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vfs_vnode.c
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vfs_vnode.c
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/* $NetBSD: vfs_vnode.c,v 1.153 2023/11/27 16:13:59 hannken 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 1.153 2023/11/27 16:13:59 hannken 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/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/threadpool.h>
#include <sys/vnode_impl.h>
#include <sys/wapbl.h>
#include <sys/fstrans.h>
#include <miscfs/deadfs/deadfs.h>
#include <miscfs/specfs/specdev.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).
*/
typedef struct {
vnode_impl_t *li_marker;
} lru_iter_t;
u_int numvnodes __cacheline_aligned;
static vnodelst_t lru_list[LRU_COUNT] __cacheline_aligned;
static struct threadpool *threadpool;
static struct threadpool_job vdrain_job;
static struct threadpool_job vrele_job;
static kmutex_t vdrain_lock __cacheline_aligned;
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 * lru_iter_first(int, lru_iter_t *);
static vnode_impl_t * lru_iter_next(lru_iter_t *);
static void lru_iter_release(lru_iter_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 vrele_deferred(vnode_impl_t *);
static void vrelel(vnode_t *, int, int);
static void vnpanic(vnode_t *, const char *, ...)
__printflike(2, 3);
static bool vdrain_one(u_int);
static void vdrain_task(struct threadpool_job *);
static void vrele_task(struct threadpool_job *);
/* Routines having to do with the management of the vnode table. */
/*
* The high bit of v_usecount is a gate for vcache_tryvget(). It's set
* only when the vnode state is LOADED.
* The next bit of v_usecount is a flag for vrelel(). It's set
* from vcache_vget() and vcache_tryvget() whenever the operation succeeds.
*/
#define VUSECOUNT_MASK 0x3fffffff
#define VUSECOUNT_GATE 0x80000000
#define VUSECOUNT_VGET 0x40000000
/*
* 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) {
enum vnode_state vstate = atomic_load_relaxed(&vip->vi_state);
if (state == VS_ACTIVE && refcnt > 0 &&
(vstate == VS_LOADED || vstate == VS_BLOCKED))
return;
if (vstate == 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) {
membar_release();
atomic_or_uint(&vp->v_usecount, VUSECOUNT_GATE);
} else {
atomic_and_uint(&vp->v_usecount, ~VUSECOUNT_GATE);
}
atomic_store_relaxed(&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) {
membar_release();
atomic_or_uint(&vp->v_usecount, VUSECOUNT_GATE);
} else {
atomic_and_uint(&vp->v_usecount, ~VUSECOUNT_GATE);
}
atomic_store_relaxed(&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();
error = threadpool_get(&threadpool, PRI_NONE);
KASSERTMSG((error == 0), "threadpool_get failed: %d", error);
threadpool_job_init(&vdrain_job, vdrain_task, &vdrain_lock, "vdrain");
threadpool_job_init(&vrele_job, vrele_task, &vdrain_lock, "vrele");
}
/*
* 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);
klist_init(&vip->vi_klist.vk_klist);
vp->v_klist = &vip->vi_klist;
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);
klist_fini(&vip->vi_klist.vk_klist);
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 (listhd == &lru_list[LRU_VRELE])
threadpool_schedule_job(threadpool, &vrele_job);
if (d > 0 && numvnodes > desiredvnodes)
threadpool_schedule_job(threadpool, &vdrain_job);
if (d > 0 && numvnodes > desiredvnodes + desiredvnodes / 16)
kpause("vnfull", false, MAX(1, mstohz(10)), &vdrain_lock);
mutex_exit(&vdrain_lock);
}
/*
* LRU list iterator.
* Caller holds vdrain_lock.
