
-layer will appear in the namespace (mount-point-pn). After
+layer will appear in the namespace (mount-point-pn).
+After
the null layer is put into place, the contents
of target-pn subtree will be aliased under mount-point-pn.
.\"
@@ -111,15 +112,19 @@ of target-pn subtree will be aliased under mount-point-pn.
.Sh OPERATION OF A NULL LAYER
The null layer is the minimum file system layer,
simply bypassing all possible operations to the lower layer
-for processing there. The majority of its activity centers
+for processing there.
+The majority of its activity centers
on the bypass routine, through which nearly all vnode operations
pass.
.Pp
The bypass routine accepts arbitrary vnode operations for
-handling by the lower layer. It begins by examining vnode
+handling by the lower layer.
+It begins by examining vnode
operation arguments and replacing any null-nodes by their
-lower-layer equivalents. It then invokes the operation
-on the lower layer. Finally, it replaces the null-nodes
+lower-layer equivalents.
+It then invokes the operation
+on the lower layer.
+Finally, it replaces the null-nodes
in the arguments and, if a vnode is returned by the operation,
stacks a null-node on top of the returned vnode.
.Pp
@@ -144,11 +149,13 @@ information.
.\"
.Sh INSTANTIATING VNODE STACKS
Mounting associates the null layer with a lower layer,
-in effect stacking two VFSes. Vnode stacks are instead
+in effect stacking two VFSes.
+Vnode stacks are instead
created on demand as files are accessed.
.Pp
The initial mount creates a single vnode stack for the
-root of the new null layer. All other vnode stacks
+root of the new null layer.
+All other vnode stacks
are created as a result of vnode operations on
this or other null vnode stacks.
.Pp
@@ -168,7 +175,8 @@ the root null-node (which was created when the null layer was mounted).
Now consider opening
.Pa sys .
A vop_lookup would be
-done on the root null-node. This operation would bypass through
+done on the root null-node.
+This operation would bypass through
to the lower layer which would return a vnode representing
the UFS
.Pa sys .
@@ -197,8 +205,10 @@ null layer.
.\"
.Sh INVOKING OPERATIONS ON LOWER LAYERS
There are two techniques to invoke operations on a lower layer
-when the operation cannot be completely bypassed. Each method
-is appropriate in different situations. In both cases,
+when the operation cannot be completely bypassed.
+Each method
+is appropriate in different situations.
+In both cases,
it is the responsibility of the aliasing layer to make
the operation arguments "correct" for the lower layer
by mapping a vnode argument to the lower layer.
@@ -217,7 +227,8 @@ the lower layer with the
.Em VOP_OPERATIONNAME
interface.
The advantage of this method is that it is easy to invoke
-arbitrary operations on the lower layer. The disadvantage
+arbitrary operations on the lower layer.
+The disadvantage
is that vnode arguments must be manually mapped.
.\"
.\"
@@ -228,8 +239,11 @@ UCLA Technical Report CSD-910056,
.Em "Stackable Layers: an Architecture for File System Development" .
.Sh BUGS
THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK)
-AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT YOUR
-OWN RISK. BEWARE OF DOG. SLIPPERY WHEN WET.
+AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM.
+USE AT YOUR
+OWN RISK.
+BEWARE OF DOG.
+SLIPPERY WHEN WET.
.Pp
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