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vfs_vnode.c
2013 lines (1756 loc) · 50.8 KB
/
vfs_vnode.c
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/* $NetBSD: vfs_vnode.c,v 1.128 2021/10/20 03:08:18 thorpej Exp $ */
/*-
* Copyright (c) 1997-2011, 2019, 2020 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
* NASA Ames Research Center, by Charles M. Hannum, and by Andrew Doran.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vfs_subr.c 8.13 (Berkeley) 4/18/94
*/
/*
* The vnode cache subsystem.
*
* Life-cycle
*
* Normally, there are two points where new vnodes are created:
* VOP_CREATE(9) and VOP_LOOKUP(9). The life-cycle of a vnode
* starts in one of the following ways:
*
* - Allocation, via vcache_get(9) or vcache_new(9).
* - Reclamation of inactive vnode, via vcache_vget(9).
*
* Recycle from a free list, via getnewvnode(9) -> getcleanvnode(9)
* was another, traditional way. Currently, only the draining thread
* recycles the vnodes. This behaviour might be revisited.
*
* The life-cycle ends when the last reference is dropped, usually
* in VOP_REMOVE(9). In such case, VOP_INACTIVE(9) is called to inform
* the file system that vnode is inactive. Via this call, file system
* indicates whether vnode can be recycled (usually, it checks its own
* references, e.g. count of links, whether the file was removed).
*
* Depending on indication, vnode can be put into a free list (cache),
* or cleaned via vcache_reclaim, which calls VOP_RECLAIM(9) to
* disassociate underlying file system from the vnode, and finally
* destroyed.
*
* Vnode state
*
* Vnode is always in one of six states:
* - MARKER This is a marker vnode to help list traversal. It
* will never change its state.
* - LOADING Vnode is associating underlying file system and not
* yet ready to use.
* - LOADED Vnode has associated underlying file system and is
* ready to use.
* - BLOCKED Vnode is active but cannot get new references.
* - RECLAIMING Vnode is disassociating from the underlying file
* system.
* - RECLAIMED Vnode has disassociated from underlying file system
* and is dead.
*
* Valid state changes are:
* LOADING -> LOADED
* Vnode has been initialised in vcache_get() or
* vcache_new() and is ready to use.
* BLOCKED -> RECLAIMING
* Vnode starts disassociation from underlying file
* system in vcache_reclaim().
* RECLAIMING -> RECLAIMED
* Vnode finished disassociation from underlying file
* system in vcache_reclaim().
* LOADED -> BLOCKED
* Either vcache_rekey*() is changing the vnode key or
* vrelel() is about to call VOP_INACTIVE().
* BLOCKED -> LOADED
* The block condition is over.
* LOADING -> RECLAIMED
* Either vcache_get() or vcache_new() failed to
* associate the underlying file system or vcache_rekey*()
* drops a vnode used as placeholder.
*
* Of these states LOADING, BLOCKED and RECLAIMING are intermediate
* and it is possible to wait for state change.
*
* State is protected with v_interlock with one exception:
* to change from LOADING both v_interlock and vcache_lock must be held
* so it is possible to check "state == LOADING" without holding
* v_interlock. See vcache_get() for details.
*
* Reference counting
*
* Vnode is considered active, if reference count (vnode_t::v_usecount)
* is non-zero. It is maintained using: vref(9) and vrele(9), as well
* as vput(9), routines. Common points holding references are e.g.
* file openings, current working directory, mount points, etc.
*
* v_usecount is adjusted with atomic operations, however to change
* from a non-zero value to zero the interlock must also be held.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.128 2021/10/20 03:08:18 thorpej Exp $");
#ifdef _KERNEL_OPT
#include "opt_pax.h"
#endif
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/atomic.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/hash.h>
#include <sys/kauth.h>
#include <sys/kmem.h>
#include <sys/kthread.h>
#include <sys/module.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/pax.h>
#include <sys/syscallargs.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/vnode_impl.h>
#include <sys/wapbl.h>
#include <sys/fstrans.h>
#include <uvm/uvm.h>
#include <uvm/uvm_readahead.h>
#include <uvm/uvm_stat.h>
/* Flags to vrelel. */
#define VRELEL_ASYNC 0x0001 /* Always defer to vrele thread. */
#define LRU_VRELE 0
#define LRU_FREE 1
#define LRU_HOLD 2
#define LRU_COUNT 3
/*
* There are three lru lists: one holds vnodes waiting for async release,
* one is for vnodes which have no buffer/page references and one for those
* which do (i.e. v_holdcnt is non-zero). We put the lists into a single,
* private cache line as vnodes migrate between them while under the same
* lock (vdrain_lock).
