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author | ru <ru@FreeBSD.org> | 2004-07-02 21:45:06 +0000 |
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committer | ru <ru@FreeBSD.org> | 2004-07-02 21:45:06 +0000 |
commit | 46fddaa54b09baa407fa66a14d46c0cc3a906e60 (patch) | |
tree | 602e903272257a1c5b455a48800dcaa680741026 /sbin/mount_nullfs | |
parent | 20fbd172b22ab587e9d796f4cb8664a235cebe78 (diff) | |
download | FreeBSD-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.8 | 40 |
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 This code also needs an owner in order to be less dangerous - serious hackers can apply by sending mail to |