sdev_vnops.c revision 9e5aa9d8a21f8efa8ba9c9e4a0aa6edc66d07eb2
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
*/
/*
* Copyright (c) 2013, Joyent, Inc. All rights reserved.
*/
/*
* vnode ops for the /dev filesystem
*
* - VDIR, VCHR, CBLK, and VLNK are considered must supported files
* - VREG and VDOOR are used for some internal implementations in
* the global zone, e.g. devname and devfsadm communication
* - other file types are unusual in this namespace and
* not supported for now
*/
/*
* sdev has a few basic goals:
* o Provide /dev for the global zone as well as various non-global zones.
* o Provide the basic functionality that devfsadm might need (mknod,
* symlinks, etc.)
* o Allow persistent permissions on files in /dev.
* o Allow for dynamic directories and nodes for use by various services (pts,
* zvol, net, etc.)
*
* The sdev file system is primarily made up of sdev_node_t's which is sdev's
* counterpart to the vnode_t. There are two different classes of sdev_node_t's
* that we generally care about, dynamic and otherwise.
*
* Persisting Information
* ----------------------
*
* When sdev is mounted, it keeps track of the underlying file system it is
* mounted over. In certain situations, sdev will go and create entries in that
* underlying file system. These underlying 'back end' nodes are used as proxies
* for various changes in permissions. While specific sets of nodes, such as
* dynamic ones, are exempt, this process stores permission changes against
* these back end nodes. The point of all of this is to allow for these settings
* to persist across host and zone reboots. As an example, consider the entry
* changing the permissions on c0t0d0 you'd have the following logical
* relationships:
*
* +------------------+ sdev_vnode +--------------+
* | sdev_node_t |<---------------->| vnode_t |
* +------------------+ +--------------+
* |
* | sdev_attrvp
* |
* | +---------------------+
* +--->| vnode_t for UFS|ZFS |
* +---------------------+
*
* sdev is generally in memory. Therefore when a lookup happens and there is no
* entry already inside of a directory cache, it will next check the backing
* store. If the backing store exists, we will reconstitute the sdev_node based
* on the information that we persisted. When we create the backing store node,
* we use the struct vattr information that we already have in sdev_node_t.
* Because of this, we already know if the entry was previously a symlink,
* directory, or some other kind of type. Note that not all types of nodes are
* supported. Currently only VDIR, VCHR, VBLK, VREG, VDOOR, and VLNK are
* eligible to be persisted.
*
* When the sdev_node is created and the lookup is done, we grab a hold on the
* underlying vnode as part of the call to VOP_LOOKUP. That reference is held
* until the sdev_node becomes inactive. Once its reference count reaches one
* and the VOP_INACTIVE callback fires leading to the destruction of the node,
* the reference on the underlying vnode will be released.
*
* The backing store node will be deleted only when the node itself is deleted
* through the means of a VOP_REMOVE, VOP_RMDIR, or similar call.
*
* Not everything can be persisted, see The Rules section for more details.
*
* Dynamic Nodes
* -------------
*
* Dynamic nodes allow for specific interactions with various kernel subsystems
* when looking up directory entries. This allows the lookup and readdir
* functions to check against the kernel subsystem's for validity. eg. does a
* zvol or nic still exist.
*
* More specifically, when we create various directories we check if the
* directory name matches that of one of the names in the vtab[] (sdev_subr.c).
* If it does, we swap out the vnode operations into a new set which combine the
* normal sdev vnode operations with the dynamic set here.
*
* In addition, various dynamic nodes implement a verification entry point. This
* verification entry is used as a part of lookup and readdir. The goal for
* these dynamic nodes is to allow them to check with the underlying subsystems
* to ensure that these devices are still present, or if they have gone away, to
* remove them from the results. This is indicated by using the SDEV_VTOR flag
* in vtab[].
*
* Dynamic nodes have additional restrictions placed upon them. They may only
* appear at the top level directory of the file system. In addition, users
* cannot create dirents below any leve of a dynamic node aside from its special
* vnops.
*
* Profiles
* --------
*
* Profiles exist for the purpose of non-global zones. They work with the zone
* brands and zoneadmd to set up a filter of allowed devices that can appear in
* a non-global zone's /dev. These are sent to sdev by means of libdevinfo and a
* modctl system call. Specifically it allows one to add patterns of device
* paths to include and exclude. It allows for a collection of symlinks to be
* added and it allows for remapping names.