*/
static vnode_impl_t *
lru_iter_first(int idx, lru_iter_t *iterp)
{
vnode_impl_t *marker;
KASSERT(mutex_owned(&vdrain_lock));
mutex_exit(&vdrain_lock);
marker = VNODE_TO_VIMPL(vnalloc_marker(NULL));
mutex_enter(&vdrain_lock);
marker->vi_lrulisthd = &lru_list[idx];
iterp->li_marker = marker;
TAILQ_INSERT_HEAD(marker->vi_lrulisthd, marker, vi_lrulist);
return lru_iter_next(iterp);
}
static vnode_impl_t *
lru_iter_next(lru_iter_t *iter)
{
vnode_impl_t *vip, *marker;
vnodelst_t *listhd;
KASSERT(mutex_owned(&vdrain_lock));
marker = iter->li_marker;
listhd = marker->vi_lrulisthd;
while ((vip = TAILQ_NEXT(marker, vi_lrulist))) {
TAILQ_REMOVE(listhd, marker, vi_lrulist);
TAILQ_INSERT_AFTER(listhd, vip, marker, vi_lrulist);
if (!vnis_marker(VIMPL_TO_VNODE(vip)))
break;
}
return vip;
}
static void
lru_iter_release(lru_iter_t *iter)
{
vnode_impl_t *marker;
KASSERT(mutex_owned(&vdrain_lock));
marker = iter->li_marker;
TAILQ_REMOVE(marker->vi_lrulisthd, marker, vi_lrulist);
mutex_exit(&vdrain_lock);
vnfree_marker(VIMPL_TO_VNODE(marker));
mutex_enter(&vdrain_lock);
}
/*
* Release deferred vrele vnodes for this mount.
* Called with file system suspended.
*/
void
vrele_flush(struct mount *mp)
{
lru_iter_t iter;
vnode_impl_t *vip;
KASSERT(fstrans_is_owner(mp));
mutex_enter(&vdrain_lock);
for (vip = lru_iter_first(LRU_VRELE, &iter); vip != NULL;
vip = lru_iter_next(&iter)) {
if (VIMPL_TO_VNODE(vip)->v_mount != mp)
continue;
vrele_deferred(vip);
}
lru_iter_release(&iter);
mutex_exit(&vdrain_lock);
}
/*
* One pass through the LRU lists to keep the number of allocated
* vnodes below target. Returns true if target met.
*/
static bool
vdrain_one(u_int target)
{
int ix, lists[] = { LRU_FREE, LRU_HOLD };
lru_iter_t iter;
vnode_impl_t *vip;
vnode_t *vp;
struct mount *mp;
KASSERT(mutex_owned(&vdrain_lock));
for (ix = 0; ix < __arraycount(lists); ix++) {
for (vip = lru_iter_first(lists[ix], &iter); vip != NULL;
vip = lru_iter_next(&iter)) {
if (numvnodes < target) {
lru_iter_release(&iter);
return true;
}
vp = VIMPL_TO_VNODE(vip);
/* Probe usecount (unlocked). */
if (vrefcnt(vp) > 0)
continue;
/* Try v_interlock -- we lock the wrong direction! */
if (!mutex_tryenter(vp->v_interlock))
continue;
/* Probe usecount and state. */
if (vrefcnt(vp) > 0 || VSTATE_GET(vp) != VS_LOADED) {
mutex_exit(vp->v_interlock);
continue;
}
mutex_exit(&vdrain_lock);
mp = vp->v_mount;
if (fstrans_start_nowait(mp) != 0) {
mutex_exit(vp->v_interlock);
mutex_enter(&vdrain_lock);
continue;
}
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);
}
lru_iter_release(&iter);
}
return false;
}
/*
* threadpool task to keep the number of vnodes below desiredvnodes.
*/
static void
vdrain_task(struct threadpool_job *job)
{
u_int target;
target = desiredvnodes - desiredvnodes / 16;
mutex_enter(&vdrain_lock);
while (!vdrain_one(target))
kpause("vdrain", false, 1, &vdrain_lock);
threadpool_job_done(job);
mutex_exit(&vdrain_lock);
}
/*
* threadpool task to process asynchronous vrele.
*/
static void
vrele_task(struct threadpool_job *job)
{
int skipped;
lru_iter_t iter;
vnode_impl_t *vip;
struct mount *mp;
mutex_enter(&vdrain_lock);
while ((vip = lru_iter_first(LRU_VRELE, &iter)) != NULL) {
for (skipped = 0; vip != NULL; vip = lru_iter_next(&iter)) {
mp = VIMPL_TO_VNODE(vip)->v_mount;
if (fstrans_start_nowait(mp) == 0) {
vrele_deferred(vip);
fstrans_done(mp);
} else {
skipped++;
}
}
lru_iter_release(&iter);
if (skipped)
kpause("vrele", false, MAX(1, mstohz(10)), &vdrain_lock);
}
threadpool_job_done(job);
lru_iter_release(&iter);
mutex_exit(&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;
membar_release();
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 {
lktype = VOP_ISLOCKED(vp);
KASSERT(lktype != LK_NONE);
}
mutex_enter(vp->v_interlock);
vrelel(vp, 0, lktype);
}
/*
* Release a vnode from the deferred list.
