nfs_kq.c revision 1.7 
1/*	$NetBSD: nfs_kq.c,v 1.7 2003/10/30 01:43:10 simonb Exp $	*/
2
3/*-
4 * Copyright (c) 2002 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jaromir Dolecek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *        This product includes software developed by the NetBSD
21 *        Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 *    contributors may be used to endorse or promote products derived
24 *    from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include <sys/cdefs.h>
40__KERNEL_RCSID(0, "$NetBSD: nfs_kq.c,v 1.7 2003/10/30 01:43:10 simonb Exp $");
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/kernel.h>
45#include <sys/proc.h>
46#include <sys/mount.h>
47#include <sys/malloc.h>
48#include <sys/vnode.h>
49#include <sys/unistd.h>
50#include <sys/file.h>
51#include <sys/kthread.h>
52
53#include <uvm/uvm_extern.h>
54#include <uvm/uvm.h>
55
56#include <nfs/rpcv2.h>
57#include <nfs/nfsproto.h>
58#include <nfs/nfs.h>
59#include <nfs/nfsnode.h>
60#include <nfs/nfs_var.h>
61
62struct kevq {
63	SLIST_ENTRY(kevq)	kev_link;
64	struct vnode		*vp;
65	u_int			usecount;
66	u_int			flags;
67#define KEVQ_BUSY	0x01	/* currently being processed */
68#define KEVQ_WANT	0x02	/* want to change this entry */
69	struct timespec		omtime;	/* old modification time */
70	struct timespec		octime;	/* old change time */
71	nlink_t			onlink;	/* old number of references to file */
72};
73SLIST_HEAD(kevqlist, kevq);
74
75static struct lock nfskevq_lock;
76static struct proc *pnfskq;
77static struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist);
78
79void
80nfs_kqinit(void)
81{
82	lockinit(&nfskevq_lock, PSOCK, "nfskqlck", 0, 0);
83}
84
85/*
86 * This quite simplistic routine periodically checks for server changes
87 * of any of the watched files every NFS_MINATTRTIMO/2 seconds.
88 * Only changes in size, modification time, change time and nlinks
89 * are being checked, everything else is ignored.
90 * The routine only calls VOP_GETATTR() when it's likely it would get
91 * some new data, i.e. when the vnode expires from attrcache. This
92 * should give same result as periodically running stat(2) from userland,
93 * while keeping CPU/network usage low, and still provide proper kevent
94 * semantics.
95 * The poller thread is created when first vnode is added to watch list,
96 * and exits when the watch list is empty. The overhead of thread creation
97 * isn't really important, neither speed of attach and detach of knote.
98 */
99/* ARGSUSED */
100static void
101nfs_kqpoll(void *arg)
102{
103	struct kevq *ke;
104	struct vattr attr;
105	struct proc *p = pnfskq;
106	u_quad_t osize;
107
108	for(;;) {
109		lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL);
110		SLIST_FOREACH(ke, &kevlist, kev_link) {
111			/* skip if still in attrcache */
112			if (nfs_getattrcache(ke->vp, &attr) != ENOENT)
113				continue;
114
115			/*
116			 * Mark entry busy, release lock and check
117			 * for changes.
118			 */
119			ke->flags |= KEVQ_BUSY;
120			lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
121
122			/* save v_size, nfs_getattr() updates it */
123			osize = ke->vp->v_size;
124
125			(void) VOP_GETATTR(ke->vp, &attr, p->p_ucred, p);
126
127			/* following is a bit fragile, but about best
128			 * we can get */
129			if (attr.va_size != osize) {
130				int extended = (attr.va_size > osize);
131				VN_KNOTE(ke->vp, NOTE_WRITE
132					| (extended ? NOTE_EXTEND : 0));
133				ke->omtime = attr.va_mtime;
134			} else if (attr.va_mtime.tv_sec != ke->omtime.tv_sec
135			    || attr.va_mtime.tv_nsec != ke->omtime.tv_nsec) {
136				VN_KNOTE(ke->vp, NOTE_WRITE);
137				ke->omtime = attr.va_mtime;
138			}
139
140			if (attr.va_ctime.tv_sec != ke->octime.tv_sec
141			    || attr.va_ctime.tv_nsec != ke->octime.tv_nsec) {
142				VN_KNOTE(ke->vp, NOTE_ATTRIB);
143				ke->octime = attr.va_ctime;
144			}
145
146			if (attr.va_nlink != ke->onlink) {
147				VN_KNOTE(ke->vp, NOTE_LINK);
148				ke->onlink = attr.va_nlink;
149			}
150
151			lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL);
152			ke->flags &= ~KEVQ_BUSY;
153			if (ke->flags & KEVQ_WANT) {
154				ke->flags &= ~KEVQ_WANT;
155				wakeup(ke);
156			}
157		}
158
