nfs_kq.c

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    1 /*      $NetBSD: nfs_kq.c,v 1.22 2008/04/28 20:24:10 martin Exp $       */
    2 
    3 /*-
    4  * Copyright (c) 2002, 2008 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  *
   19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   29  * POSSIBILITY OF SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __KERNEL_RCSID(0, "$NetBSD: nfs_kq.c,v 1.22 2008/04/28 20:24:10 martin Exp $");
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/condvar.h>
   38 #include <sys/kernel.h>
   39 #include <sys/proc.h>
   40 #include <sys/kmem.h>
   41 #include <sys/mount.h>
   42 #include <sys/mutex.h>
   43 #include <sys/vnode.h>
   44 #include <sys/unistd.h>
   45 #include <sys/file.h>
   46 #include <sys/kthread.h>
   47 
   48 #include <uvm/uvm_extern.h>
   49 #include <uvm/uvm.h>
   50 
   51 #include <nfs/rpcv2.h>
   52 #include <nfs/nfsproto.h>
   53 #include <nfs/nfs.h>
   54 #include <nfs/nfsnode.h>
   55 #include <nfs/nfs_var.h>
   56 
   57 struct kevq {
   58         SLIST_ENTRY(kevq)       kev_link;
   59         struct vnode            *vp;
   60         u_int                   usecount;
   61         u_int                   flags;
   62 #define KEVQ_BUSY       0x01    /* currently being processed */
   63         struct timespec         omtime; /* old modification time */
   64         struct timespec         octime; /* old change time */
   65         nlink_t                 onlink; /* old number of references to file */
   66         kcondvar_t              cv;
   67 };
   68 SLIST_HEAD(kevqlist, kevq);
   69 
   70 static kmutex_t nfskevq_lock;
   71 static struct lwp *nfskq_thread;
   72 static kcondvar_t nfskq_cv;
   73 static struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist);
   74 
   75 void
   76 nfs_kqinit(void)
   77 {
   78 
   79         mutex_init(&nfskevq_lock, MUTEX_DEFAULT, IPL_NONE);
   80         cv_init(&nfskq_cv, "nfskqpw");
   81 }
   82 
   83 /*
   84  * This quite simplistic routine periodically checks for server changes
   85  * of any of the watched files every NFS_MINATTRTIMO/2 seconds.
   86  * Only changes in size, modification time, change time and nlinks
   87  * are being checked, everything else is ignored.
   88  * The routine only calls VOP_GETATTR() when it's likely it would get
   89  * some new data, i.e. when the vnode expires from attrcache. This
   90  * should give same result as periodically running stat(2) from userland,
   91  * while keeping CPU/network usage low, and still provide proper kevent
   92  * semantics.
   93  * The poller thread is created when first vnode is added to watch list,
   94  * and exits when the watch list is empty. The overhead of thread creation
   95  * isn't really important, neither speed of attach and detach of knote.
   96  */
   97 /* ARGSUSED */
   98 static void
   99 nfs_kqpoll(void *arg)
  100 {
  101         struct kevq *ke;
  102         struct vattr attr;
  103         struct lwp *l = curlwp;
  104         u_quad_t osize;
  105 
  106         mutex_enter(&nfskevq_lock);
  107         for (;;) {
  108                 SLIST_FOREACH(ke, &kevlist, kev_link) {
  109                         /* skip if still in attrcache */
  110                         if (nfs_getattrcache(ke->vp, &attr) != ENOENT)
  111                                 continue;
  112 
  113                         /*
  114                          * Mark entry busy, release lock and check
  115                          * for changes.
