The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_vnops.c

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    1 /*      $OpenBSD: vfs_vnops.c,v 1.121 2022/08/14 01:58:28 jsg Exp $     */
    2 /*      $NetBSD: vfs_vnops.c,v 1.20 1996/02/04 02:18:41 christos Exp $  */
    3 
    4 /*
    5  * Copyright (c) 1982, 1986, 1989, 1993
    6  *      The Regents of the University of California.  All rights reserved.
    7  * (c) UNIX System Laboratories, Inc.
    8  * All or some portions of this file are derived from material licensed
    9  * to the University of California by American Telephone and Telegraph
   10  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   11  * the permission of UNIX System Laboratories, Inc.
   12  *
   13  * Redistribution and use in source and binary forms, with or without
   14  * modification, are permitted provided that the following conditions
   15  * are met:
   16  * 1. Redistributions of source code must retain the above copyright
   17  *    notice, this list of conditions and the following disclaimer.
   18  * 2. Redistributions in binary form must reproduce the above copyright
   19  *    notice, this list of conditions and the following disclaimer in the
   20  *    documentation and/or other materials provided with the distribution.
   21  * 3. Neither the name of the University nor the names of its contributors
   22  *    may be used to endorse or promote products derived from this software
   23  *    without specific prior written permission.
   24  *
   25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   35  * SUCH DAMAGE.
   36  *
   37  *      @(#)vfs_vnops.c 8.5 (Berkeley) 12/8/94
   38  */
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/malloc.h>
   43 #include <sys/fcntl.h>
   44 #include <sys/file.h>
   45 #include <sys/stat.h>
   46 #include <sys/proc.h>
   47 #include <sys/resourcevar.h>
   48 #include <sys/signalvar.h>
   49 #include <sys/mount.h>
   50 #include <sys/namei.h>
   51 #include <sys/lock.h>
   52 #include <sys/vnode.h>
   53 #include <sys/ioctl.h>
   54 #include <sys/tty.h>
   55 #include <sys/specdev.h>
   56 #include <sys/unistd.h>
   57 
   58 int vn_read(struct file *, struct uio *, int);
   59 int vn_write(struct file *, struct uio *, int);
   60 int vn_kqfilter(struct file *, struct knote *);
   61 int vn_closefile(struct file *, struct proc *);
   62 int vn_seek(struct file *, off_t *, int, struct proc *);
   63 
   64 const struct fileops vnops = {
   65         .fo_read        = vn_read,
   66         .fo_write       = vn_write,
   67         .fo_ioctl       = vn_ioctl,
   68         .fo_kqfilter    = vn_kqfilter,
   69         .fo_stat        = vn_statfile,
   70         .fo_close       = vn_closefile,
   71         .fo_seek        = vn_seek,
   72 };
   73 
   74 /*
   75  * Common code for vnode open operations.
   76  * Check permissions, and call the VOP_OPEN or VOP_CREATE routine.
   77  */
   78 int
   79 vn_open(struct nameidata *ndp, int fmode, int cmode)
   80 {
   81         struct vnode *vp;
   82         struct proc *p = ndp->ni_cnd.cn_proc;
   83         struct ucred *cred = p->p_ucred;
   84         struct vattr va;
   85         struct cloneinfo *cip;
   86         int error;
   87 
   88         /*
   89          * The only valid flag to pass in here from NDINIT is
   90          * KERNELPATH, This function will override the nameiop based
   91          * on the fmode and cmode flags, So validate that our caller
   92          * has not set other flags or operations in the nameidata
   93          * structure.
