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.\" by Gregory McGarry.
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.Dd April 17, 2017
.Dt VFSSUBR 9
.Os
.Sh NAME
.Nm vfssubr ,
.Nm vfs_getnewfsid ,
.Nm vfs_getvfs ,
.Nm vfs_export ,
.Nm vfs_showexport ,
.Nm vfs_export_lookup ,
.Nm vfs_setpublicfs ,
.Nm vfs_mountedon ,
.Nm vfs_mountroot ,
.Nm vfs_unmountall ,
.Nm vfs_busy ,
.Nm vfs_unbusy ,
.Nm vfs_mountalloc ,
.Nm vfs_rootmountalloc ,
.Nm vfs_shutdown ,
.Nm vfs_attach ,
.Nm vfs_detach ,
.Nm vfs_reinit ,
.Nm vfs_getopsbyname ,
.Nm vfs_suspend ,
.Nm vfs_resume ,
.Nm vfs_vnode_iterator_init ,
.Nm vfs_vnode_iterator_destroy ,
.Nm vfs_vnode_iterator_next
.Nd high-level interface to kernel file system interface
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.In sys/vnode.h
.Ft void
.Fn vfs_getnewfsid "struct mount *mp"
.Ft struct mount *
.Fn vfs_getvfs "fsid_t *fsid"
.Ft int
.Fn vfs_export_lookup "struct mount *mp" "struct netexport *nep" \
"struct export_args *argp"
.Ft int
.Fn vfs_setpublicfs "struct mount *mp" "struct netexport *nep" \
"struct export_args *argp"
.Ft int
.Fn vfs_mountedon "struct vnode *vp"
.Ft int
.Fn vfs_mountroot "void"
.Ft void
.Fn vfs_unmountall  "struct lwp *l"
.Ft int
.Fn vfs_busy "struct mount *mp"
.Ft void
.Fn vfs_unbusy "struct mount *mp"
.Ft struct mount *
.Fn vfs_mountalloc "struct vfsops *vfs" "struct vnode *vp"
.Ft int
.Fn vfs_rootmountalloc "char *fstypename" "char *devname" \
"struct mount **mpp"
.Ft void
.Fn vfs_shutdown "void"
.Ft int
.Fn vfs_attach "struct vfsops *vfs"
.Ft int
.Fn vfs_detach "struct vfsops *vfs"
.Ft void
.Fn vfs_reinit "void"
.Ft struct vfsops *
.Fn vfs_getopsbyname "const char *name"
.Ft int
.Fn vfs_suspend "struct mount *mp" "int nowait"
.Ft void
.Fn vfs_resume "struct mount *mp"
.Ft void
.Fn vfs_vnode_iterator_init "struct mount *mp" "struct vnode_iterator **vip"
.Ft void
.Fn vfs_vnode_iterator_destroy "struct vnode_iterator *vi"
.Ft struct vnode *
.Fn vfs_vnode_iterator_next "struct vnode_iterator *vi" "bool (*selector)(void *context, struct vnode *vpp)" "void *context"
.Sh DESCRIPTION
The high-level functions described in this page are the interface to
the kernel file system interface (VFS).
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn vfs_getnewfsid "mp"
Get a new unique file system id type for the file system specified by
the mount structure
.Fa mp .
The file system id type is stored in
.Em mp-\*[Gt]mnt_stat.f_fsidx .
.It Fn vfs_getvfs "fsid"
Lookup a mount point with the file system identifier
.Fa fsid .
.It Fn vfs_export_lookup "mp" "nep" "argp"
Check client permission on the exportable file system specified by the
mount structure
.Fa mp .
The argument
.Fa nam
is the address of the networked client.
This function is used by file system type specific functions to verify
that the client can access the file system.
.It Fn vfs_setpublicfs "mp" "nep" "argp"
Set the publicly exported file system specified by the mount structure
.Fa mp .
.It Fn vfs_mountedon "vp"
Check to see if a file system is mounted on a block device specified
by the vnode
.Fa vp .
.It Fn vfs_mountroot "void"
Mount the root file system.
.It Fn vfs_unmountall "l"
Unmount all file systems.
.It Fn vfs_busy "mp"
Mark the mount point specified by
.Fa mp
as busy and get a reference to it.
This function is used to synchronize access and to delay unmounting.
The caller must hold a pre-existing reference to the mount.
.It Fn vfs_unbusy "mp"
Undo a
.Fn vfs_busy
on the mount point specified by
.Fa mp .
.It Fn vfs_mountalloc "vfsops" "vp"
Allocate and initialise a mount structure, setting
.Em mnt_vnodecovered
to
.Fa vp
and
.Em mnt_op
to
.Fa vfsops .
On success return the address of the mount structure.
Otherwise, return
.Dv NULL .
.It Fn vfs_rootmountalloc "fstypename" "devname" "mpp"
Lookup a file system type specified by the name
.Fa fstypename
and if found allocate and initialise a mount structure for it.
The allocated mount structure is marked as busy and returned in the
address specified by
.Fa mpp .
The device the root file system was mounted from is specified by the
argument
.Fa devname
and is recorded in the new mount structure.
.It Fn vfs_shutdown
Sync and unmount all file systems before shutting down.
Invoked by
.Xr cpu_reboot 9 .
.It Fn vfs_attach "vfs"
Establish file system
.Fa vfs
and initialise it.
.It Fn vfs_detach "vfs"
Remove file system
.Fa vfs
from the kernel.
.It Fn vfs_reinit "void"
Reinitialises all file systems within the kernel through file
system-specific vfs operation (see
.Xr vfsops 9 ) .
.It Fn vfs_getopsbyname "name"
Given a file system name specified by
.Fa name ,
look up the vfs operations for that file system (see
.Xr vfsops 9 ) ,
or return
.Dv NULL
if file system isn't present in the kernel.
.It Fn vfs_suspend "mp" "nowait"
Request a mounted file system to suspend all operations.
All new operations to the file system are stopped.
After all operations in progress have completed, the
file system is synced to disk and the function returns.
If a file system suspension is currently in progress and
.Fa nowait
is set
.Er EWOULDBLOCK
is returned.
If the operation is successful, zero is returned, otherwise an
appropriate error code is returned.
.It Fn vfs_resume "mp"
Request a mounted file system to resume operations.
.It Fn vfs_vnode_iterator_init "mp" "vip"
Allocate and initialize an iterator
.Fa vip
over all vnodes attached to mount point
.Fa mp .
.It Fn vfs_vnode_iterator_destroy "vi"
Free all resources associated with an iterator
.Fa vi .
.It Fn vfs_vnode_iterator_next "vi" "selector" "context"
Return the next vnode from iterator
.Fa vi .
If the operation is successful the vnode has a reference added to it
and it is returned.
If the iterator is exhausted the function returns
.Dv NULL .
If an optional
.Fa selector
function is provided, then this function is called with the
.Fa context
provided and the candidate vnode to be returned.
If the
.Fa selector
returns
.Dv false ,
then the vnode is skipped; if it returns
.Dv true ,
the vnode is referenced and then returned.
.El
.Sh CODE REFERENCES
The vfs interface functions are implemented within the files
.Pa sys/kern/vfs_mount.c ,
.Pa sys/kern/vfs_subr.c
and
.Pa sys/kern/vfs_init.c .
.Sh SEE ALSO
.Xr intro 9 ,
.Xr namei 9 ,
.Xr vfs 9 ,
.Xr vfsops 9 ,
.Xr vnode 9 ,
.Xr vnodeops 9