*/
u_int numvnodes __cacheline_aligned;
static vnodelst_t lru_list[LRU_COUNT] __cacheline_aligned;
static kmutex_t vdrain_lock __cacheline_aligned;
static kcondvar_t vdrain_cv;
static int vdrain_gen;
static kcondvar_t vdrain_gen_cv;
static bool vdrain_retry;
static lwp_t * vdrain_lwp;
SLIST_HEAD(hashhead, vnode_impl);
static kmutex_t vcache_lock __cacheline_aligned;
static kcondvar_t vcache_cv;
static u_int vcache_hashsize;
static u_long vcache_hashmask;
static struct hashhead *vcache_hashtab;
static pool_cache_t vcache_pool;
static void lru_requeue(vnode_t *, vnodelst_t *);
static vnodelst_t * lru_which(vnode_t *);
static vnode_impl_t * vcache_alloc(void);
static void vcache_dealloc(vnode_impl_t *);
static void vcache_free(vnode_impl_t *);
static void vcache_init(void);
static void vcache_reinit(void);
static void vcache_reclaim(vnode_t *);
static void vrelel(vnode_t *, int, int);
static void vdrain_thread(void *);
static void vnpanic(vnode_t *, const char *, ...)
__printflike(2, 3);
/* Routines having to do with the management of the vnode table. */
extern struct mount *dead_rootmount;
extern int (**dead_vnodeop_p)(void *);
extern int (**spec_vnodeop_p)(void *);
extern struct vfsops dead_vfsops;
/*
* The high bit of v_usecount is a gate for vcache_tryvget(). It's set
* only when the vnode state is LOADED.
*/
#define VUSECOUNT_MASK 0x7fffffff
#define VUSECOUNT_GATE 0x80000000
/*
* Return the current usecount of a vnode.
*/
inline int
vrefcnt(struct vnode *vp)
{
return atomic_load_relaxed(&vp->v_usecount) & VUSECOUNT_MASK;
}
/* Vnode state operations and diagnostics. */
#if defined(DIAGNOSTIC)
#define VSTATE_VALID(state) \
((state) != VS_ACTIVE && (state) != VS_MARKER)
#define VSTATE_GET(vp) \
vstate_assert_get((vp), __func__, __LINE__)
#define VSTATE_CHANGE(vp, from, to) \
vstate_assert_change((vp), (from), (to), __func__, __LINE__)
#define VSTATE_WAIT_STABLE(vp) \
vstate_assert_wait_stable((vp), __func__, __LINE__)
void
_vstate_assert(vnode_t *vp, enum vnode_state state, const char *func, int line,
bool has_lock)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
int refcnt = vrefcnt(vp);
if (!has_lock) {
/*
* Prevent predictive loads from the CPU, but check the state
* without loooking first.