   94          */
   95         KASSERT(ndp->ni_cnd.cn_flags == 0 || ndp->ni_cnd.cn_flags == KERNELPATH);
   96         KASSERT(ndp->ni_cnd.cn_nameiop == 0);
   97 
   98         if ((fmode & (FREAD|FWRITE)) == 0)
   99                 return (EINVAL);
  100         if ((fmode & (O_TRUNC | FWRITE)) == O_TRUNC)
  101                 return (EINVAL);
  102         if (fmode & O_CREAT) {
  103                 ndp->ni_cnd.cn_nameiop = CREATE;
  104                 ndp->ni_cnd.cn_flags |= LOCKPARENT | LOCKLEAF;
  105                 if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0)
  106                         ndp->ni_cnd.cn_flags |= FOLLOW;
  107                 if ((error = namei(ndp)) != 0)
  108                         return (error);
  109 
  110                 if (ndp->ni_vp == NULL) {
  111                         VATTR_NULL(&va);
  112                         va.va_type = VREG;
  113                         va.va_mode = cmode;
  114                         if (fmode & O_EXCL)
  115                                 va.va_vaflags |= VA_EXCLUSIVE;
  116                         error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
  117                                            &ndp->ni_cnd, &va);
  118                         vput(ndp->ni_dvp);
  119                         if (error)
  120                                 return (error);
  121                         fmode &= ~O_TRUNC;
  122                         vp = ndp->ni_vp;
  123                 } else {
  124                         VOP_ABORTOP(ndp->ni_dvp, &ndp->ni_cnd);
  125                         if (ndp->ni_dvp == ndp->ni_vp)
  126                                 vrele(ndp->ni_dvp);
  127                         else
  128                                 vput(ndp->ni_dvp);
  129                         ndp->ni_dvp = NULL;
  130                         vp = ndp->ni_vp;
  131                         if (fmode & O_EXCL) {
  132                                 error = EEXIST;
  133                                 goto bad;
  134                         }
  135                         fmode &= ~O_CREAT;
  136                 }
  137         } else {
  138                 ndp->ni_cnd.cn_nameiop = LOOKUP;
  139                 ndp->ni_cnd.cn_flags |= ((fmode & O_NOFOLLOW) ? NOFOLLOW : FOLLOW) | LOCKLEAF;
  140                 if ((error = namei(ndp)) != 0)
  141                         return (error);
  142                 vp = ndp->ni_vp;
  143         }
  144         if (vp->v_type == VSOCK) {
  145                 error = EOPNOTSUPP;
  146                 goto bad;
  147         }
  148         if (vp->v_type == VLNK) {
  149                 error = ELOOP;
  150                 goto bad;
  151         }
  152         if ((fmode & O_DIRECTORY) && vp->v_type != VDIR) {
  153                 error = ENOTDIR;
  154                 goto bad;
  155         }
  156         if ((fmode & O_CREAT) == 0) {
  157                 if (fmode & FREAD) {
  158                         if ((error = VOP_ACCESS(vp, VREAD, cred, p)) != 0)
  159                                 goto bad;
  160                 }
  161                 if (fmode & FWRITE) {
  162                         if (vp->v_type == VDIR) {
  163                                 error = EISDIR;
  164                                 goto bad;
  165                         }
  166                         if ((error = vn_writechk(vp)) != 0 ||
  167                             (error = VOP_ACCESS(vp, VWRITE, cred, p)) != 0)
  168                                 goto bad;
  169                 }
  170         }
  171         if ((fmode & O_TRUNC) && vp->v_type == VREG) {
  172                 VATTR_NULL(&va);
  173                 va.va_size = 0;
  174                 if ((error = VOP_SETATTR(vp, &va, cred, p)) != 0)
  175                         goto bad;
  176         }
  177         if ((error = VOP_OPEN(vp, fmode, cred, p)) != 0)
  178                 goto bad;
  179 
  180         if (vp->v_flag & VCLONED) {
  181                 cip = (struct cloneinfo *)vp->v_data;
  182 
  183                 vp->v_flag &= ~VCLONED;
  184 
  185                 ndp->ni_vp = cip->ci_vp;        /* return cloned vnode */
  186                 vp->v_data = cip->ci_data;      /* restore v_data */
  187                 VOP_UNLOCK(vp);                 /* keep a reference */
  188                 vp = ndp->ni_vp;                /* for the increment below */
  189 
  190                 free(cip, M_TEMP, sizeof(*cip));
  191         }
  192 
  193         if (fmode & FWRITE)
  194                 vp->v_writecount++;
  195         return (0);
  196 bad:
  197         vput(vp);
  198         return (error);
  199 }
  200 
  201 /*
  202  * Check for write permissions on the specified vnode.
  203  * Prototype text segments cannot be written.
