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/nfsclient/nfs_lock.c

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    1 /*-
    2  * Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   13  *    promote products derived from this software without specific prior
   14  *    written permission.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  *
   28  *      from BSDI nfs_lock.c,v 2.4 1998/12/14 23:49:56 jch Exp
   29  */
   30 
   31 #include <sys/cdefs.h>
   32 __FBSDID("$FreeBSD: releng/5.3/sys/nfsclient/nfs_lock.c 122698 2003-11-14 20:54:10Z alfred $");
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/fcntl.h>
   37 #include <sys/kernel.h>         /* for hz */
   38 #include <sys/limits.h>
   39 #include <sys/lock.h>
   40 #include <sys/malloc.h>
   41 #include <sys/lockf.h>          /* for hz */ /* Must come after sys/malloc.h */
   42 #include <sys/mbuf.h>
   43 #include <sys/mount.h>
   44 #include <sys/namei.h>
   45 #include <sys/proc.h>
   46 #include <sys/resourcevar.h>
   47 #include <sys/socket.h>
   48 #include <sys/socket.h>
   49 #include <sys/unistd.h>
   50 #include <sys/vnode.h>
   51 
   52 #include <net/if.h>
   53 
   54 #include <rpc/rpcclnt.h>
   55 
   56 #include <nfs/rpcv2.h>
   57 #include <nfs/nfsproto.h>
   58 #include <nfsclient/nfs.h>
   59 #include <nfsclient/nfsmount.h>
   60 #include <nfsclient/nfsnode.h>
   61 #include <nfsclient/nfs_lock.h>
   62 #include <nfsclient/nlminfo.h>
   63 
   64 /*
   65  * XXX
   66  * We have to let the process know if the call succeeded.  I'm using an extra
   67  * field in the p_nlminfo field in the proc structure, as it is already for
   68  * lockd stuff.
   69  */
   70 
   71 /*
   72  * nfs_advlock --
   73  *      NFS advisory byte-level locks.
   74  */
   75 int
   76 nfs_dolock(struct vop_advlock_args *ap)
   77 {
   78         LOCKD_MSG msg;
   79         struct nameidata nd;
   80         struct thread *td;
   81         struct vnode *vp, *wvp;
   82         int error, error1;
   83         struct flock *fl;
   84         int fmode, ioflg;
   85         struct proc *p;
   86 
   87         td = curthread;
   88         p = td->td_proc;
   89 
   90         vp = ap->a_vp;
   91         fl = ap->a_fl;
   92 
   93         /*
   94          * the NLM protocol doesn't allow the server to return an error
   95          * on ranges, so we do it.
   96          */
   97         if (fl->l_whence != SEEK_END) {
   98                 if ((fl->l_whence != SEEK_CUR && fl->l_whence != SEEK_SET) ||
   99                     fl->l_start < 0 ||
  100                     (fl->l_len < 0 &&
  101                      (fl->l_start == 0 || fl->l_start + fl->l_len < 0)))
  102                         return (EINVAL);
  103                 if (fl->l_len > 0 &&
  104                          (fl->l_len - 1 > OFF_MAX - fl->l_start))
  105                         return (EOVERFLOW);
  106         }
  107 
  108         /*
  109          * Fill in the information structure.
  110          */
  111         msg.lm_version = LOCKD_MSG_VERSION;
  112         msg.lm_msg_ident.pid = p->p_pid;
  113         /*
  114          * if there is no nfsowner table yet, allocate one.
  115          */
  116         if (p->p_nlminfo == NULL) {
  117                 MALLOC(p->p_nlminfo, struct nlminfo *,
  118                         sizeof(struct nlminfo), M_LOCKF, M_WAITOK | M_ZERO);
  119                 p->p_nlminfo->pid_start = p->p_stats->p_start;
  120                 timevaladd(&p->p_nlminfo->pid_start, &boottime);
  121         }
  122         msg.lm_msg_ident.pid_start = p->p_nlminfo->pid_start;
  123         msg.lm_msg_ident.msg_seq = ++(p->p_nlminfo->msg_seq);
  124 
  125         msg.lm_fl = *fl;
  126         msg.lm_wait = ap->a_flags & F_WAIT;
  127         msg.lm_getlk = ap->a_op == F_GETLK;
  128         bcopy(VFSTONFS(vp->v_mount)->nm_nam, &msg.lm_addr,
  129                 min(sizeof msg.lm_addr, VFSTONFS(vp->v_mount)->nm_nam->sa_len));
  130         msg.lm_fh_len = NFS_ISV3(vp) ? VTONFS(vp)->n_fhsize : NFSX_V2FH;
  131         bcopy(VTONFS(vp)->n_fhp, msg.lm_fh, msg.lm_fh_len);
  132         msg.lm_nfsv3 = NFS_ISV3(vp);
  133         cru2x(td->td_ucred, &msg.lm_cred);
  134 
  135         /*
  136          * Open the lock fifo.  If for any reason we don't find the fifo, it
  137          * means that the lock daemon isn't running.  Translate any missing
  138          * file error message for the user, otherwise the application will
  139          * complain that the user's file is missing, which isn't the case.
  140          * Note that we use proc0's cred, so the fifo is opened as root.
  141          *
  142          * XXX: Note that this behavior is relative to the root directory
  143          * of the current process, and this may result in a variety of
  144          * {functional, security} problems in chroot() environments.
