diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/netfs_library.rst | 37 |
1 files changed, 18 insertions, 19 deletions
diff --git a/Documentation/filesystems/netfs_library.rst b/Documentation/filesystems/netfs_library.rst index a80a59941d2f..3276c3d55142 100644 --- a/Documentation/filesystems/netfs_library.rst +++ b/Documentation/filesystems/netfs_library.rst @@ -37,30 +37,31 @@ The network filesystem helper library needs a place to store a bit of state for its use on each netfs inode it is helping to manage. To this end, a context structure is defined:: - struct netfs_i_context { + struct netfs_inode { + struct inode inode; const struct netfs_request_ops *ops; - struct fscache_cookie *cache; + struct fscache_cookie *cache; }; -A network filesystem that wants to use netfs lib must place one of these -directly after the VFS ``struct inode`` it allocates, usually as part of its -own struct. This can be done in a way similar to the following:: +A network filesystem that wants to use netfs lib must place one of these in its +inode wrapper struct instead of the VFS ``struct inode``. This can be done in +a way similar to the following:: struct my_inode { - struct { - /* These must be contiguous */ - struct inode vfs_inode; - struct netfs_i_context netfs_ctx; - }; + struct netfs_inode netfs; /* Netfslib context and vfs inode */ ... }; -This allows netfslib to find its state by simple offset from the inode pointer, -thereby allowing the netfslib helper functions to be pointed to directly by the -VFS/VM operation tables. +This allows netfslib to find its state by using ``container_of()`` from the +inode pointer, thereby allowing the netfslib helper functions to be pointed to +directly by the VFS/VM operation tables. The structure contains the following fields: + * ``inode`` + + The VFS inode structure. + * ``ops`` The set of operations provided by the network filesystem to netfslib. @@ -78,14 +79,12 @@ To help deal with the per-inode context, a number helper functions are provided. Firstly, a function to perform basic initialisation on a context and set the operations table pointer:: - void netfs_i_context_init(struct inode *inode, - const struct netfs_request_ops *ops); + void netfs_inode_init(struct inode *inode, + const struct netfs_request_ops *ops); -then two functions to cast between the VFS inode structure and the netfs -context:: +then a function to cast from the VFS inode structure to the netfs context:: - struct netfs_i_context *netfs_i_context(struct inode *inode); - struct inode *netfs_inode(struct netfs_i_context *ctx); + struct netfs_inode *netfs_node(struct inode *inode); and finally, a function to get the cache cookie pointer from the context attached to an inode (or NULL if fscache is disabled):: |