  204  */
  205 int
  206 vn_writechk(struct vnode *vp)
  207 {
  208         /*
  209          * Disallow write attempts on read-only file systems;
  210          * unless the file is a socket or a block or character
  211          * device resident on the file system.
  212          */
  213         if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_RDONLY)) {
  214                 switch (vp->v_type) {
  215                 case VREG:
  216                 case VDIR:
  217                 case VLNK:
  218                         return (EROFS);
  219                 case VNON:
  220                 case VCHR:
  221                 case VSOCK:
  222                 case VFIFO:
  223                 case VBAD:
  224                 case VBLK:
  225                         break;
  226                 }
  227         }
  228         /*
  229          * If there's shared text associated with
  230          * the vnode, try to free it up once.  If
  231          * we fail, we can't allow writing.
  232          */
  233         if ((vp->v_flag & VTEXT) && !uvm_vnp_uncache(vp))
  234                 return (ETXTBSY);
  235 
  236         return (0);
  237 }
  238 
  239 /*
  240  * Check whether a write operation would exceed the file size rlimit
  241  * for the process, if one should be applied for this operation.
  242  * If a partial write should take place, the uio is adjusted and the
  243  * amount by which the request would have exceeded the limit is returned
  244  * via the 'overrun' argument.
  245  */
  246 int
  247 vn_fsizechk(struct vnode *vp, struct uio *uio, int ioflag, ssize_t *overrun)
  248 {
  249         struct proc *p = uio->uio_procp;
  250 
  251         *overrun = 0;
  252         if (vp->v_type == VREG && p != NULL && !(ioflag & IO_NOLIMIT)) {
  253                 rlim_t limit = lim_cur_proc(p, RLIMIT_FSIZE);
  254 
  255                 /* if already at or over the limit, send the signal and fail */
  256                 if (uio->uio_offset >= limit) {
  257                         psignal(p, SIGXFSZ);
  258                         return (EFBIG);
  259                 }
  260 
  261                 /* otherwise, clamp the write to stay under the limit */
  262                 if (uio->uio_resid > limit - uio->uio_offset) {
  263                         *overrun = uio->uio_resid - (limit - uio->uio_offset);
  264                         uio->uio_resid = limit - uio->uio_offset;
  265                 }
  266         }
  267 
  268         return (0);
  269 }
  270 
  271 
  272 /*
  273  * Mark a vnode as being the text image of a running process.
  274  */
  275 void
  276 vn_marktext(struct vnode *vp)
  277 {
  278         vp->v_flag |= VTEXT;
  279 }
  280 
  281 /*
  282  * Vnode close call
  283  */
  284 int
  285 vn_close(struct vnode *vp, int flags, struct ucred *cred, struct proc *p)
  286 {
  287         int error;
  288 
  289         if (flags & FWRITE)
  290                 vp->v_writecount--;
  291         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  292         error = VOP_CLOSE(vp, flags, cred, p);
  293         vput(vp);
  294         return (error);
  295 }
  296 
  297 /*
  298  * Package up an I/O request on a vnode into a uio and do it.
  299  */
  300 int
  301 vn_rdwr(enum uio_rw rw, struct vnode *vp, caddr_t base, int len, off_t offset,
  302     enum uio_seg segflg, int ioflg, struct ucred *cred, size_t *aresid,
  303     struct proc *p)
  304 {
  305         struct uio auio;
  306         struct iovec aiov;
  307         int error;
  308 
  309         auio.uio_iov = &aiov;
  310         auio.uio_iovcnt = 1;
  311         aiov.iov_base = base;
  312         aiov.iov_len = len;
  313         auio.uio_resid = len;
  314         auio.uio_offset = offset;
  315         auio.uio_segflg = segflg;
  316         auio.uio_rw = rw;
  317         auio.uio_procp = p;
  318 
  319         if ((ioflg & IO_NODELOCKED) == 0)
  320                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  321         if (rw == UIO_READ) {
  322                 error = VOP_READ(vp, &auio, ioflg, cred);
  323         } else {
  324                 error = VOP_WRITE(vp, &auio, ioflg, cred);
  325         }
  326         if ((ioflg & IO_NODELOCKED) == 0)
  327                 VOP_UNLOCK(vp);
  328 
  329         if (aresid)
  330                 *aresid = auio.uio_resid;
  331         else
  332                 if (auio.uio_resid && error == 0)
  333                         error = EIO;
  334         return (error);
  335 }
  336 
  337 /*
  338  * File table vnode read routine.
