The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/nfsclient/nfs_clnfsiod.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1989, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * Rick Macklem at The University of Guelph.
    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. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      from nfs_syscalls.c     8.5 (Berkeley) 3/30/95
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: stable/12/sys/fs/nfsclient/nfs_clnfsiod.c 354164 2019-10-30 01:57:40Z rmacklem $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/sysproto.h>
   43 #include <sys/kernel.h>
   44 #include <sys/sysctl.h>
   45 #include <sys/file.h>
   46 #include <sys/vnode.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mount.h>
   49 #include <sys/proc.h>
   50 #include <sys/bio.h>
   51 #include <sys/buf.h>
   52 #include <sys/mbuf.h>
   53 #include <sys/socket.h>
   54 #include <sys/socketvar.h>
   55 #include <sys/domain.h>
   56 #include <sys/protosw.h>
   57 #include <sys/namei.h>
   58 #include <sys/unistd.h>
   59 #include <sys/kthread.h>
   60 #include <sys/fcntl.h>
   61 #include <sys/lockf.h>
   62 #include <sys/mutex.h>
   63 #include <sys/taskqueue.h>
   64 
   65 #include <netinet/in.h>
   66 #include <netinet/tcp.h>
   67 
   68 #include <fs/nfs/nfsport.h>
   69 #include <fs/nfsclient/nfsmount.h>
   70 #include <fs/nfsclient/nfs.h>
   71 #include <fs/nfsclient/nfsnode.h>
   72 
   73 extern struct mtx       ncl_iod_mutex;
   74 extern struct task      ncl_nfsiodnew_task;
   75 
   76 int ncl_numasync;
   77 enum nfsiod_state ncl_iodwant[NFS_MAXASYNCDAEMON];
   78 struct nfsmount *ncl_iodmount[NFS_MAXASYNCDAEMON];
   79 
   80 static void     nfssvc_iod(void *);
   81 
   82 static int nfs_asyncdaemon[NFS_MAXASYNCDAEMON];
   83 
   84 SYSCTL_DECL(_vfs_nfs);
   85 
   86 /* Maximum number of seconds a nfsiod kthread will sleep before exiting */
   87 static unsigned int nfs_iodmaxidle = 120;
   88 SYSCTL_UINT(_vfs_nfs, OID_AUTO, iodmaxidle, CTLFLAG_RW, &nfs_iodmaxidle, 0,
   89     "Max number of seconds an nfsiod kthread will sleep before exiting");
   90 
   91 /* Maximum number of nfsiod kthreads */
   92 unsigned int ncl_iodmax = 20;
   93 
   94 /* Minimum number of nfsiod kthreads to keep as spares */
   95 static unsigned int nfs_iodmin = 0;
   96 
   97 static int nfs_nfsiodnew_sync(void);
   98 
   99 static int
  100 sysctl_iodmin(SYSCTL_HANDLER_ARGS)
  101 {
  102         int error, i;
  103         int newmin;
  104 
  105         newmin = nfs_iodmin;
  106         error = sysctl_handle_int(oidp, &newmin, 0, req);
  107         if (error || (req->newptr == NULL))
  108                 return (error);
  109         NFSLOCKIOD();
  110         if (newmin > ncl_iodmax) {
  111                 error = EINVAL;
  112                 goto out;
  113         }
  114         nfs_iodmin = newmin;
  115         if (ncl_numasync >= nfs_iodmin)
  116                 goto out;
  117         /*
  118          * If the current number of nfsiod is lower
  119          * than the new minimum, create some more.
  120          */
  121         for (i = nfs_iodmin - ncl_numasync; i > 0; i--)
  122                 nfs_nfsiodnew_sync();
  123 out:
  124         NFSUNLOCKIOD(); 
  125         return (0);
  126 }
  127 SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmin, CTLTYPE_UINT | CTLFLAG_RW, 0,
  128     sizeof (nfs_iodmin), sysctl_iodmin, "IU",
  129     "Min number of nfsiod kthreads to keep as spares");
  130 
  131 static int
  132 sysctl_iodmax(SYSCTL_HANDLER_ARGS)
  133 {
  134         int error, i;
  135         int iod, newmax;
  136 
  137         newmax = ncl_iodmax;
  138         error = sysctl_handle_int(oidp, &newmax, 0, req);
  139         if (error || (req->newptr == NULL))
  140                 return (error);
  141         if (newmax > NFS_MAXASYNCDAEMON)
  142                 return (EINVAL);
  143         NFSLOCKIOD();
  144         ncl_iodmax = newmax;
  145         if (ncl_numasync <= ncl_iodmax)
  146                 goto out;
  147         /*
  148          * If there are some asleep nfsiods that should
  149          * exit, wakeup() them so that they check ncl_iodmax
  150          * and exit.  Those who are active will exit as
  151          * soon as they finish I/O.