*/
membar_enter();
if (state == VS_ACTIVE && refcnt > 0 &&
(vip->vi_state == VS_LOADED || vip->vi_state == VS_BLOCKED))
return;
if (vip->vi_state == state)
return;
mutex_enter((vp)->v_interlock);
}
KASSERTMSG(mutex_owned(vp->v_interlock), "at %s:%d", func, line);
if ((state == VS_ACTIVE && refcnt > 0 &&
(vip->vi_state == VS_LOADED || vip->vi_state == VS_BLOCKED)) ||
vip->vi_state == state) {
if (!has_lock)
mutex_exit((vp)->v_interlock);
return;
}
vnpanic(vp, "state is %s, usecount %d, expected %s at %s:%d",
vstate_name(vip->vi_state), refcnt,
vstate_name(state), func, line);
}
static enum vnode_state
vstate_assert_get(vnode_t *vp, const char *func, int line)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
KASSERTMSG(mutex_owned(vp->v_interlock), "at %s:%d", func, line);
if (! VSTATE_VALID(vip->vi_state))
vnpanic(vp, "state is %s at %s:%d",
vstate_name(vip->vi_state), func, line);
return vip->vi_state;
}
static void
vstate_assert_wait_stable(vnode_t *vp, const char *func, int line)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
KASSERTMSG(mutex_owned(vp->v_interlock), "at %s:%d", func, line);
if (! VSTATE_VALID(vip->vi_state))
vnpanic(vp, "state is %s at %s:%d",
vstate_name(vip->vi_state), func, line);
while (vip->vi_state != VS_LOADED && vip->vi_state != VS_RECLAIMED)
cv_wait(&vp->v_cv, vp->v_interlock);
if (! VSTATE_VALID(vip->vi_state))
vnpanic(vp, "state is %s at %s:%d",
vstate_name(vip->vi_state), func, line);
}
static void
vstate_assert_change(vnode_t *vp, enum vnode_state from, enum vnode_state to,
const char *func, int line)
{
bool gated = (atomic_load_relaxed(&vp->v_usecount) & VUSECOUNT_GATE);
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
KASSERTMSG(mutex_owned(vp->v_interlock), "at %s:%d", func, line);
if (from == VS_LOADING)
KASSERTMSG(mutex_owned(&vcache_lock), "at %s:%d", func, line);
if (! VSTATE_VALID(from))
vnpanic(vp, "from is %s at %s:%d",
vstate_name(from), func, line);
if (! VSTATE_VALID(to))
vnpanic(vp, "to is %s at %s:%d",
vstate_name(to), func, line);
if (vip->vi_state != from)
vnpanic(vp, "from is %s, expected %s at %s:%d\n",
vstate_name(vip->vi_state), vstate_name(from), func, line);
if ((from == VS_LOADED) != gated)
vnpanic(vp, "state is %s, gate %d does not match at %s:%d\n",
vstate_name(vip->vi_state), gated, func, line);
/* Open/close the gate for vcache_tryvget(). */
if (to == VS_LOADED)
atomic_or_uint(&vp->v_usecount, VUSECOUNT_GATE);
else
atomic_and_uint(&vp->v_usecount, ~VUSECOUNT_GATE);
vip->vi_state = to;
if (from == VS_LOADING)
cv_broadcast(&vcache_cv);
if (to == VS_LOADED || to == VS_RECLAIMED)
cv_broadcast(&vp->v_cv);
}
#else /* defined(DIAGNOSTIC) */
#define VSTATE_GET(vp) \
(VNODE_TO_VIMPL((vp))->vi_state)
#define VSTATE_CHANGE(vp, from, to) \
vstate_change((vp), (from), (to))
#define VSTATE_WAIT_STABLE(vp) \
vstate_wait_stable((vp))
void
_vstate_assert(vnode_t *vp, enum vnode_state state, const char *func, int line,
bool has_lock)
{
}
static void
vstate_wait_stable(vnode_t *vp)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
while (vip->vi_state != VS_LOADED && vip->vi_state != VS_RECLAIMED)
cv_wait(&vp->v_cv, vp->v_interlock);
}
static void
vstate_change(vnode_t *vp, enum vnode_state from, enum vnode_state to)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
/* Open/close the gate for vcache_tryvget(). */
if (to == VS_LOADED)
atomic_or_uint(&vp->v_usecount, VUSECOUNT_GATE);
else
atomic_and_uint(&vp->v_usecount, ~VUSECOUNT_GATE);
vip->vi_state = to;
if (from == VS_LOADING)
cv_broadcast(&vcache_cv);
if (to == VS_LOADED || to == VS_RECLAIMED)
cv_broadcast(&vp->v_cv);
}
#endif /* defined(DIAGNOSTIC) */
void
vfs_vnode_sysinit(void)
{
int error __diagused, i;
dead_rootmount = vfs_mountalloc(&dead_vfsops, NULL);
KASSERT(dead_rootmount != NULL);
dead_rootmount->mnt_iflag |= IMNT_MPSAFE;
mutex_init(&vdrain_lock, MUTEX_DEFAULT, IPL_NONE);
for (i = 0; i < LRU_COUNT; i++) {
TAILQ_INIT(&lru_list[i]);
}
vcache_init();
cv_init(&vdrain_cv, "vdrain");
cv_init(&vdrain_gen_cv, "vdrainwt");
error = kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, vdrain_thread,
NULL, &vdrain_lwp, "vdrain");
KASSERTMSG((error == 0), "kthread_create(vdrain) failed: %d", error);
}
/*
* Allocate a new marker vnode.