*/
static void
vrele_deferred(vnode_impl_t *vip)
{
vnode_t *vp;
KASSERT(mutex_owned(&vdrain_lock));
KASSERT(vip->vi_lrulisthd == &lru_list[LRU_VRELE]);
vp = VIMPL_TO_VNODE(vip);
/*
* 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.
*/
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);
mutex_enter(&vdrain_lock);
}
/*
* 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, objlock_held;
u_int use, next;
int error;
objlock_held = false;
retry:
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 unlock and drop the reference count.
*
* Otherwise make sure we pass a point in time where we hold the
* last reference with VGET flag unset.
*/
for (use = atomic_load_relaxed(&vp->v_usecount);; use = next) {
if (__predict_false((use & VUSECOUNT_MASK) > 1)) {
if (objlock_held) {
objlock_held = false;
rw_exit(vp->v_uobj.vmobjlock);
}
if (lktype != LK_NONE) {
mutex_exit(vp->v_interlock);
lktype = LK_NONE;
VOP_UNLOCK(vp);
mutex_enter(vp->v_interlock);
}
if (vtryrele(vp)) {
mutex_exit(vp->v_interlock);
return;
}
next = atomic_load_relaxed(&vp->v_usecount);
continue;
}
KASSERT((use & VUSECOUNT_MASK) == 1);
next = use & ~VUSECOUNT_VGET;
if (next != use) {
next = atomic_cas_uint(&vp->v_usecount, use, next);
}
if (__predict_true(next == use)) {
break;
}
}
membar_acquire();
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
/*
* If already clean there is no need to lock, defer or
* deactivate this node.
*/
if (VSTATE_GET(vp) == VS_RECLAIMED) {
if (objlock_held) {
objlock_held = false;
rw_exit(vp->v_uobj.vmobjlock);
}
if (lktype != LK_NONE) {
mutex_exit(vp->v_interlock);
lktype = LK_NONE;
VOP_UNLOCK(vp);
mutex_enter(vp->v_interlock);
}
goto out;
}
/*
* First try to get the vnode locked for VOP_INACTIVE().
* Defer vnode release to vrele task 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 vrele task; it's not safe to
* clean it here. We donate it our last reference.
*/
if (lktype != LK_NONE) {
mutex_exit(vp->v_interlock);
VOP_UNLOCK(vp);
mutex_enter(vp->v_interlock);
}
lru_requeue(vp, &lru_list[LRU_VRELE]);
mutex_exit(vp->v_interlock);
return;
}
KASSERT(lktype == LK_EXCLUSIVE);
/* If the node gained another reference, retry. */
use = atomic_load_relaxed(&vp->v_usecount);
if ((use & VUSECOUNT_VGET) != 0) {
goto retry;
}
KASSERT((use & VUSECOUNT_MASK) == 1);
if ((vp->v_iflag & (VI_TEXT|VI_EXECMAP|VI_WRMAP)) != 0 ||
(vp->v_vflag & VV_MAPPED) != 0) {
/* Take care of space accounting. */
if (!objlock_held) {
objlock_held = true;
if (!rw_tryenter(vp->v_uobj.vmobjlock, RW_WRITER)) {
mutex_exit(vp->v_interlock);
rw_enter(vp->v_uobj.vmobjlock, RW_WRITER);
mutex_enter(vp->v_interlock);
goto retry;
}
}
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;
}
if (objlock_held) {
objlock_held = false;
rw_exit(vp->v_uobj.vmobjlock);
}
/*
* Deactivate the vnode, but preserve our reference across
* the call to VOP_INACTIVE().
*
* If VOP_INACTIVE() indicates that the file has been
* deleted, then recycle the vnode.
*
* Note that VOP_INACTIVE() will not drop the vnode lock.