*
* When operating in a non-global zone, several of the sdev vnops are redirected
* to the profile versions. These impose additional restrictions such as
* enforcing that a non-global zone's /dev is read only.
*
* sdev_node_t States
* ------------------
*
* A given sdev_node_t has a field called the sdev_state which describes where
* in the sdev life cycle it is. There are three primary states: SDEV_INIT,
* SDEV_READY, and SDEV_ZOMBIE.
*
* SDEV_INIT: When a new /dev file is first looked up, a sdev_node
* is allocated, initialized and added to the directory's
* sdev_node cache. A node at this state will also
* have the SDEV_LOOKUP flag set.
*
* Other threads that are trying to look up a node at
* this state will be blocked until the SDEV_LOOKUP flag
* is cleared.
*
* When the SDEV_LOOKUP flag is cleared, the node may
* transition into the SDEV_READY state for a successful
* lookup or the node is removed from the directory cache
* and destroyed if the named node can not be found.
* An ENOENT error is returned for the second case.
*
* SDEV_READY: A /dev file has been successfully looked up and
* associated with a vnode. The /dev file is available
* for the supported /dev file system operations.
*
* SDEV_ZOMBIE: Deletion of a /dev file has been explicitly issued
* to an SDEV_READY node. The node is transitioned into
* the SDEV_ZOMBIE state if the vnode reference count
* is still held. A SDEV_ZOMBIE node does not support
* any of the /dev file system operations. A SDEV_ZOMBIE
* node is immediately removed from the directory cache
* and destroyed once the reference count reaches zero.
*
* Historically nodes that were marked SDEV_ZOMBIE were not removed from the
* underlying directory caches. This has been the source of numerous bugs and
* thus to better mimic what happens on a real file system, it is no longer the
* case.
*
* The following state machine describes the life cycle of a given node and its
* associated states:
*
* node is . . . . .
* allocated via . +-------------+ . . . . . . . vnode_t refcount
* sdev_nodeinit() . | Unallocated | . reaches zero and
* +--------*-----| Memory |<--------*---+ sdev_inactive is
* | +-------------+ | called.
* | +------------^ | called.
* v | |
* +-----------+ * . . sdev_nodeready() +-------------+
* | SDEV_INIT | | or related setup | SDEV_ZOMBIE |
* +-----------+ | failure +-------------+
* | | ^
* | | +------------+ |
* +-*----------->| SDEV_READY |--------*-----+
* . +------------+ . The node is no longer
* . . node successfully . . . . . valid or we've been
* inserted into the asked to remove it.
* directory cache This happens via
* and sdev_nodready() sdev_dirdelete().
* call successful.
*
* Adding and Removing Dirents, Zombie Nodes
* -----------------------------------------
*
* As part of doing a lookup, readdir, or an explicit creation operation like
* mkdir or create, nodes may be created. Every directory has an avl tree which
* contains its children, the sdev_entries tree. This is only used if the type
* is VDIR. Access to this is controlled by the sdev_node_t's contents_lock and
* it is managed through sdev_cache_update().
*
* Every sdev_node_t has a field sdev_state, which describes the current state
* of the node. A node is generally speaking in the SDEV_READY state. When it is
* there, it can be looked up, accessed, and operations performed on it. When a
* node is going to be removed from the directory cache it is marked as a
* zombie. Once a node becomes a zombie, no other file system operations will
* succeed and it will continue to exist as a node until the vnode count on the
* node reaches zero. At that point, the node will be freed. However, once a
* node has been marked as a zombie, it will be removed immediately from the
* directory cache such that no one else may find it again. This means that
* someone else can insert a new entry into that directory with the same name
* and without a problem.
*
* To remove a node, see the section on that in The Rules.
*
* The Rules
* ---------
* These are the rules to live by when working in sdev. These are not
* exhaustive.
*
* - Set 1: Working with Backing Nodes
* o If there is a SDEV_READY sdev_node_t, it knows about its backing node.
* o If we find a backing node when looking up an sdev_node_t for the first
* time, we use its attributes to build our sdev_node_t.
* o If there is a found backing node, or we create a backing node, that's
* when we grab the hold on its vnode.
* o If we mark an sdev_node_t a ZOMBIE, we must remove its backing node from
* the underlying file system. It must not be searchable or findable.
* o We release our hold on the backing node vnode when we destroy the
* sdev_node_t.
