Merge patch series "exportfs: Some kernel-doc fixes"

A file system implementation declares that instances of the filesystem

are exportable by setting the s_export_op field in the struct

super_block.  This field must point to a "struct export_operations"

struct which has the following members:

  encode_fh (mandatory)

    Takes a dentry and creates a filehandle fragment which may later be used

    to find or create a dentry for the same object.

  fh_to_dentry (mandatory)

    Given a filehandle fragment, this should find the implied object and

    create a dentry for it (possibly with d_obtain_alias).

  fh_to_parent (optional but strongly recommended)

    Given a filehandle fragment, this should find the parent of the

    implied object and create a dentry for it (possibly with

    d_obtain_alias).  May fail if the filehandle fragment is too small.

  get_parent (optional but strongly recommended)

    When given a dentry for a directory, this should return  a dentry for

    the parent.  Quite possibly the parent dentry will have been allocated

    by d_alloc_anon.  The default get_parent function just returns an error

    so any filehandle lookup that requires finding a parent will fail.

    ->lookup("..") is *not* used as a default as it can leave ".." entries

    in the dcache which are too messy to work with.

  get_name (optional)

    When given a parent dentry and a child dentry, this should find a name

    in the directory identified by the parent dentry, which leads to the

    object identified by the child dentry.  If no get_name function is

    supplied, a default implementation is provided which uses vfs_readdir

    to find potential names, and matches inode numbers to find the correct

    match.

  flags

    Some filesystems may need to be handled differently than others. The

    export_operations struct also includes a flags field that allows the

    filesystem to communicate such information to nfsd. See the Export

    Operations Flags section below for more explanation.

super_block.  This field must point to a struct export_operations

which has the following members:

.. kernel-doc:: include/linux/exportfs.h

   :identifiers: struct export_operations

A filehandle fragment consists of an array of 1 or more 4byte words,

together with a one byte "type".

 * @commit_metadata: commit metadata changes to stable storage

 *

 * See Documentation/filesystems/nfs/exporting.rst for details on how to use

 * this interface correctly.

 * this interface correctly and the definition of the flags.

 *

 * encode_fh:

 * @encode_fh:

 *    @encode_fh should store in the file handle fragment @fh (using at most

 *    @max_len bytes) information that can be used by @decode_fh to recover the

 *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit

 *    greater than @max_len*4 bytes). On error @max_len contains the minimum

 *    size(in 4 byte unit) needed to encode the file handle.

 *

 * fh_to_dentry:

 * @fh_to_dentry:

 *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle

 *    fragment (@fh, @fh_len). It should return a &struct dentry which refers

 *    to the same file that the file handle fragment refers to.  If it cannot,

 *    created with d_alloc_root.  The caller can then find any other extant

 *    dentries by following the d_alias links.

 *

 * fh_to_parent:

 * @fh_to_parent:

 *    Same as @fh_to_dentry, except that it returns a pointer to the parent

 *    dentry if it was encoded into the filehandle fragment by @encode_fh.

 *

 * get_name:

 * @get_name:

 *    @get_name should find a name for the given @child in the given @parent

 *    directory.  The name should be stored in the @name (with the

 *    understanding that it is already pointing to a %NAME_MAX + 1 sized

 *    buffer.   get_name() should return %0 on success, a negative error code

 *    or error.  @get_name will be called without @parent->i_rwsem held.

 *

 * get_parent:

 * @get_parent:

 *    @get_parent should find the parent directory for the given @child which

 *    is also a directory.  In the event that it cannot be found, or storage

 *    space cannot be allocated, a %ERR_PTR should be returned.

 *

 * permission:

 * @permission:

 *    Allow filesystems to specify a custom permission function.

 *

 * open:

 * @open:

 *    Allow filesystems to specify a custom open function.

 *

 * commit_metadata:

 * @commit_metadata:

 *    @commit_metadata should commit metadata changes to stable storage.

 *

 * @get_uuid:

 *    Get a filesystem unique signature exposed to clients.

 *

 * @map_blocks:

 *    Map and, if necessary, allocate blocks for a layout.

 *

 * @commit_blocks:

 *    Commit blocks in a layout once the client is done with them.

 *

 * @flags:

 *    Allows the filesystem to communicate to nfsd that it may want to do things

 *    differently when dealing with it.

 *

 * Locking rules:

 *    get_parent is called with child->d_inode->i_rwsem down

 *    get_name is not (which is possibly inconsistent)