  116                          */
  117                         ke->flags |= KEVQ_BUSY;
  118                         mutex_exit(&nfskevq_lock);
  119 
  120                         /* save v_size, nfs_getattr() updates it */
  121                         osize = ke->vp->v_size;
  122 
  123                         (void) VOP_GETATTR(ke->vp, &attr, l->l_cred);
  124 
  125                         /* following is a bit fragile, but about best
  126                          * we can get */
  127                         if (attr.va_size != osize) {
  128                                 int extended = (attr.va_size > osize);
  129                                 VN_KNOTE(ke->vp, NOTE_WRITE
  130                                         | (extended ? NOTE_EXTEND : 0));
  131                                 ke->omtime = attr.va_mtime;
  132                         } else if (attr.va_mtime.tv_sec != ke->omtime.tv_sec
  133                             || attr.va_mtime.tv_nsec != ke->omtime.tv_nsec) {
  134                                 VN_KNOTE(ke->vp, NOTE_WRITE);
  135                                 ke->omtime = attr.va_mtime;
  136                         }
  137 
  138                         if (attr.va_ctime.tv_sec != ke->octime.tv_sec
  139                             || attr.va_ctime.tv_nsec != ke->octime.tv_nsec) {
  140                                 VN_KNOTE(ke->vp, NOTE_ATTRIB);
  141                                 ke->octime = attr.va_ctime;
  142                         }
  143 
  144                         if (attr.va_nlink != ke->onlink) {
  145                                 VN_KNOTE(ke->vp, NOTE_LINK);
  146                                 ke->onlink = attr.va_nlink;
  147                         }
  148 
  149                         mutex_enter(&nfskevq_lock);
  150                         ke->flags &= ~KEVQ_BUSY;
  151                         cv_signal(&ke->cv);
  152                 }
  153 
  154                 if (SLIST_EMPTY(&kevlist)) {
  155                         /* Nothing more to watch, exit */
  156                         nfskq_thread = NULL;
  157                         mutex_exit(&nfskevq_lock);
  158                         kthread_exit(0);
  159                 }
  160 
  161                 /* wait a while before checking for changes again */
  162                 cv_timedwait(&nfskq_cv, &nfskevq_lock,
  163                     NFS_MINATTRTIMO * hz / 2);
  164         }
  165 }
  166 
  167 static void
  168 filt_nfsdetach(struct knote *kn)
  169 {
  170         struct vnode *vp = (struct vnode *)kn->kn_hook;
  171         struct kevq *ke;
  172 
  173         mutex_enter(&vp->v_interlock);
  174         SLIST_REMOVE(&vp->v_klist, kn, knote, kn_selnext);
  175         mutex_exit(&vp->v_interlock);
  176 
  177         /* Remove the vnode from watch list */
  178         mutex_enter(&nfskevq_lock);
  179         SLIST_FOREACH(ke, &kevlist, kev_link) {
  180                 if (ke->vp == vp) {
  181                         while (ke->flags & KEVQ_BUSY) {
  182                                 cv_wait(&ke->cv, &nfskevq_lock);
  183                         }
  184 
  185                         if (ke->usecount > 1) {
  186                                 /* keep, other kevents need this */
  187                                 ke->usecount--;
  188                         } else {
  189                                 /* last user, g/c */
  190                                 cv_destroy(&ke->cv);
  191                                 SLIST_REMOVE(&kevlist, ke, kevq, kev_link);
  192                                 kmem_free(ke, sizeof(*ke));
  193                         }
  194                         break;
  195                 }
  196         }
  197         mutex_exit(&nfskevq_lock);
  198 }
  199 
  200 static int
  201 filt_nfsread(struct knote *kn, long hint)
  202 {
  203         struct vnode *vp = (struct vnode *)kn->kn_hook;
  204         int rv;
  205 
  206         /*
  207          * filesystem is gone, so set the EOF flag and schedule
  208          * the knote for deletion.
