FreeBSD/Linux Kernel Cross Reference
sys/fs/fifofs/fifo_vnops.c

     /*-
      * Copyright (c) 1990, 1993, 1995
      *      The Regents of the University of California.
      * Copyright (c) 2005 Robert N. M. Watson
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)fifo_vnops.c        8.10 (Berkeley) 5/27/95
     * $FreeBSD: releng/9.2/sys/fs/fifofs/fifo_vnops.c 229245 2012-01-01 23:46:08Z kib $
     */
    
    #include <sys/param.h>
    #include <sys/event.h>
    #include <sys/file.h>
    #include <sys/filedesc.h>
    #include <sys/filio.h>
    #include <sys/fcntl.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/malloc.h>
    #include <sys/poll.h>
    #include <sys/proc.h>
    #include <sys/signalvar.h>
    #include <sys/socket.h>
    #include <sys/socketvar.h>
    #include <sys/sx.h>
    #include <sys/systm.h>
    #include <sys/un.h>
    #include <sys/unistd.h>
    #include <sys/vnode.h>
    #include <fs/fifofs/fifo.h>
    
    static fo_rdwr_t        fifo_read_f;
    static fo_rdwr_t        fifo_write_f;
    static fo_ioctl_t       fifo_ioctl_f;
    static fo_poll_t        fifo_poll_f;
    static fo_kqfilter_t    fifo_kqfilter_f;
    static fo_stat_t        fifo_stat_f;
    static fo_close_t       fifo_close_f;
    static fo_truncate_t    fifo_truncate_f;
    
    struct fileops fifo_ops_f = {
            .fo_read =      fifo_read_f,
            .fo_write =     fifo_write_f,
            .fo_truncate =  fifo_truncate_f,
            .fo_ioctl =     fifo_ioctl_f,
            .fo_poll =      fifo_poll_f,
            .fo_kqfilter =  fifo_kqfilter_f,
            .fo_stat =      fifo_stat_f,
            .fo_close =     fifo_close_f,
            .fo_chmod =     vn_chmod,
            .fo_chown =     vn_chown,
            .fo_flags =     DFLAG_PASSABLE
    };
    
    /*
     * This structure is associated with the FIFO vnode and stores
     * the state associated with the FIFO.
     * Notes about locking:
     *   - fi_readsock and fi_writesock are invariant since init time.
     *   - fi_readers and fi_writers are vnode lock protected.
     *   - fi_wgen is fif_mtx lock protected.
     */
    struct fifoinfo {
            struct socket   *fi_readsock;
            struct socket   *fi_writesock;
            long            fi_readers;
            long            fi_writers;
            int             fi_wgen;
    };
    
    static vop_print_t      fifo_print;
    static vop_open_t       fifo_open;
    static vop_close_t      fifo_close;
    static vop_pathconf_t   fifo_pathconf;
   static vop_advlock_t    fifo_advlock;
   
   static void     filt_fifordetach(struct knote *kn);
   static int      filt_fiforead(struct knote *kn, long hint);
   static void     filt_fifowdetach(struct knote *kn);
   static int      filt_fifowrite(struct knote *kn, long hint);
   static void     filt_fifodetach_notsup(struct knote *kn);
   static int      filt_fifo_notsup(struct knote *kn, long hint);
   
   static struct filterops fiforead_filtops = {
           .f_isfd = 1,
           .f_detach = filt_fifordetach,
           .f_event = filt_fiforead,
   };
   static struct filterops fifowrite_filtops = {
           .f_isfd = 1,
           .f_detach = filt_fifowdetach,
           .f_event = filt_fifowrite,
   };
   static struct filterops fifo_notsup_filtops = {
           .f_isfd = 1,
           .f_detach = filt_fifodetach_notsup,
           .f_event = filt_fifo_notsup,
   };
   
   struct vop_vector fifo_specops = {
           .vop_default =          &default_vnodeops,
   
           .vop_advlock =          fifo_advlock,
           .vop_close =            fifo_close,
           .vop_create =           VOP_PANIC,
           .vop_getattr =          VOP_EBADF,
           .vop_ioctl =            VOP_PANIC,
           .vop_kqfilter =         VOP_PANIC,
           .vop_link =             VOP_PANIC,
           .vop_mkdir =            VOP_PANIC,
           .vop_mknod =            VOP_PANIC,
           .vop_open =             fifo_open,
           .vop_pathconf =         fifo_pathconf,
           .vop_print =            fifo_print,
           .vop_read =             VOP_PANIC,
           .vop_readdir =          VOP_PANIC,
           .vop_readlink =         VOP_PANIC,
           .vop_reallocblks =      VOP_PANIC,
           .vop_reclaim =          VOP_NULL,
           .vop_remove =           VOP_PANIC,
           .vop_rename =           VOP_PANIC,
           .vop_rmdir =            VOP_PANIC,
           .vop_setattr =          VOP_EBADF,
           .vop_symlink =          VOP_PANIC,
           .vop_write =            VOP_PANIC,
   };
   
   struct mtx fifo_mtx;
   MTX_SYSINIT(fifo, &fifo_mtx, "fifo mutex", MTX_DEF);
   
