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/* $NetBSD: nfs_kq.c,v 1.25 2011/10/24 11:43:30 hannken Exp $ */
/*-
* Copyright (c) 2002, 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jaromir Dolecek.
*
* 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.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: nfs_kq.c,v 1.25 2011/10/24 11:43:30 hannken Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/condvar.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/kmem.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/vnode.h>
#include <sys/unistd.h>
#include <sys/file.h>
#include <sys/kthread.h>
#include <uvm/uvm_extern.h>
#include <uvm/uvm.h>
#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_var.h>
struct kevq {
SLIST_ENTRY(kevq) kev_link;
struct vnode *vp;
u_int usecount;
u_int flags;
#define KEVQ_BUSY 0x01 /* currently being processed */
struct timespec omtime; /* old modification time */
struct timespec octime; /* old change time */
nlink_t onlink; /* old number of references to file */
kcondvar_t cv;
};
SLIST_HEAD(kevqlist, kevq);
static kmutex_t nfskq_lock;
static struct lwp *nfskq_thread;
static kcondvar_t nfskq_cv;
static struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist);
static bool nfskq_thread_exit;
void
nfs_kqinit(void)
{
mutex_init(&nfskq_lock, MUTEX_DEFAULT, IPL_NONE);
cv_init(&nfskq_cv, "nfskqpw");
}
void
nfs_kqfini(void)
{
if (nfskq_thread != NULL) {
mutex_enter(&nfskq_lock);
nfskq_thread_exit = true;
cv_broadcast(&nfskq_cv);
do {
cv_wait(&nfskq_cv, &nfskq_lock);
} while (nfskq_thread != NULL);
mutex_exit(&nfskq_lock);
}
mutex_destroy(&nfskq_lock);
cv_destroy(&nfskq_cv);
}
/*
* This quite simplistic routine periodically checks for server changes
* of any of the watched files every NFS_MINATTRTIMO/2 seconds.
* Only changes in size, modification time, change time and nlinks
* are being checked, everything else is ignored.
* The routine only calls VOP_GETATTR() when it's likely it would get
* some new data, i.e. when the vnode expires from attrcache. This
* should give same result as periodically running stat(2) from userland,
* while keeping CPU/network usage low, and still provide proper kevent
* semantics.
* The poller thread is created when first vnode is added to watch list,
* and exits when the watch list is empty. The overhead of thread creation
* isn't really important, neither speed of attach and detach of knote.
*/
/* ARGSUSED */
static void
nfs_kqpoll(void *arg)
{
struct kevq *ke;
struct vattr attr;
struct lwp *l = curlwp;
u_quad_t osize;
mutex_enter(&nfskq_lock);
while (!nfskq_thread_exit) {
SLIST_FOREACH(ke, &kevlist, kev_link) {
/* skip if still in attrcache */
if (nfs_getattrcache(ke->vp, &attr) != ENOENT)
continue;
/*
* Mark entry busy, release lock and check
* for changes.
*/
ke->flags |= KEVQ_BUSY;
mutex_exit(&nfskq_lock);
/* save v_size, nfs_getattr() updates it */
osize = ke->vp->v_size;
memset(&attr, 0, sizeof(attr));
vn_lock(ke->vp, LK_SHARED | LK_RETRY);
(void) VOP_GETATTR(ke->vp, &attr, l->l_cred);
VOP_UNLOCK(ke->vp);
/* following is a bit fragile, but about best
* we can get */
if (attr.va_size != osize) {
int extended = (attr.va_size > osize);
VN_KNOTE(ke->vp, NOTE_WRITE
| (extended ? NOTE_EXTEND : 0));
ke->omtime = attr.va_mtime;
} else if (attr.va_mtime.tv_sec != ke->omtime.tv_sec
|| attr.va_mtime.tv_nsec != ke->omtime.tv_nsec) {
VN_KNOTE(ke->vp, NOTE_WRITE);
ke->omtime = attr.va_mtime;
}
if (attr.va_ctime.tv_sec != ke->octime.tv_sec
|| attr.va_ctime.tv_nsec != ke->octime.tv_nsec) {
VN_KNOTE(ke->vp, NOTE_ATTRIB);
ke->octime = attr.va_ctime;
}
if (attr.va_nlink != ke->onlink) {
VN_KNOTE(ke->vp, NOTE_LINK);
ke->onlink = attr.va_nlink;
}
mutex_enter(&nfskq_lock);
ke->flags &= ~KEVQ_BUSY;
cv_signal(&ke->cv);
}
if (SLIST_EMPTY(&kevlist)) {
/* Nothing more to watch, exit */
nfskq_thread = NULL;
mutex_exit(&nfskq_lock);
kthread_exit(0);
}
/* wait a while before checking for changes again */
cv_timedwait(&nfskq_cv, &nfskq_lock,
NFS_MINATTRTIMO * hz / 2);
}
nfskq_thread = NULL;
cv_broadcast(&nfskq_cv);
mutex_exit(&nfskq_lock);
}
static void
filt_nfsdetach(struct knote *kn)
{
struct vnode *vp = (struct vnode *)kn->kn_hook;
struct kevq *ke;
mutex_enter(vp->v_interlock);
SLIST_REMOVE(&vp->v_klist, kn, knote, kn_selnext);
mutex_exit(vp->v_interlock);
/* Remove the vnode from watch list */
mutex_enter(&nfskq_lock);
SLIST_FOREACH(ke, &kevlist, kev_link) {
if (ke->vp == vp) {
while (ke->flags & KEVQ_BUSY) {
cv_wait(&ke->cv, &nfskq_lock);
}
if (ke->usecount > 1) {
/* keep, other kevents need this */
ke->usecount--;
} else {
/* last user, g/c */
cv_destroy(&ke->cv);
SLIST_REMOVE(&kevlist, ke, kevq, kev_link);
kmem_free(ke, sizeof(*ke));
}
break;
}
}
mutex_exit(&nfskq_lock);
}
static int
filt_nfsread(struct knote *kn, long hint)
{
struct vnode *vp = (struct vnode *)kn->kn_hook;
int rv;
/*
* filesystem is gone, so set the EOF flag and schedule
* the knote for deletion.