  339  */
  340 int
  341 vn_read(struct file *fp, struct uio *uio, int fflags)
  342 {
  343         struct vnode *vp = fp->f_data;
  344         struct ucred *cred = fp->f_cred;
  345         size_t count = uio->uio_resid;
  346         off_t offset;
  347         int error;
  348 
  349         KERNEL_LOCK();
  350 
  351         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  352 
  353         if ((fflags & FO_POSITION) == 0)
  354                 offset = uio->uio_offset = fp->f_offset;
  355         else
  356                 offset = uio->uio_offset;
  357 
  358         /* no wrap around of offsets except on character devices */
  359         if (vp->v_type != VCHR && count > LLONG_MAX - offset) {
  360                 error = EINVAL;
  361                 goto done;
  362         }
  363 
  364         if (vp->v_type == VDIR) {
  365                 error = EISDIR;
  366                 goto done;
  367         }
  368 
  369         error = VOP_READ(vp, uio, (fp->f_flag & FNONBLOCK) ? IO_NDELAY : 0,
  370             cred);
  371         if ((fflags & FO_POSITION) == 0) {
  372                 mtx_enter(&fp->f_mtx);
  373                 fp->f_offset += count - uio->uio_resid;
  374                 mtx_leave(&fp->f_mtx);
  375         }
  376 done:
  377         VOP_UNLOCK(vp);
  378         KERNEL_UNLOCK();
  379         return (error);
  380 }
  381 
  382 /*
  383  * File table vnode write routine.
  384  */
  385 int
  386 vn_write(struct file *fp, struct uio *uio, int fflags)
  387 {
  388         struct vnode *vp = fp->f_data;
  389         struct ucred *cred = fp->f_cred;
  390         int error, ioflag = IO_UNIT;
  391         size_t count;
  392 
  393         KERNEL_LOCK();
  394 
  395         /* note: pwrite/pwritev are unaffected by O_APPEND */
  396         if (vp->v_type == VREG && (fp->f_flag & O_APPEND) &&
  397             (fflags & FO_POSITION) == 0)
  398                 ioflag |= IO_APPEND;
  399         if (fp->f_flag & FNONBLOCK)
  400                 ioflag |= IO_NDELAY;
  401         if ((fp->f_flag & FFSYNC) ||
  402             (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS)))
  403                 ioflag |= IO_SYNC;
  404         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  405         if ((fflags & FO_POSITION) == 0)
  406                 uio->uio_offset = fp->f_offset;
  407         count = uio->uio_resid;
  408         error = VOP_WRITE(vp, uio, ioflag, cred);
  409         if ((fflags & FO_POSITION) == 0) {
  410                 mtx_enter(&fp->f_mtx);
  411                 if (ioflag & IO_APPEND)
  412                         fp->f_offset = uio->uio_offset;
  413                 else
  414                         fp->f_offset += count - uio->uio_resid;
  415                 mtx_leave(&fp->f_mtx);
  416         }
  417         VOP_UNLOCK(vp);
  418 
  419         KERNEL_UNLOCK();
  420         return (error);
  421 }
  422 
  423 /*
  424  * File table wrapper for vn_stat
  425  */
  426 int
  427 vn_statfile(struct file *fp, struct stat *sb, struct proc *p)
  428 {
  429         struct vnode *vp = fp->f_data;
  430         return vn_stat(vp, sb, p);
  431 }
  432 
  433 /*
  434  * vnode stat routine.