*
* - Set 2: Locking rules for sdev (not exhaustive)
* o The majority of nodes contain an sdev_contents rw lock. You must hold it
* for read or write if manipulating its contents appropriately.
* o You must lock your parent before yourself.
* o If you need your vnode's v_lock and the sdev_contents rw lock, you must
* grab the v_lock before the sdev_contents rw_lock.
* o If you release a lock on the node as a part of upgrading it, you must
* verify that the node has not become a zombie as a part of this process.
*
* - Set 3: Zombie Status and What it Means
* o If you encounter a node that is a ZOMBIE, that means that it has been
* unlinked from the backing store.
* o If you release your contents lock and acquire it again (say as part of
* trying to grab a write lock) you must check that the node has not become
* a zombie.
* o You should VERIFY that a looked up node is not a zombie. This follows
* from the following logic. To mark something as a zombie means that it is
* removed from the parents directory cache. To do that, you must have a
* write lock on the parent's sdev_contents. To lookup through that
* directory you must have a read lock. This then becomes a simple ordering
* problem. If you've been granted the lock then the other operation cannot
* be in progress or must have already succeeded.
*
* - Set 4: Removing Directory Entries (aka making nodes Zombies)
* o Write lock must be held on the directory
* o Write lock must be held on the node
* o Remove the sdev_node_t from its parent cache
* o Remove the corresponding backing store node, if it exists, eg. use
* VOP_REMOVE or VOP_RMDIR.
* o You must NOT make any change in the vnode reference count! Nodes should
* only be cleaned up through VOP_INACTIVE callbacks.
* o VOP_INACTIVE is the only one responsible for doing the final vn_rele of
* the backing store vnode that was grabbed during lookup.
*
* - Set 5: What Nodes may be Persisted
* o The root, /dev is always persisted
* o Any node in vtab which is marked SDEV_DYNAMIC, may not be persisted
* unless it is also marked SDEV_PERSIST
* o Anything whose parent directory is marked SDEV_PERSIST will pass that
* along to the child as long as it does not contradict the above rules
*/
#include <sys/sysmacros.h>
#include <sys/vfs_opreg.h>
#include <sys/pathname.h>
/*ARGSUSED*/
static int
{
int error = 0;
return (0);
if (!SDEV_IS_GLOBAL(dv))
return (ENOTSUP);
return (ENOENT);
return (ENOTSUP);
return (ENOENT);
}
return (error);
}
/*ARGSUSED1*/
static int
{
return (0);
}
if (!SDEV_IS_GLOBAL(dv))
return (ENOTSUP);
return (ENOTSUP);
}
/*ARGSUSED*/
static int
struct caller_context *ct)
{
int error;
if (!SDEV_IS_GLOBAL(dv))
return (EINVAL);
return (EISDIR);
/* only supporting regular files in /dev */
return (EINVAL);
return (error);
}
/*ARGSUSED*/
static int
struct caller_context *ct)
{
int error = 0;
if (!SDEV_IS_GLOBAL(dv))
return (EINVAL);
return (EISDIR);
/* only supporting regular files in /dev */
return (EINVAL);
if (error == 0) {
AT_MTIME);
}
return (error);
}
/*ARGSUSED*/
static int
{
return (ENOTTY);
return (EINVAL);
}
static int
{
int error = 0;
/*
* search order:
* - for persistent nodes (SDEV_PERSIST): backstore
* - for non-persistent nodes: module ops if global, then memory
*/
if (dv->sdev_attrvp) {
} else {
}
return (error);
}
/*ARGSUSED4*/
static int
{
}
static int
{
int error;
/* return fs_fab_acl() if flavor matches, else do nothing */
return (ENOSYS);
}
return (error);
}
static int
{
int error;
return (0);
return (fs_nosys());
/*
* if coming in directly, the acl system call will
* have held the read-write lock via VOP_RWLOCK()
* If coming in via specfs, specfs will have
* held the rw lock on the realvp i.e. us.