  209          */
  210         switch (hint) {
  211         case NOTE_REVOKE:
  212                 KASSERT(mutex_owned(&vp->v_interlock));
  213                 kn->kn_flags |= (EV_EOF | EV_ONESHOT);
  214                 return (1);
  215         case 0:
  216                 mutex_enter(&vp->v_interlock);
  217                 kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset;
  218                 rv = (kn->kn_data != 0);
  219                 mutex_exit(&vp->v_interlock);
  220                 return rv;
  221         default:
  222                 KASSERT(mutex_owned(&vp->v_interlock));
  223                 kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset;
  224                 return (kn->kn_data != 0);
  225         }
  226 }
  227 
  228 static int
  229 filt_nfsvnode(struct knote *kn, long hint)
  230 {
  231         struct vnode *vp = (struct vnode *)kn->kn_hook;
  232         int fflags;
  233 
  234         switch (hint) {
  235         case NOTE_REVOKE:
  236                 KASSERT(mutex_owned(&vp->v_interlock));
  237                 kn->kn_flags |= EV_EOF;
  238                 if ((kn->kn_sfflags & hint) != 0)
  239                         kn->kn_fflags |= hint;
  240                 return (1);
  241         case 0:
  242                 mutex_enter(&vp->v_interlock);
  243                 fflags = kn->kn_fflags;
  244                 mutex_exit(&vp->v_interlock);
  245                 break;
  246         default:
  247                 KASSERT(mutex_owned(&vp->v_interlock));
  248                 if ((kn->kn_sfflags & hint) != 0)
  249                         kn->kn_fflags |= hint;
  250                 fflags = kn->kn_fflags;
  251                 break;
  252         }
  253 
  254         return (fflags != 0);
  255 }
  256 
  257 
  258 static const struct filterops nfsread_filtops =
  259         { 1, NULL, filt_nfsdetach, filt_nfsread };
  260 static const struct filterops nfsvnode_filtops =
  261         { 1, NULL, filt_nfsdetach, filt_nfsvnode };
  262 
  263 int
  264 nfs_kqfilter(void *v)
  265 {
  266         struct vop_kqfilter_args /* {
  267                 struct vnode    *a_vp;
  268                 struct knote    *a_kn;
  269         } */ *ap = v;
  270         struct vnode *vp;
  271         struct knote *kn;
  272         struct kevq *ke;
  273         int error = 0;
  274         struct vattr attr;
  275         struct lwp *l = curlwp;
  276 
  277         vp = ap->a_vp;
  278         kn = ap->a_kn;
  279         switch (kn->kn_filter) {
  280         case EVFILT_READ:
  281                 kn->kn_fop = &nfsread_filtops;
  282                 break;
  283         case EVFILT_VNODE:
  284                 kn->kn_fop = &nfsvnode_filtops;
  285                 break;
  286         default:
  287                 return (EINVAL);
  288         }
  289 
  290         /*
  291          * Put the vnode to watched list.
  292          */
  293 
  294         /*
  295          * Fetch current attributes. It's only needed when the vnode
  296          * is not watched yet, but we need to do this without lock
  297          * held. This is likely cheap due to attrcache, so do it now.
  298          */
  299         memset(&attr, 0, sizeof(attr));
  300         (void) VOP_GETATTR(vp, &attr, l->l_cred);
  301 
  302         mutex_enter(&nfskevq_lock);
  303 
  304         /* ensure the poller is running */
  305         if (!nfskq_thread) {
  306                 error = kthread_create(PRI_NONE, 0, NULL, nfs_kqpoll,
  307                     NULL, &nfskq_thread, "nfskqpoll");
  308                 if (error) {
  309                         mutex_exit(&nfskevq_lock);
  310                         return error;
  311                 }
  312         }
  313 
  314         SLIST_FOREACH(ke, &kevlist, kev_link) {
  315                 if (ke->vp == vp)
  316                         break;
  317         }
  318 
  319         if (ke) {
  320                 /* already watched, so just bump usecount */
  321                 ke->usecount++;
  322         } else {
  323                 /* need a new one */
  324                 ke = kmem_alloc(sizeof(*ke), KM_SLEEP);
  325                 ke->vp = vp;
  326                 ke->usecount = 1;
  327                 ke->flags = 0;
  328                 ke->omtime = attr.va_mtime;
  329                 ke->octime = attr.va_ctime;
  330                 ke->onlink = attr.va_nlink;
  331                 cv_init(&ke->cv, "nfskqdet");
  332                 SLIST_INSERT_HEAD(&kevlist, ke, kev_link);
  333         }
  334 
  335         mutex_enter(&vp->v_interlock);
  336         SLIST_INSERT_HEAD(&vp->v_klist, kn, kn_selnext);
  337         kn->kn_hook = vp;
  338         mutex_exit(&vp->v_interlock);
  339 
  340         /* kick the poller */
  341         cv_signal(&nfskq_cv);
  342         mutex_exit(&nfskevq_lock);
  343 
  344 
  345         return (error);
  346 }
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FreeBSD/Linux Kernel Cross Reference sys/nfs/nfs_kq.c

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sys/nfs/nfs_kq.c