*/
vnode_t *
vnalloc_marker(struct mount *mp)
{
vnode_impl_t *vip;
vnode_t *vp;
vip = pool_cache_get(vcache_pool, PR_WAITOK);
memset(vip, 0, sizeof(*vip));
vp = VIMPL_TO_VNODE(vip);
uvm_obj_init(&vp->v_uobj, &uvm_vnodeops, true, 1);
vp->v_mount = mp;
vp->v_type = VBAD;
vp->v_interlock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
vip->vi_state = VS_MARKER;
return vp;
}
/*
* Free a marker vnode.
*/
void
vnfree_marker(vnode_t *vp)
{
vnode_impl_t *vip;
vip = VNODE_TO_VIMPL(vp);
KASSERT(vip->vi_state == VS_MARKER);
mutex_obj_free(vp->v_interlock);
uvm_obj_destroy(&vp->v_uobj, true);
pool_cache_put(vcache_pool, vip);
}
/*
* Test a vnode for being a marker vnode.
*/
bool
vnis_marker(vnode_t *vp)
{
return (VNODE_TO_VIMPL(vp)->vi_state == VS_MARKER);
}
/*
* Return the lru list this node should be on.
*/
static vnodelst_t *
lru_which(vnode_t *vp)
{
KASSERT(mutex_owned(vp->v_interlock));
if (vp->v_holdcnt > 0)
return &lru_list[LRU_HOLD];
else
return &lru_list[LRU_FREE];
}
/*
* Put vnode to end of given list.
* Both the current and the new list may be NULL, used on vnode alloc/free.
* Adjust numvnodes and signal vdrain thread if there is work.
*/
static void
lru_requeue(vnode_t *vp, vnodelst_t *listhd)
{
vnode_impl_t *vip;
int d;
/*
* If the vnode is on the correct list, and was put there recently,
* then leave it be, thus avoiding huge cache and lock contention.
*/
vip = VNODE_TO_VIMPL(vp);
if (listhd == vip->vi_lrulisthd &&
(getticks() - vip->vi_lrulisttm) < hz) {
return;
}
mutex_enter(&vdrain_lock);
d = 0;
if (vip->vi_lrulisthd != NULL)
TAILQ_REMOVE(vip->vi_lrulisthd, vip, vi_lrulist);
else
d++;
vip->vi_lrulisthd = listhd;
vip->vi_lrulisttm = getticks();
if (vip->vi_lrulisthd != NULL)
TAILQ_INSERT_TAIL(vip->vi_lrulisthd, vip, vi_lrulist);
else
d--;
if (d != 0) {
/*
* Looks strange? This is not a bug. Don't store
* numvnodes unless there is a change - avoid false
* sharing on MP.
*/
numvnodes += d;
}
if ((d > 0 && numvnodes > desiredvnodes) ||
listhd == &lru_list[LRU_VRELE])
cv_signal(&vdrain_cv);
mutex_exit(&vdrain_lock);
}
/*
* Release deferred vrele vnodes for this mount.
* Called with file system suspended.
*/
void
vrele_flush(struct mount *mp)
{
vnode_impl_t *vip, *marker;
vnode_t *vp;
int when = 0;
KASSERT(fstrans_is_owner(mp));
marker = VNODE_TO_VIMPL(vnalloc_marker(NULL));
mutex_enter(&vdrain_lock);
TAILQ_INSERT_HEAD(&lru_list[LRU_VRELE], marker, vi_lrulist);
while ((vip = TAILQ_NEXT(marker, vi_lrulist))) {
TAILQ_REMOVE(&lru_list[LRU_VRELE], marker, vi_lrulist);
TAILQ_INSERT_AFTER(&lru_list[LRU_VRELE], vip, marker,
vi_lrulist);
vp = VIMPL_TO_VNODE(vip);
if (vnis_marker(vp))
continue;
KASSERT(vip->vi_lrulisthd == &lru_list[LRU_VRELE]);
TAILQ_REMOVE(vip->vi_lrulisthd, vip, vi_lrulist);
vip->vi_lrulisthd = &lru_list[LRU_HOLD];
vip->vi_lrulisttm = getticks();
TAILQ_INSERT_TAIL(vip->vi_lrulisthd, vip, vi_lrulist);
mutex_exit(&vdrain_lock);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
mutex_enter(vp->v_interlock);
vrelel(vp, 0, LK_EXCLUSIVE);
if (getticks() > when) {
yield();
when = getticks() + hz / 10;
}
mutex_enter(&vdrain_lock);
}
TAILQ_REMOVE(&lru_list[LRU_VRELE], marker, vi_lrulist);
mutex_exit(&vdrain_lock);
vnfree_marker(VIMPL_TO_VNODE(marker));
}
/*
* Reclaim a cached vnode. Used from vdrain_thread only.