*/
if (error) {
return (fs_nosys());
}
/* clean out the memory copy if any */
}
}
return (error);
}
int
{
int shift = 0;
shift += 3;
shift += 3;
}
}
static int
{
int ret = 0;
if (dv->sdev_attrvp) {
if (ret)
}
return (ret);
}
/*
* Lookup
*/
/*ARGSUSED3*/
static int
{
int error;
/* execute access is required to search the directory */
return (error);
if (!SDEV_IS_GLOBAL(parent))
}
/*ARGSUSED2*/
static int
{
int error = 0;
return (ENOTSUP);
return (ENOENT);
}
/* non-global do not allow pure node creation */
if (!SDEV_IS_GLOBAL(parent)) {
}
/* execute access is required to search the directory */
return (error);
/* check existing name */
/* XXXci - We may need to translate the C-I flags on VOP_LOOKUP */
/* name found */
if (error == 0) {
} else {
}
if (error) {
return (error);
}
/* truncation first */
if (error) {
return (error);
}
}
return (0);
}
/* bail out early */
return (error);
/* verify write access - compliance specifies ENXIO */
return (error);
}
/*
* For memory-based (ROFS) directory:
* - either disallow node creation;
* - or implement VOP_CREATE of its own
*/
if (!SDEV_IS_PERSIST(parent)) {
return (ENOTSUP);
}
cred, SDEV_READY);
if (error) {
if (self)
return (error);
}
/* take care the timestamps for the node and its parent */
if (SDEV_IS_GLOBAL(parent))
/* wake up other threads blocked on looking up this node */
return (error);
}
static int
{
int error;
int len;
int bkstore;
/* bail out early */
if (nm[0] == '.') {
if (len == 1) {
return (EINVAL);
return (EEXIST);
}
}
if (!SDEV_IS_GLOBAL(parent)) {
return (ENOTSUP);
}
/* execute access is required to search the directory */
return (error);
}
/* check existence first */
return (ENOENT);
}
return (ENOENT);
}
/* write access is required to remove an entry */
return (error);
}
/* Make sure we didn't become a zombie */
return (ENOENT);
}
}
/* we do not support unlinking a non-empty directory */
return (EBUSY);
}
/*
* sdev_dirdelete does the real job of:
* - make sure no open ref count
* - destroying the sdev_node
* - releasing the hold on attrvp
*/
/*
* best efforts clean up the backing store
*/
if (bkstore) {
/*
* do not report BUSY error
* because the backing store ref count is released
* when the last ref count on the sdev_node is
* released.
*/
sdcmn_err2(("sdev_remove: device %s is still on"
error = 0;
}
}
return (error);
}
/*
* Some restrictions for this file system:
* - both oldnm and newnm are in the scope of /dev file system,
* to simply the namespace management model.
*/
/*ARGSUSED6*/
static int
{
int samedir = 0; /* set if odvp == ndvp */
int error = 0;
int bkstore = 0;
/* prevent modifying "." and ".." */
if ((onm[0] == '.' &&
(nnm[0] == '.' &&
return (EINVAL);
}
/* ZOMBIE parent doesn't allow new node creation */
return (ENOENT);
}
/* renaming only supported for global device nodes */
if (!SDEV_IS_GLOBAL(fromparent)) {
return (ENOTSUP);
}
return (ENOENT);
}
/*
* acquire the global lock to prevent
*/
/* check existence of the source node */
/* XXXci - We may need to translate the C-I flags on VOP_LOOKUP */
if (error) {
sdcmn_err2(("sdev_rename: the source node %s exists\n",
onm));
return (error);
}
}
/* check existence of destination */
/* XXXci - We may need to translate the C-I flags on VOP_LOOKUP */
return (error);
}
}
/*
* make sure the source and the destination are
* in the same dev filesystem
*/
return (error);
}
return (error);
}
return (EXDEV);
}
}
/* make sure the old entry can be deleted */
if (error) {
return (error);
}
/* make sure the destination allows creation */
if (!samedir) {
if (error) {
return (error);
}
}
/* destination file exists */
}
return (EACCES);
}
/*
* link source to new target in the memory. Regardless of failure, we
* must rele our hold on nvp.
*/
if (error) {
sdcmn_err2(("sdev_rename: renaming %s to %s failed "
return (error);
}
/*
* unlink from source
*/
sdcmn_err2(("sdev_rename: the source is deleted already\n"));
return (0);
}
sdcmn_err2(("sdev_rename: the source is being deleted\n"));
return (0);
}
/* clean out the directory contents before it can be removed */
sdcmn_err2(("sdev_rename: cleandir finished with %d\n",
error));
error = 0;
}
/* best effforts clean up the backing store */
if (bkstore) {
/* XXXci - We may need to translate the C-I flags on VOP_REMOVE */
} else {
/* XXXci - We may need to translate the C-I flags on VOP_RMDIR */
}
if (error) {
sdcmn_err2(("sdev_rename: device %s is "
"still on disk %s\n", onm,
fromparent->sdev_path));
error = 0;
}
}
/* once reached to this point, the rename is regarded successful */
return (0);
}
/*
* dev-fs version of "ln -s path dev-name"
* tnm - path, e.g. /devices/... or /dev/...
