xref: /illumos-gate/usr/src/man/man9f/devfs_clean.9f (revision bbf21555)

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.\" Copyright 2016 Nexenta Systems, Inc.
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.Dd July 26, 2016
.Dt DEVFS_CLEAN 9F
.Os
.Sh NAME
.Nm devfs_clean
.Nd destroy unreferenced devfs nodes and detach devices
.Sh SYNOPSIS
.In sys/fs/dv_node.h
.Ft int
.Fo devfs_clean
.Fa "dev_info_t *dip"
.Fa "char *devnm"
.Fa "uint_t flags"
.Fc
.Sh INTERFACE LEVEL
.Sy Volatile -
private DDI function
.Pp
This is a private function that is not part of the stable DDI.
It may be removed or changed at any time.
.Sh PARAMETERS
.Bl -tag -width Ds
.It Va dip
A pointer to the device's
.Vt dev_info
structure.
Clean up is rooted at this device.
.It Va devnm
An optional character string used to restrict the devfs nodes list.
.It Va flags
The following flag is supported:
.Bl -tag -width "DV_CLEAN_FORCE"
.It Sy DV_CLEAN_FORCE
force clean of referenced directories, referenced empty directories are marked
as stale to facilitate DR
.Pq dynamic reconfiguration
.El
.El
.Sh DESCRIPTION
The
.Fn devfs_clean
function is used to clean up and detach devices from the system.
While many device drivers may have one or more minor nodes created with
.Xr ddi_create_minor_node 9F ,
some device drivers may have children devices with different device drivers
attached.
Each of these entries shows up in the file system of the global zone under
.Pa /devices
.Po see
.Xr devfs 4FS
.Pc .
These nodes are referred to as a devfs nodes
.Pq Vt dv_node .
.Pp
.Nm devfs
caches unreferenced devfs nodes to speed up the performance of
.Nm ls ,
.Nm find ,
etc.
The
.Fn devfs_clean
function is used to cleanup cached nodes to reclaim memory as well as to
facilitate device removal
.Pq devfs nodes reference dev_info nodes, which prevents driver from detaching .
.Pp
The
.Fn devfs_clean
function starts searching the tree rooted at
.Va dip .
All directories encountered are recursed through.
If
.Va devnm
is not NULL, then it is used to limit the nodes that it searches.
It compares the name of the node, ignoring any part of the device's name that
corresponds to a minor node.
If
.Va devnm
has been specified, then cleanup stops immediately after a busy devfs node has
been encountered.
.Pp
Not all nodes may be cleaned up when a driver calls the
.Fn devfs_clean
function.
However, this is a non-fatal situation.
Callers should continue trying to offline devices as many holds from userland
processes may exist due to device contracts which will be released when the
device is offlined.
.Pp
If a shell parks in a
.Pa /devices
directory, the devfs node will be held, preventing the corresponding device to
be detached.
This would be a denial of service against DR (dynamic reconfiguration).
To prevent this, DR code calls
.Fn devfs_clean
with the
.Sy DV_CLEAN_FORCE
flag.
.Sh CONTEXT
This function may be called in user or kernel context.
.Sh RETURN VALUES
The
.Fn devfs_clean
function always succeeds and returns zero.
.Sh SEE ALSO
.Xr devfs 4FS