  152          */
  153         iod = ncl_numasync - 1;
  154         for (i = 0; i < ncl_numasync - ncl_iodmax; i++) {
  155                 if (ncl_iodwant[iod] == NFSIOD_AVAILABLE)
  156                         wakeup(&ncl_iodwant[iod]);
  157                 iod--;
  158         }
  159 out:
  160         NFSUNLOCKIOD();
  161         return (0);
  162 }
  163 SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmax, CTLTYPE_UINT | CTLFLAG_RW, 0,
  164     sizeof (ncl_iodmax), sysctl_iodmax, "IU",
  165     "Max number of nfsiod kthreads");
  166 
  167 static int
  168 nfs_nfsiodnew_sync(void)
  169 {
  170         int error, i;
  171 
  172         NFSASSERTIOD();
  173         for (i = 0; i < ncl_iodmax; i++) {
  174                 if (nfs_asyncdaemon[i] == 0) {
  175                         nfs_asyncdaemon[i] = 1;
  176                         break;
  177                 }
  178         }
  179         if (i == ncl_iodmax)
  180                 return (0);
  181         NFSUNLOCKIOD();
  182         error = kproc_create(nfssvc_iod, nfs_asyncdaemon + i, NULL,
  183             RFHIGHPID, 0, "newnfs %d", i);
  184         NFSLOCKIOD();
  185         if (error == 0) {
  186                 ncl_numasync++;
  187                 ncl_iodwant[i] = NFSIOD_AVAILABLE;
  188         } else
  189                 nfs_asyncdaemon[i] = 0;
  190         return (error);
  191 }
  192 
  193 void
  194 ncl_nfsiodnew_tq(__unused void *arg, int pending)
  195 {
  196 
  197         NFSLOCKIOD();
  198         while (pending > 0) {
  199                 pending--;
  200                 nfs_nfsiodnew_sync();
  201         }
  202         NFSUNLOCKIOD();
  203 }
  204 
  205 void
  206 ncl_nfsiodnew(void)
  207 {
  208 
  209         NFSASSERTIOD();
  210         taskqueue_enqueue(taskqueue_thread, &ncl_nfsiodnew_task);
  211 }
  212 
  213 static void
  214 nfsiod_setup(void *dummy)
  215 {
  216         int error;
  217 
  218         TUNABLE_INT_FETCH("vfs.nfs.iodmin", &nfs_iodmin);
  219         nfscl_init();
  220         NFSLOCKIOD();
  221         /* Silently limit the start number of nfsiod's */
  222         if (nfs_iodmin > NFS_MAXASYNCDAEMON)
  223                 nfs_iodmin = NFS_MAXASYNCDAEMON;
  224 
  225         while (ncl_numasync < nfs_iodmin) {
  226                 error = nfs_nfsiodnew_sync();
  227                 if (error == -1)
  228                         panic("nfsiod_setup: nfs_nfsiodnew failed");
  229         }
  230         NFSUNLOCKIOD();
  231 }
  232 SYSINIT(newnfsiod, SI_SUB_KTHREAD_IDLE, SI_ORDER_ANY, nfsiod_setup, NULL);
  233 
  234 static int nfs_defect = 0;
  235 SYSCTL_INT(_vfs_nfs, OID_AUTO, defect, CTLFLAG_RW, &nfs_defect, 0,
  236     "Allow nfsiods to migrate serving different mounts");
  237 
  238 /*
  239  * Asynchronous I/O daemons for client nfs.
  240  * They do read-ahead and write-behind operations on the block I/O cache.
  241  * Returns if we hit the timeout defined by the iodmaxidle sysctl.