* lnm - dev_name
*/
/*ARGSUSED6*/
static int
{
int error;
sdcmn_err2(("sdev_symlink: parent %s is ZOMBIED \n",
return (ENOENT);
}
if (!SDEV_IS_GLOBAL(parent)) {
return (ENOTSUP);
}
/* execute access is required to search a directory */
return (error);
/* find existing name */
/* XXXci - We may need to translate the C-I flags here */
if (error == 0) {
return (EEXIST);
}
return (error);
/* write access is required to create a symlink */
return (error);
/* put it into memory cache */
cred, SDEV_READY);
if (error) {
if (self)
return (error);
}
/* take care the timestamps for the node and its parent */
if (SDEV_IS_GLOBAL(parent))
/* wake up other threads blocked on looking up this node */
return (0);
}
/*ARGSUSED6*/
static int
{
int error;
return (ENOENT);
}
/* non-global do not allow pure directory creation */
if (!SDEV_IS_GLOBAL(parent)) {
}
/* execute access is required to search the directory */
return (error);
}
/* find existing name */
/* XXXci - We may need to translate the C-I flags on VOP_LOOKUP */
if (error == 0) {
return (EEXIST);
}
return (error);
/* require write access to create a directory */
return (error);
}
/* put it into memory */
if (error) {
if (self)
return (error);
}
/* take care the timestamps for the node and its parent */
if (SDEV_IS_GLOBAL(parent))
/* wake up other threads blocked on looking up this node */
return (0);
}
/*
* allowing removing an empty directory under /dev
*/
/*ARGSUSED*/
static int
{
int error = 0;
/* bail out early */
return (EINVAL);
return (EEXIST); /* should be ENOTEMPTY */
/* no destruction of non-global node */
if (!SDEV_IS_GLOBAL(parent)) {
return (ENOTSUP);
}
/* execute access is required to search the directory */
return (error);
/* check existing name */
return (ENOENT);
}
return (ENOENT);
}
/* some sanity checks */
return (EINVAL);
}
return (ENOTDIR);
}
if (vn_vfswlock(vp)) {
return (EBUSY);
}
return (EBUSY);
}
/* bail out on a non-empty directory */
return (ENOTEMPTY);
}
/* unlink it from the directory cache */
/* best effort to clean up the backing store */
if (SDEV_IS_PERSIST(parent)) {
if (error)
sdcmn_err2(("sdev_rmdir: cleaning device %s is on"
error = 0;
}
return (error);
}
/*
* read the contents of a symbolic link
*/
static int
{
int error = 0;
if (dv->sdev_attrvp) {
/* non-NULL attrvp implys a persisted node at READY state */
/* memory nodes, e.g. local nodes */
return (error);
}
return (ENOENT);
}
/*ARGSUSED4*/
static int
{
int error;
/*
* We must check that we have execute access to search the directory --
* but because our sdev_contents lock is already held as a reader (the
* caller must have done a VOP_RWLOCK()), we call directly into the
* underlying access routine if sdev_attr is non-NULL.
*/
return (EACCES);
} else {
return (error);
}
if (!SDEV_IS_GLOBAL(parent))
}
/*ARGSUSED1*/
static void
{
}
/*ARGSUSED2*/
static int
{
return (ENOSPC);
}
return (0);
}
/*
* This pair of routines bracket all VOP_READ, VOP_WRITE
* and VOP_READDIR requests. The contents lock stops things
* moving around while we're looking at them.
*/
/*ARGSUSED2*/
static int
{
}
/*ARGSUSED1*/
static void
{
}
/*ARGSUSED1*/
static int
{
}
/*ARGSUSED1*/
static int
{
int error;
return (error);
}
static int
{
switch (cmd) {
case _PC_ACL_ENABLED:
return (0);
}
}
const fs_operation_def_t sdev_vnodeops_tbl[] = {
};
int sdev_vnodeops_tbl_size = sizeof (sdev_vnodeops_tbl);