  435  */
  436 int
  437 vn_stat(struct vnode *vp, struct stat *sb, struct proc *p)
  438 {
  439         struct vattr va;
  440         int error;
  441         mode_t mode;
  442 
  443         error = VOP_GETATTR(vp, &va, p->p_ucred, p);
  444         if (error)
  445                 return (error);
  446         /*
  447          * Copy from vattr table
  448          */
  449         memset(sb, 0, sizeof(*sb));
  450         sb->st_dev = va.va_fsid;
  451         sb->st_ino = va.va_fileid;
  452         mode = va.va_mode;
  453         switch (vp->v_type) {
  454         case VREG:
  455                 mode |= S_IFREG;
  456                 break;
  457         case VDIR:
  458                 mode |= S_IFDIR;
  459                 break;
  460         case VBLK:
  461                 mode |= S_IFBLK;
  462                 break;
  463         case VCHR:
  464                 mode |= S_IFCHR;
  465                 break;
  466         case VLNK:
  467                 mode |= S_IFLNK;
  468                 break;
  469         case VSOCK:
  470                 mode |= S_IFSOCK;
  471                 break;
  472         case VFIFO:
  473                 mode |= S_IFIFO;
  474                 break;
  475         default:
  476                 return (EBADF);
  477         }
  478         sb->st_mode = mode;
  479         sb->st_nlink = va.va_nlink;
  480         sb->st_uid = va.va_uid;
  481         sb->st_gid = va.va_gid;
  482         sb->st_rdev = va.va_rdev;
  483         sb->st_size = va.va_size;
  484         sb->st_atim.tv_sec  = va.va_atime.tv_sec;
  485         sb->st_atim.tv_nsec = va.va_atime.tv_nsec;
  486         sb->st_mtim.tv_sec  = va.va_mtime.tv_sec;
  487         sb->st_mtim.tv_nsec = va.va_mtime.tv_nsec;
  488         sb->st_ctim.tv_sec  = va.va_ctime.tv_sec;
  489         sb->st_ctim.tv_nsec = va.va_ctime.tv_nsec;
  490         sb->st_blksize = va.va_blocksize;
  491         sb->st_flags = va.va_flags;
  492         sb->st_gen = va.va_gen;
  493         sb->st_blocks = va.va_bytes / S_BLKSIZE;
  494         return (0);
  495 }
  496 
  497 /*
  498  * File table vnode ioctl routine.
  499  */
  500 int
  501 vn_ioctl(struct file *fp, u_long com, caddr_t data, struct proc *p)
  502 {
  503         struct vnode *vp = fp->f_data;
  504         struct vattr vattr;
  505         int error = ENOTTY;
  506 
  507         KERNEL_LOCK();
  508         switch (vp->v_type) {
  509 
  510         case VREG:
  511         case VDIR:
  512                 if (com == FIONREAD) {
  513                         error = VOP_GETATTR(vp, &vattr, p->p_ucred, p);
  514                         if (error)
  515                                 break;
  516                         *(int *)data = vattr.va_size - foffset(fp);
  517 
  518                 } else if (com == FIONBIO || com == FIOASYNC)   /* XXX */
  519                         error = 0;                              /* XXX */
  520                 break;
  521 
  522         case VFIFO:
  523         case VCHR:
  524         case VBLK:
  525                 error = VOP_IOCTL(vp, com, data, fp->f_flag, p->p_ucred, p);
  526                 if (error == 0 && com == TIOCSCTTY) {
  527                         struct session *s = p->p_p->ps_session;
  528                         struct vnode *ovp = s->s_ttyvp;
  529                         s->s_ttyvp = vp;
  530                         vref(vp);
  531                         if (ovp)
  532                                 vrele(ovp);
  533                 }
  534                 break;
  535 
  536         default:
  537                 break;
  538         }
  539         KERNEL_UNLOCK();
  540 
  541         return (error);
  542 }
  543 
  544 /*
  545  * Check that the vnode is still valid, and if so
  546  * acquire requested lock.
