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/* $OpenBSD: nfs_kq.c,v 1.27 2019/12/31 13:48:32 visa Exp $ */
/* $NetBSD: nfs_kq.c,v 1.7 2003/10/30 01:43:10 simonb Exp $ */
/*-
* Copyright (c) 2002 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/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/unistd.h>
#include <sys/file.h>
#include <sys/kthread.h>
#include <sys/rwlock.h>
#include <sys/queue.h>
#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_var.h>
void nfs_kqpoll(void *);
void filt_nfsdetach(struct knote *);
int filt_nfsread(struct knote *, long);
int filt_nfsvnode(struct knote *, long);
struct kevq {
SLIST_ENTRY(kevq) kev_link;
struct vnode *vp;
u_int usecount;
u_int flags;
#define KEVQ_BUSY 0x01 /* currently being processed */
#define KEVQ_WANT 0x02 /* want to change this entry */
struct timespec omtime; /* old modification time */
struct timespec octime; /* old change time */
nlink_t onlink; /* old number of references to file */
};
SLIST_HEAD(kevqlist, kevq);
struct rwlock nfskevq_lock = RWLOCK_INITIALIZER("nfskqlk");
struct proc *pnfskq;
struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist);
/*
* 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 */
void
nfs_kqpoll(void *arg)
{
struct kevq *ke;
struct vattr attr;
struct proc *p = pnfskq;
u_quad_t osize;
int error;
for(;;) {
rw_enter_write(&nfskevq_lock);
SLIST_FOREACH(ke, &kevlist, kev_link) {
struct nfsnode *np = VTONFS(ke->vp);
#ifdef DEBUG
printf("nfs_kqpoll on: ");
VOP_PRINT(ke->vp);
#endif
/* 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;
rw_exit_write(&nfskevq_lock);
/* save v_size, nfs_getattr() updates it */
osize = np->n_size;
error = VOP_GETATTR(ke->vp, &attr, p->p_ucred, p);
if (error == ESTALE) {
NFS_INVALIDATE_ATTRCACHE(np);
VN_KNOTE(ke->vp, NOTE_DELETE);
goto next;
}
/* following is a bit fragile, but about best
* we can get */
if (attr.va_size != osize) {
int flags = NOTE_WRITE;
if (attr.va_size > osize)
flags |= NOTE_EXTEND;
else
flags |= NOTE_TRUNCATE;
VN_KNOTE(ke->vp, flags);
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;
}
next:
rw_enter_write(&nfskevq_lock);
ke->flags &= ~KEVQ_BUSY;
if (ke->flags & KEVQ_WANT) {
ke->flags &= ~KEVQ_WANT;
wakeup(ke);
}
}
if (SLIST_EMPTY(&kevlist)) {
/* Nothing more to watch, exit */
pnfskq = NULL;
rw_exit_write(&nfskevq_lock);
kthread_exit(0);
}
rw_exit_write(&nfskevq_lock);
/* wait a while before checking for changes again */
tsleep(pnfskq, PSOCK, "nfskqpw", NFS_MINATTRTIMO * hz / 2);
}
}
void
filt_nfsdetach(struct knote *kn)
{
struct vnode *vp = (struct vnode *)kn->kn_hook;
struct kevq *ke;
SLIST_REMOVE(&vp->v_selectinfo.si_note, kn, knote, kn_selnext);
/* Remove the vnode from watch list */
rw_enter_write(&nfskevq_lock);
SLIST_FOREACH(ke, &kevlist, kev_link) {
if (ke->vp == vp) {
while (ke->flags & KEVQ_BUSY) {
ke->flags |= KEVQ_WANT;
rw_exit_write(&nfskevq_lock);
tsleep_nsec(ke, PSOCK, "nfskqdet", INFSLP);
rw_enter_write(&nfskevq_lock);
}
if (ke->usecount > 1) {
/* keep, other kevents need this */
ke->usecount--;
} else {
/* last user, g/c */
SLIST_REMOVE(&kevlist, ke, kevq, kev_link);
free(ke, M_KEVENT, sizeof(*ke));
}
break;
}
}
rw_exit_write(&nfskevq_lock);
}
int
filt_nfsread(struct knote *kn, long hint)
{
struct vnode *vp = (struct vnode *)kn->kn_hook;
struct nfsnode *np = VTONFS(vp);
/*
* filesystem is gone, so set the EOF flag and schedule
* the knote for deletion.
*/
if (hint == NOTE_REVOKE) {
kn->kn_flags |= (EV_EOF | EV_ONESHOT);
return (1);
}
kn->kn_data = np->n_size - foffset(kn->kn_fp);
#ifdef DEBUG
printf("nfsread event. %lld\n", kn->kn_data);
#endif
if (kn->kn_data == 0 && kn->kn_sfflags & NOTE_EOF) {
kn->kn_fflags |= NOTE_EOF;
return (1);
}
return (kn->kn_data != 0);
}
int
filt_nfsvnode(struct knote *kn, long hint)
{
if (kn->kn_sfflags & hint)
kn->kn_fflags |= hint;
if (hint == NOTE_REVOKE) {
kn->kn_flags |= EV_EOF;
return (1);
}
return (kn->kn_fflags != 0);
}
static const struct filterops nfsread_filtops = {
.f_isfd = 1,
.f_attach = NULL,
.f_detach = filt_nfsdetach,
.f_event = filt_nfsread,
};
static const struct filterops nfsvnode_filtops = {
.f_isfd = 1,
.f_attach = NULL,
.f_detach = filt_nfsdetach,
.f_event = filt_nfsvnode,
};
int
nfs_kqfilter(void *v)
{
struct vop_kqfilter_args *ap = v;
struct vnode *vp;
struct knote *kn;
struct kevq *ke;
int error = 0;
struct vattr attr;
struct proc *p = curproc; /* XXX */
vp = ap->a_vp;
kn = ap->a_kn;
#ifdef DEBUG
printf("nfs_kqfilter(%d) on: ", kn->kn_filter);
VOP_PRINT(vp);
#endif
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);
}
kn->kn_hook = vp;
/*
* 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));
(void) VOP_GETATTR(vp, &attr, p->p_ucred, p);
rw_enter_write(&nfskevq_lock);
/* ensure the poller is running */
if (!pnfskq) {
error = kthread_create(nfs_kqpoll, NULL, &pnfskq,
"nfskqpoll");
if (error)
goto out;
}
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 = malloc(sizeof(*ke), M_KEVENT, M_WAITOK);
ke->vp = vp;
ke->usecount = 1;
ke->flags = 0;
ke->omtime = attr.va_mtime;
ke->octime = attr.va_ctime;
ke->onlink = attr.va_nlink;
SLIST_INSERT_HEAD(&kevlist, ke, kev_link);
}
/* kick the poller */
wakeup(pnfskq);
SLIST_INSERT_HEAD(&vp->v_selectinfo.si_note, kn, kn_selnext);
out:
rw_exit_write(&nfskevq_lock);
return (error);
}
|