  242  */
  243 static void
  244 nfssvc_iod(void *instance)
  245 {
  246         struct buf *bp;
  247         struct nfsmount *nmp;
  248         int myiod, timo;
  249         int error = 0;
  250 
  251         NFSLOCKIOD();
  252         myiod = (int *)instance - nfs_asyncdaemon;
  253         /*
  254          * Main loop
  255          */
  256         for (;;) {
  257             while (((nmp = ncl_iodmount[myiod]) == NULL)
  258                    || !TAILQ_FIRST(&nmp->nm_bufq)) {
  259                 if (myiod >= ncl_iodmax)
  260                         goto finish;
  261                 if (nmp)
  262                         nmp->nm_bufqiods--;
  263                 if (ncl_iodwant[myiod] == NFSIOD_NOT_AVAILABLE)
  264                         ncl_iodwant[myiod] = NFSIOD_AVAILABLE;
  265                 ncl_iodmount[myiod] = NULL;
  266                 /*
  267                  * Always keep at least nfs_iodmin kthreads.
  268                  */
  269                 timo = (myiod < nfs_iodmin) ? 0 : nfs_iodmaxidle * hz;
  270                 error = msleep(&ncl_iodwant[myiod], &ncl_iod_mutex, PWAIT | PCATCH,
  271                     "-", timo);
  272                 if (error) {
  273                         nmp = ncl_iodmount[myiod];
  274                         /*
  275                          * Rechecking the nm_bufq closes a rare race where the 
  276                          * nfsiod is woken up at the exact time the idle timeout
  277                          * fires
  278                          */
  279                         if (nmp && TAILQ_FIRST(&nmp->nm_bufq))
  280                                 error = 0;
  281                         break;
  282                 }
  283             }
  284             if (error)
  285                     break;
  286             while ((bp = TAILQ_FIRST(&nmp->nm_bufq)) != NULL) {
  287                 /* Take one off the front of the list */
  288                 TAILQ_REMOVE(&nmp->nm_bufq, bp, b_freelist);
  289                 nmp->nm_bufqlen--;
  290                 if (nmp->nm_bufqwant && nmp->nm_bufqlen <= ncl_numasync) {
  291                     nmp->nm_bufqwant = 0;
  292                     wakeup(&nmp->nm_bufq);
  293                 }
  294                 NFSUNLOCKIOD();
  295                 if (bp->b_flags & B_DIRECT) {
  296                         KASSERT((bp->b_iocmd == BIO_WRITE), ("nfscvs_iod: BIO_WRITE not set"));
  297                         (void)ncl_doio_directwrite(bp);
  298                 } else {
  299                         if (bp->b_iocmd == BIO_READ)
  300                                 (void) ncl_doio(bp->b_vp, bp, bp->b_rcred,
  301                                     NULL, 0);
  302                         else
  303                                 (void) ncl_doio(bp->b_vp, bp, bp->b_wcred,
  304                                     NULL, 0);
  305                 }
  306                 NFSLOCKIOD();
  307                 /*
  308                  * Make sure the nmp hasn't been dismounted as soon as
  309                  * ncl_doio() completes for the last buffer.
  310                  */
  311                 nmp = ncl_iodmount[myiod];
  312                 if (nmp == NULL)
  313                         break;
  314 
  315                 /*
  316                  * If there are more than one iod on this mount, then defect
  317                  * so that the iods can be shared out fairly between the mounts
  318                  */
  319                 if (nfs_defect && nmp->nm_bufqiods > 1) {
  320                     NFS_DPF(ASYNCIO,
  321                             ("nfssvc_iod: iod %d defecting from mount %p\n",
  322                              myiod, nmp));
  323                     ncl_iodmount[myiod] = NULL;
  324                     nmp->nm_bufqiods--;
  325                     break;
  326                 }
  327             }
  328         }
  329 finish:
  330         nfs_asyncdaemon[myiod] = 0;
  331         if (nmp)
  332             nmp->nm_bufqiods--;
  333         ncl_iodwant[myiod] = NFSIOD_NOT_AVAILABLE;
  334         ncl_iodmount[myiod] = NULL;
  335         /* Someone may be waiting for the last nfsiod to terminate. */
  336         if (--ncl_numasync == 0)
  337                 wakeup(&ncl_numasync);
  338         NFSUNLOCKIOD();
  339         if ((error == 0) || (error == EWOULDBLOCK))
  340                 kproc_exit(0);
  341         /* Abnormal termination */
  342         kproc_exit(1);
  343 }

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