*/
static __inline void
vdrain_remove(vnode_t *vp)
{
struct mount *mp;
KASSERT(mutex_owned(&vdrain_lock));
/* Probe usecount (unlocked). */
if (vrefcnt(vp) > 0)
return;
/* Try v_interlock -- we lock the wrong direction! */
if (!mutex_tryenter(vp->v_interlock))
return;
/* Probe usecount and state. */
if (vrefcnt(vp) > 0 || VSTATE_GET(vp) != VS_LOADED) {
mutex_exit(vp->v_interlock);
return;
}
mp = vp->v_mount;
if (fstrans_start_nowait(mp) != 0) {
mutex_exit(vp->v_interlock);
return;
}
vdrain_retry = true;
mutex_exit(&vdrain_lock);
if (vcache_vget(vp) == 0) {
if (!vrecycle(vp)) {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
mutex_enter(vp->v_interlock);
vrelel(vp, 0, LK_EXCLUSIVE);
}
}
fstrans_done(mp);
mutex_enter(&vdrain_lock);
}
/*
* Release a cached vnode. Used from vdrain_thread only.
*/
static __inline void
vdrain_vrele(vnode_t *vp)
{
vnode_impl_t *vip = VNODE_TO_VIMPL(vp);
struct mount *mp;
KASSERT(mutex_owned(&vdrain_lock));
mp = vp->v_mount;
if (fstrans_start_nowait(mp) != 0)
return;
/*
* First remove the vnode from the vrele list.
* Put it on the last lru list, the last vrele()
* will put it back onto the right list before
* its usecount reaches zero.
*/
KASSERT(vip->vi_lrulisthd == &lru_list[LRU_VRELE]);
TAILQ_REMOVE(vip->vi_lrulisthd, vip, vi_lrulist);
vip->vi_lrulisthd = &lru_list[LRU_HOLD];
vip->vi_lrulisttm = getticks();
TAILQ_INSERT_TAIL(vip->vi_lrulisthd, vip, vi_lrulist);
vdrain_retry = true;
mutex_exit(&vdrain_lock);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
mutex_enter(vp->v_interlock);
vrelel(vp, 0, LK_EXCLUSIVE);
fstrans_done(mp);
mutex_enter(&vdrain_lock);
}
/*
* Helper thread to keep the number of vnodes below desiredvnodes
* and release vnodes from asynchronous vrele.
*/
static void
vdrain_thread(void *cookie)
{
int i;
u_int target;
vnode_impl_t *vip, *marker;
marker = VNODE_TO_VIMPL(vnalloc_marker(NULL));
mutex_enter(&vdrain_lock);
for (;;) {
vdrain_retry = false;
target = desiredvnodes - desiredvnodes/10;
for (i = 0; i < LRU_COUNT; i++) {
TAILQ_INSERT_HEAD(&lru_list[i], marker, vi_lrulist);
while ((vip = TAILQ_NEXT(marker, vi_lrulist))) {
TAILQ_REMOVE(&lru_list[i], marker, vi_lrulist);
TAILQ_INSERT_AFTER(&lru_list[i], vip, marker,
vi_lrulist);
if (vnis_marker(VIMPL_TO_VNODE(vip)))
continue;
if (i == LRU_VRELE)
vdrain_vrele(VIMPL_TO_VNODE(vip));
else if (numvnodes < target)
break;
else
vdrain_remove(VIMPL_TO_VNODE(vip));
}
TAILQ_REMOVE(&lru_list[i], marker, vi_lrulist);
}
if (vdrain_retry) {
kpause("vdrainrt", false, 1, &vdrain_lock);
} else {
vdrain_gen++;
cv_broadcast(&vdrain_gen_cv);
cv_wait(&vdrain_cv, &vdrain_lock);
}
}
}
/*
* Try to drop reference on a vnode. Abort if we are releasing the
* last reference. Note: this _must_ succeed if not the last reference.