  547  */
  548 int
  549 vn_lock(struct vnode *vp, int flags)
  550 {
  551         int error, xlocked, do_wakeup;
  552 
  553         do {
  554                 mtx_enter(&vnode_mtx);
  555                 if (vp->v_lflag & VXLOCK) {
  556                         vp->v_lflag |= VXWANT;
  557                         msleep_nsec(vp, &vnode_mtx, PINOD, "vn_lock", INFSLP);
  558                         mtx_leave(&vnode_mtx);
  559                         error = ENOENT;
  560                 } else {
  561                         vp->v_lockcount++;
  562                         mtx_leave(&vnode_mtx);
  563 
  564                         error = VOP_LOCK(vp, flags);
  565 
  566                         mtx_enter(&vnode_mtx);
  567                         vp->v_lockcount--;
  568                         do_wakeup = (vp->v_lockcount == 0);
  569                         xlocked = vp->v_lflag & VXLOCK;
  570                         mtx_leave(&vnode_mtx);
  571 
  572                         if (error == 0) {
  573                                 if (!xlocked)
  574                                         return (0);
  575 
  576                                 /*
  577                                  * The vnode was exclusively locked while
  578                                  * acquiring the requested lock. Release it and
  579                                  * try again.
  580                                  */
  581                                 error = ENOENT;
  582                                 VOP_UNLOCK(vp);
  583                                 if (do_wakeup)
  584                                         wakeup_one(&vp->v_lockcount);
  585                         }
  586                 }
  587         } while (flags & LK_RETRY);
  588         return (error);
  589 }
  590 
  591 /*
  592  * File table vnode close routine.
  593  */
  594 int
  595 vn_closefile(struct file *fp, struct proc *p)
  596 {
  597         struct vnode *vp = fp->f_data;
  598         struct flock lf;
  599         int error;
  600 
  601         KERNEL_LOCK();
  602         if ((fp->f_iflags & FIF_HASLOCK)) {
  603                 lf.l_whence = SEEK_SET;
  604                 lf.l_start = 0;
  605                 lf.l_len = 0;
  606                 lf.l_type = F_UNLCK;
  607                 (void) VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
  608         }
  609         error = vn_close(vp, fp->f_flag, fp->f_cred, p);
  610         KERNEL_UNLOCK();
  611         return (error);
  612 }
  613 
  614 int
  615 vn_kqfilter(struct file *fp, struct knote *kn)
  616 {
  617         int error;
  618 
  619         KERNEL_LOCK();
  620         error = VOP_KQFILTER(fp->f_data, fp->f_flag, kn);
  621         KERNEL_UNLOCK();
  622         return (error);
  623 }
  624 
  625 int
  626 vn_seek(struct file *fp, off_t *offset, int whence, struct proc *p)
  627 {
  628         struct ucred *cred = p->p_ucred;
  629         struct vnode *vp = fp->f_data;
  630         struct vattr vattr;
  631         off_t newoff;
  632         int error = 0;
  633         int special;
  634 
  635         if (vp->v_type == VFIFO)
  636                 return (ESPIPE);
  637 
  638         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  639 
  640         if (vp->v_type == VCHR)
  641                 special = 1;
  642         else
  643                 special = 0;
  644 
  645         switch (whence) {
  646         case SEEK_CUR:
  647                 newoff = fp->f_offset + *offset;
  648                 break;
  649         case SEEK_END:
  650                 KERNEL_LOCK();
  651                 error = VOP_GETATTR(vp, &vattr, cred, p);
  652                 KERNEL_UNLOCK();
  653                 if (error)
  654                         goto out;
  655                 newoff = *offset + (off_t)vattr.va_size;
  656                 break;
  657         case SEEK_SET:
  658                 newoff = *offset;
  659                 break;
  660         default:
  661                 error = EINVAL;
  662                 goto out;
  663         }
  664         if (!special && newoff < 0) {
  665                 error = EINVAL;
  666                 goto out;
  667         }
  668         mtx_enter(&fp->f_mtx);
  669         fp->f_offset = newoff;
  670         mtx_leave(&fp->f_mtx);
  671         *offset = newoff;
  672 
  673 out:
  674         VOP_UNLOCK(vp);
  675         return (error);
  676 }
  677 
  678 /*
  679  * Common code for vnode access operations.
  680  */
  681 
  682 /* Check if a directory can be found inside another in the hierarchy */
  683 int
  684 vn_isunder(struct vnode *lvp, struct vnode *rvp, struct proc *p)
  685 {
  686         int error;
  687 
  688         error = vfs_getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN/2, 0, p);
  689 
  690         if (!error)
  691                 return (1);
  692 
  693         return (0);
  694 }

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