159		if (SLIST_EMPTY(&kevlist)) {
160			/* Nothing more to watch, exit */
161			pnfskq = NULL;
162			lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
163			kthread_exit(0);
164		}
165		lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
166
167		/* wait a while before checking for changes again */
168		tsleep(pnfskq, PSOCK, "nfskqpw",
169			NFS_MINATTRTIMO * hz / 2);
170
171	}
172}
173
174static void
175filt_nfsdetach(struct knote *kn)
176{
177	struct vnode *vp = (struct vnode *)kn->kn_hook;
178	struct kevq *ke;
179
180	/* XXXLUKEM lock the struct? */
181	SLIST_REMOVE(&vp->v_klist, kn, knote, kn_selnext);
182
183	/* Remove the vnode from watch list */
184	lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL);
185	SLIST_FOREACH(ke, &kevlist, kev_link) {
186		if (ke->vp == vp) {
187			while (ke->flags & KEVQ_BUSY) {
188				ke->flags |= KEVQ_WANT;
189				lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
190				(void) tsleep(ke, PSOCK, "nfskqdet", 0);
191				lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL);
192			}
193
194			if (ke->usecount > 1) {
195				/* keep, other kevents need this */
196				ke->usecount--;
197			} else {
198				/* last user, g/c */
199				SLIST_REMOVE(&kevlist, ke, kevq, kev_link);
200				FREE(ke, M_KEVENT);
201			}
202			break;
203		}
204	}
205	lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
206}
207
208static int
209filt_nfsread(struct knote *kn, long hint)
210{
211	struct vnode *vp = (struct vnode *)kn->kn_hook;
212
213	/*
214	 * filesystem is gone, so set the EOF flag and schedule
215	 * the knote for deletion.
216	 */
217	if (hint == NOTE_REVOKE) {
218		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
219		return (1);
220	}
221
222	/* XXXLUKEM lock the struct? */
223	kn->kn_data = vp->v_size - kn->kn_fp->f_offset;
224        return (kn->kn_data != 0);
225}
226
227static int
228filt_nfsvnode(struct knote *kn, long hint)
229{
230
231	if (kn->kn_sfflags & hint)
232		kn->kn_fflags |= hint;
233	if (hint == NOTE_REVOKE) {
234		kn->kn_flags |= EV_EOF;
235		return (1);
236	}
237	return (kn->kn_fflags != 0);
238}
239
240static const struct filterops nfsread_filtops =
241	{ 1, NULL, filt_nfsdetach, filt_nfsread };
242static const struct filterops nfsvnode_filtops =
243	{ 1, NULL, filt_nfsdetach, filt_nfsvnode };
244
245int
246nfs_kqfilter(void *v)
247{
248	struct vop_kqfilter_args /* {
249		struct vnode	*a_vp;
250		struct knote	*a_kn;
251	} */ *ap = v;
252	struct vnode *vp;
253	struct knote *kn;
254	struct kevq *ke;
255	int error = 0;
256	struct vattr attr;
257	struct proc *p = curproc;	/* XXX */
258
259	vp = ap->a_vp;
260	kn = ap->a_kn;
261	switch (kn->kn_filter) {
262	case EVFILT_READ:
263		kn->kn_fop = &nfsread_filtops;
264		break;
265	case EVFILT_VNODE:
266		kn->kn_fop = &nfsvnode_filtops;
267		break;
268	default:
269		return (1);
270	}
271
272	kn->kn_hook = vp;
273
274	/*
275	 * Put the vnode to watched list.
276	 */
277
278	/*
279	 * Fetch current attributes. It's only needed when the vnode
280	 * is not watched yet, but we need to do this without lock
281	 * held. This is likely cheap due to attrcache, so do it now.
282	 */
283	memset(&attr, 0, sizeof(attr));
284	(void) VOP_GETATTR(vp, &attr, p->p_ucred, p);
285
286	lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL);
287
288	/* ensure the poller is running */
289	if (!pnfskq) {
290		error = kthread_create1(nfs_kqpoll, NULL, &pnfskq,
291				"nfskqpoll");
292		if (error)
293			goto out;
294	}
295
296	SLIST_FOREACH(ke, &kevlist, kev_link) {
297		if (ke->vp == vp)
298			break;
299	}
300
301	if (ke) {
302		/* already watched, so just bump usecount */
303		ke->usecount++;
304	} else {
305		/* need a new one */
306		MALLOC(ke, struct kevq *, sizeof(struct kevq), M_KEVENT,
307			M_WAITOK);
308		ke->vp = vp;
309		ke->usecount = 1;
310		ke->flags = 0;
311		ke->omtime = attr.va_mtime;
312		ke->octime = attr.va_ctime;
313		ke->onlink = attr.va_nlink;
314		SLIST_INSERT_HEAD(&kevlist, ke, kev_link);
315	}
316
317	/* kick the poller */
318	wakeup(pnfskq);
319
320	/* XXXLUKEM lock the struct? */
321	SLIST_INSERT_HEAD(&vp->v_klist, kn, kn_selnext);
322
323    out:
324	lockmgr(&nfskevq_lock, LK_RELEASE, NULL);
325
326	return (error);
327}
328