*/
static bool
vtryrele(vnode_t *vp)
{
u_int use, next;
for (use = atomic_load_relaxed(&vp->v_usecount);; use = next) {
if (__predict_false((use & VUSECOUNT_MASK) == 1)) {
return false;
}
KASSERT((use & VUSECOUNT_MASK) > 1);
next = atomic_cas_uint(&vp->v_usecount, use, use - 1);
if (__predict_true(next == use)) {
return true;
}
}
}
/*
* vput: unlock and release the reference.
*/
void
vput(vnode_t *vp)
{
int lktype;
/*
* Do an unlocked check of the usecount. If it looks like we're not
* about to drop the last reference, then unlock the vnode and try
* to drop the reference. If it ends up being the last reference
* after all, vrelel() can fix it all up. Most of the time this
* will all go to plan.
*/
if (vrefcnt(vp) > 1) {
VOP_UNLOCK(vp);
if (vtryrele(vp)) {
return;
}
lktype = LK_NONE;
} else if ((vp->v_vflag & VV_LOCKSWORK) == 0) {
VOP_UNLOCK(vp);
lktype = LK_NONE;
} else {
lktype = VOP_ISLOCKED(vp);
KASSERT(lktype != LK_NONE);
}
mutex_enter(vp->v_interlock);
vrelel(vp, 0, lktype);
}
/*
* Vnode release. If reference count drops to zero, call inactive
* routine and either return to freelist or free to the pool.
*/
static void
vrelel(vnode_t *vp, int flags, int lktype)
{
const bool async = ((flags & VRELEL_ASYNC) != 0);
bool recycle, defer;
int error;
KASSERT(mutex_owned(vp->v_interlock));
if (__predict_false(vp->v_op == dead_vnodeop_p &&
VSTATE_GET(vp) != VS_RECLAIMED)) {
vnpanic(vp, "dead but not clean");
}
/*
* If not the last reference, just drop the reference count and
* unlock. VOP_UNLOCK() is called here without a vnode reference
* held, but is ok as the hold of v_interlock will stop the vnode
* from disappearing.
*/
if (vtryrele(vp)) {
if (lktype != LK_NONE) {
VOP_UNLOCK(vp);
}
mutex_exit(vp->v_interlock);
return;
}
if (vrefcnt(vp) <= 0 || vp->v_writecount != 0) {
vnpanic(vp, "%s: bad ref count", __func__);
}
#ifdef DIAGNOSTIC
if ((vp->v_type == VBLK || vp->v_type == VCHR) &&
vp->v_specnode != NULL && vp->v_specnode->sn_opencnt != 0) {
vprint("vrelel: missing VOP_CLOSE()", vp);
}
#endif
/*
* First try to get the vnode locked for VOP_INACTIVE().
* Defer vnode release to vdrain_thread if caller requests
* it explicitly, is the pagedaemon or the lock failed.
*/
defer = false;
if ((curlwp == uvm.pagedaemon_lwp) || async) {
defer = true;
} else if (lktype == LK_SHARED) {
/* Excellent chance of getting, if the last ref. */
error = vn_lock(vp, LK_UPGRADE | LK_RETRY |
LK_NOWAIT);
if (error != 0) {
defer = true;
} else {
lktype = LK_EXCLUSIVE;
}
} else if (lktype == LK_NONE) {
/* Excellent chance of getting, if the last ref. */
error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY |
LK_NOWAIT);
if (error != 0) {
defer = true;
} else {
lktype = LK_EXCLUSIVE;
}
}
KASSERT(mutex_owned(vp->v_interlock));
if (defer) {
/*
* Defer reclaim to the kthread; it's not safe to
* clean it here. We donate it our last reference.