  145          */
  146         NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, _PATH_LCKFIFO, td);
  147 
  148         fmode = FFLAGS(O_WRONLY | O_NONBLOCK);
  149         error = vn_open_cred(&nd, &fmode, 0, thread0.td_ucred, -1);
  150         switch (error) {
  151         case ENOENT:
  152         case ENXIO:
  153                 /*
  154                  * Map a failure to find the fifo or no listener on the
  155                  * fifo to locking not being supported.
  156                  */
  157                 return (EOPNOTSUPP);
  158         case 0:
  159                 break;
  160         default:
  161                 return (error);
  162         }
  163         wvp = nd.ni_vp;
  164         VOP_UNLOCK(wvp, 0, td);         /* vn_open leaves it locked */
  165 
  166 
  167         ioflg = IO_UNIT | IO_NOMACCHECK;
  168         for (;;) {
  169                 VOP_LEASE(wvp, td, thread0.td_ucred, LEASE_WRITE);
  170 
  171                 error = vn_rdwr(UIO_WRITE, wvp, (caddr_t)&msg, sizeof(msg), 0,
  172                     UIO_SYSSPACE, ioflg, thread0.td_ucred, NOCRED, NULL, td);
  173 
  174                 if (error && (((ioflg & IO_NDELAY) == 0) || error != EAGAIN)) {
  175                         break;
  176                 }
  177                 /*
  178                  * If we're locking a file, wait for an answer.  Unlocks succeed
  179                  * immediately.
  180                  */
  181                 if (fl->l_type == F_UNLCK)
  182                         /*
  183                          * XXX this isn't exactly correct.  The client side
  184                          * needs to continue sending it's unlock until
  185                          * it gets a responce back.
  186                          */
  187                         break;
  188 
  189                 /*
  190                  * retry after 20 seconds if we haven't gotten a responce yet.
  191                  * This number was picked out of thin air... but is longer
  192                  * then even a reasonably loaded system should take (at least
  193                  * on a local network).  XXX Probably should use a back-off
  194                  * scheme.
  195                  *
  196                  * XXX: No PCATCH here since we currently have no useful
  197                  * way to signal to the userland rpc.lockd that the request
  198                  * has been aborted.  Once the rpc.lockd implementation
  199                  * can handle aborts, and we report them properly,
  200                  * PCATCH can be put back.  In the mean time, if we did
  201                  * permit aborting, the lock attempt would "get lost"
  202                  * and the lock would get stuck in the locked state.
  203                  */
  204                 error = tsleep(p->p_nlminfo, PUSER, "lockd", 20*hz);
  205                 if (error != 0) {
  206                         if (error == EWOULDBLOCK) {
  207                                 /*
  208                                  * We timed out, so we rewrite the request
  209                                  * to the fifo, but only if it isn't already
  210                                  * full.
  211                                  */
  212                                 ioflg |= IO_NDELAY;
  213                                 continue;
  214                         }
  215 
  216                         break;
  217                 }
  218 
  219                 if (msg.lm_getlk && p->p_nlminfo->retcode == 0) {
  220                         if (p->p_nlminfo->set_getlk_pid) {
  221                                 fl->l_pid = p->p_nlminfo->getlk_pid;
  222                         } else {
  223                                 fl->l_type = F_UNLCK;
  224                         }
  225                 }
  226                 error = p->p_nlminfo->retcode;
  227                 break;
  228         }
  229 
  230         error1 = vn_close(wvp, FWRITE, thread0.td_ucred, td);
  231         /* prefer any previous 'error' to our vn_close 'error1'. */
  232         return (error != 0 ? error : error1);
  233 }
  234 
  235 /*
  236  * nfslockdans --
  237  *      NFS advisory byte-level locks answer from the lock daemon.
  238  */
  239 int
  240 nfslockdans(struct thread *td, struct lockd_ans *ansp)
  241 {
  242         struct proc *targetp;
  243         int error;
  244 
  245         /* Let root, or someone who once was root (lockd generally
  246          * switches to the daemon uid once it is done setting up) make
  247          * this call.
  248          *
  249          * XXX This authorization check is probably not right.
  250          */
  251         if ((error = suser(td)) != 0 &&
  252             td->td_ucred->cr_svuid != 0)
  253                 return (error);
  254 
  255         /* the version should match, or we're out of sync */
  256         if (ansp->la_vers != LOCKD_ANS_VERSION)
  257                 return (EINVAL);
  258 
  259         /* Find the process, set its return errno and wake it up. */
  260         if ((targetp = pfind(ansp->la_msg_ident.pid)) == NULL)
  261                 return (ESRCH);
  262 
  263         /* verify the pid hasn't been reused (if we can), and it isn't waiting
  264          * for an answer from a more recent request.  We return an EPIPE if
  265          * the match fails, because we've already used ESRCH above, and this
  266          * is sort of like writing on a pipe after the reader has closed it.
  267          */
  268         if (targetp->p_nlminfo == NULL ||
  269             ((ansp->la_msg_ident.msg_seq != -1) &&
  270               (timevalcmp(&targetp->p_nlminfo->pid_start,
  271                         &ansp->la_msg_ident.pid_start, !=) ||
  272                targetp->p_nlminfo->msg_seq != ansp->la_msg_ident.msg_seq))) {
  273                 PROC_UNLOCK(targetp);
  274                 return (EPIPE);
  275         }
  276 
  277         targetp->p_nlminfo->retcode = ansp->la_errno;
  278         targetp->p_nlminfo->set_getlk_pid = ansp->la_set_getlk_pid;
  279         targetp->p_nlminfo->getlk_pid = ansp->la_getlk_pid;
  280 
  281         wakeup(targetp->p_nlminfo);
  282 
  283         PROC_UNLOCK(targetp);
  284         return (0);
  285 }

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