*/
switch (hint) {
case NOTE_REVOKE:
KASSERT(mutex_owned(vp->v_interlock));
kn->kn_flags |= (EV_EOF | EV_ONESHOT);
return (1);
case 0:
mutex_enter(vp->v_interlock);
kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset;
rv = (kn->kn_data != 0);
mutex_exit(vp->v_interlock);
return rv;
default:
KASSERT(mutex_owned(vp->v_interlock));
kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset;
return (kn->kn_data != 0);
}
}
static int
filt_nfsvnode(struct knote *kn, long hint)
{
struct vnode *vp = (struct vnode *)kn->kn_hook;
int fflags;
switch (hint) {
case NOTE_REVOKE:
KASSERT(mutex_owned(vp->v_interlock));
kn->kn_flags |= EV_EOF;
if ((kn->kn_sfflags & hint) != 0)
kn->kn_fflags |= hint;
return (1);
case 0:
mutex_enter(vp->v_interlock);
fflags = kn->kn_fflags;
mutex_exit(vp->v_interlock);
break;
default:
KASSERT(mutex_owned(vp->v_interlock));
if ((kn->kn_sfflags & hint) != 0)
kn->kn_fflags |= hint;
fflags = kn->kn_fflags;
break;
}
return (fflags != 0);
}
static const struct filterops nfsread_filtops =
{ 1, NULL, filt_nfsdetach, filt_nfsread };
static const struct filterops nfsvnode_filtops =
{ 1, NULL, filt_nfsdetach, filt_nfsvnode };
int
nfs_kqfilter(void *v)
{
struct vop_kqfilter_args /* {
struct vnode *a_vp;
struct knote *a_kn;
} */ *ap = v;
struct vnode *vp;
struct knote *kn;
struct kevq *ke;
int error = 0;
struct vattr attr;
struct lwp *l = curlwp;
vp = ap->a_vp;
kn = ap->a_kn;
switch (kn->kn_filter) {
case EVFILT_READ:
kn->kn_fop = &nfsread_filtops;
break;
case EVFILT_VNODE:
kn->kn_fop = &nfsvnode_filtops;
break;
default:
return (EINVAL);
}
/*
* Put the vnode to watched list.
*/
/*
* Fetch current attributes. It's only needed when the vnode
* is not watched yet, but we need to do this without lock
* held. This is likely cheap due to attrcache, so do it now.
*/
memset(&attr, 0, sizeof(attr));
vn_lock(vp, LK_SHARED | LK_RETRY);
(void) VOP_GETATTR(vp, &attr, l->l_cred);
VOP_UNLOCK(vp);
mutex_enter(&nfskq_lock);
/* ensure the poller is running */
if (!nfskq_thread) {
error = kthread_create(PRI_NONE, 0, NULL, nfs_kqpoll,
NULL, &nfskq_thread, "nfskqpoll");
if (error) {
mutex_exit(&nfskq_lock);
return error;
}
}
SLIST_FOREACH(ke, &kevlist, kev_link) {
if (ke->vp == vp)
break;
}
if (ke) {
/* already watched, so just bump usecount */
ke->usecount++;
} else {
/* need a new one */
ke = kmem_alloc(sizeof(*ke), KM_SLEEP);
ke->vp = vp;
ke->usecount = 1;
ke->flags = 0;
ke->omtime = attr.va_mtime;
ke->octime = attr.va_ctime;
ke->onlink = attr.va_nlink;
cv_init(&ke->cv, "nfskqdet");
SLIST_INSERT_HEAD(&kevlist, ke, kev_link);
}
mutex_enter(vp->v_interlock);
SLIST_INSERT_HEAD(&vp->v_klist, kn, kn_selnext);
kn->kn_hook = vp;
mutex_exit(vp->v_interlock);
/* kick the poller */
cv_signal(&nfskq_cv);
mutex_exit(&nfskq_lock);
return (error);
}
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