*/
if (lktype != LK_NONE) {
VOP_UNLOCK(vp);
}
lru_requeue(vp, &lru_list[LRU_VRELE]);
mutex_exit(vp->v_interlock);
return;
}
KASSERT(lktype == LK_EXCLUSIVE);
/*
* If not clean, deactivate the vnode, but preserve
* our reference across the call to VOP_INACTIVE().
*/
if (VSTATE_GET(vp) == VS_RECLAIMED) {
VOP_UNLOCK(vp);
} else {
/*
* If VOP_INACTIVE() indicates that the file has been
* deleted, then recycle the vnode.
*
* Note that VOP_INACTIVE() will not drop the vnode lock.
*/
mutex_exit(vp->v_interlock);
recycle = false;
VOP_INACTIVE(vp, &recycle);
rw_enter(vp->v_uobj.vmobjlock, RW_WRITER);
mutex_enter(vp->v_interlock);
for (;;) {
/*
* If no longer the last reference, try to shed it.
* On success, drop the interlock last thereby
* preventing the vnode being freed behind us.
*/
if (vtryrele(vp)) {
VOP_UNLOCK(vp);
rw_exit(vp->v_uobj.vmobjlock);
mutex_exit(vp->v_interlock);
return;
}
/*
* Block new references then check again to see if a
* new reference was acquired in the meantime. If
* it was, restore the vnode state and try again.
*/
if (recycle) {
VSTATE_CHANGE(vp, VS_LOADED, VS_BLOCKED);
if (vrefcnt(vp) != 1) {
VSTATE_CHANGE(vp, VS_BLOCKED,
VS_LOADED);
continue;
}
}
break;
}
/* Take care of space accounting. */
if ((vp->v_iflag & VI_EXECMAP) != 0) {
cpu_count(CPU_COUNT_EXECPAGES, -vp->v_uobj.uo_npages);
}
vp->v_iflag &= ~(VI_TEXT|VI_EXECMAP|VI_WRMAP);
vp->v_vflag &= ~VV_MAPPED;
rw_exit(vp->v_uobj.vmobjlock);
/*
* Recycle the vnode if the file is now unused (unlinked),
* otherwise just free it.
*/
if (recycle) {
VSTATE_ASSERT(vp, VS_BLOCKED);
/* vcache_reclaim drops the lock. */
vcache_reclaim(vp);
} else {
VOP_UNLOCK(vp);
}
KASSERT(vrefcnt(vp) > 0);
}
if ((atomic_dec_uint_nv(&vp->v_usecount) & VUSECOUNT_MASK) != 0) {
/* Gained another reference while being reclaimed. */
mutex_exit(vp->v_interlock);
return;
}
if (VSTATE_GET(vp) == VS_RECLAIMED && vp->v_holdcnt == 0) {
/*
* It's clean so destroy it. It isn't referenced
* anywhere since it has been reclaimed.
*/
vcache_free(VNODE_TO_VIMPL(vp));
} else {
/*
* Otherwise, put it back onto the freelist. It
* can't be destroyed while still associated with
* a file system.
*/
lru_requeue(vp, lru_which(vp));
mutex_exit(vp->v_interlock);
}
}
void
vrele(vnode_t *vp)
{
if (vtryrele(vp)) {
return;
}
mutex_enter(vp->v_interlock);
vrelel(vp, 0, LK_NONE);
}
/*
* Asynchronous vnode release, vnode is released in different context.
*/
void
vrele_async(vnode_t *vp)
{
if (vtryrele(vp)) {
return;
}
mutex_enter(vp->v_interlock);
vrelel(vp, VRELEL_ASYNC, LK_NONE);
}
/*
* Vnode reference, where a reference is already held by some other
* object (for example, a file structure).
*
* NB: lockless code sequences may rely on this not blocking.
*/
void
vref(vnode_t *vp)
{
KASSERT(vrefcnt(vp) > 0);
atomic_inc_uint(&vp->v_usecount);
}
/*
* Page or buffer structure gets a reference.
* Called with v_interlock held.
*/
void
vholdl(vnode_t *vp)
{
KASSERT(mutex_owned(vp->v_interlock));
if (vp->v_holdcnt++ == 0 && vrefcnt(vp) == 0)
lru_requeue(vp, lru_which(vp));
}
/*
* Page or buffer structure gets a reference.