   /*
    * Dispose of fifo resources.
    */
   static void
   fifo_cleanup(struct vnode *vp)
   {
           struct fifoinfo *fip = vp->v_fifoinfo;
   
           ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
           if (fip->fi_readers == 0 && fip->fi_writers == 0) {
                   vp->v_fifoinfo = NULL;
                   (void)soclose(fip->fi_readsock);
                   (void)soclose(fip->fi_writesock);
                   free(fip, M_VNODE);
           }
   }
   
   /*
    * Open called to set up a new instance of a fifo or
    * to find an active instance of a fifo.
    */
   /* ARGSUSED */
   static int
   fifo_open(ap)
           struct vop_open_args /* {
                   struct vnode *a_vp;
                   int  a_mode;
                   struct ucred *a_cred;
                   struct thread *a_td;
                   struct file *a_fp;
           } */ *ap;
   {
           struct vnode *vp = ap->a_vp;
           struct fifoinfo *fip;
           struct thread *td = ap->a_td;
           struct ucred *cred = ap->a_cred;
           struct file *fp = ap->a_fp;
           struct socket *rso, *wso;
           int error;
   
           ASSERT_VOP_ELOCKED(vp, "fifo_open");
           if (fp == NULL)
                   return (EINVAL);
           if ((fip = vp->v_fifoinfo) == NULL) {
                   fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
                   error = socreate(AF_LOCAL, &rso, SOCK_STREAM, 0, cred, td);
                   if (error)
                           goto fail1;
                   fip->fi_readsock = rso;
                   error = socreate(AF_LOCAL, &wso, SOCK_STREAM, 0, cred, td);
                   if (error)
                           goto fail2;
                   fip->fi_writesock = wso;
                   error = soconnect2(wso, rso);
                   /* Close the direction we do not use, so we can get POLLHUP. */
                   if (error == 0)
                           error = soshutdown(rso, SHUT_WR);
                   if (error) {
                           (void)soclose(wso);
   fail2:
                           (void)soclose(rso);
   fail1:
                           free(fip, M_VNODE);
                           return (error);
                   }
                   fip->fi_wgen = fip->fi_readers = fip->fi_writers = 0;
                   wso->so_snd.sb_lowat = PIPE_BUF;
                   SOCKBUF_LOCK(&rso->so_rcv);
                   rso->so_rcv.sb_state |= SBS_CANTRCVMORE;
                   SOCKBUF_UNLOCK(&rso->so_rcv);
                   KASSERT(vp->v_fifoinfo == NULL,
                       ("fifo_open: v_fifoinfo race"));
                   vp->v_fifoinfo = fip;
           }
   
           /*
            * Use the fifo_mtx lock here, in addition to the vnode lock,
            * in order to allow vnode lock dropping before msleep() calls
            * and still avoiding missed wakeups.
            */
           mtx_lock(&fifo_mtx);
           if (ap->a_mode & FREAD) {
                   fip->fi_readers++;
                   if (fip->fi_readers == 1) {
                           SOCKBUF_LOCK(&fip->fi_writesock->so_snd);
                           fip->fi_writesock->so_snd.sb_state &= ~SBS_CANTSENDMORE;
                           SOCKBUF_UNLOCK(&fip->fi_writesock->so_snd);
                           if (fip->fi_writers > 0) {
                                   wakeup(&fip->fi_writers);
                                   sowwakeup(fip->fi_writesock);
                           }
                   }
                   fp->f_seqcount = fip->fi_wgen - fip->fi_writers;
           }
           if (ap->a_mode & FWRITE) {
                   if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
                           mtx_unlock(&fifo_mtx);
                           if (fip->fi_writers == 0)
                                   fifo_cleanup(vp);
                           return (ENXIO);
                   }
                   fip->fi_writers++;
                   if (fip->fi_writers == 1) {
                           SOCKBUF_LOCK(&fip->fi_readsock->so_rcv);
                           fip->fi_readsock->so_rcv.sb_state &= ~SBS_CANTRCVMORE;
                           SOCKBUF_UNLOCK(&fip->fi_readsock->so_rcv);
                           if (fip->fi_readers > 0) {
                                   wakeup(&fip->fi_readers);
                                   sorwakeup(fip->fi_readsock);
                           }
                   }
           }
           if ((ap->a_mode & O_NONBLOCK) == 0) {
                   if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
                           VOP_UNLOCK(vp, 0);
                           error = msleep(&fip->fi_readers, &fifo_mtx,
                               PDROP | PCATCH | PSOCK, "fifoor", 0);
                           vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                           if (error) {
                                   fip->fi_readers--;
                                   if (fip->fi_readers == 0) {
                                           socantsendmore(fip->fi_writesock);
                                           fifo_cleanup(vp);
                                   }
                                   return (error);
                           }
                           mtx_lock(&fifo_mtx);
                           /*
                            * We must have got woken up because we had a writer.
                            * That (and not still having one) is the condition
                            * that we must wait for.
                            */
                   }
                   if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
                           VOP_UNLOCK(vp, 0);
                           error = msleep(&fip->fi_writers, &fifo_mtx,
                               PDROP | PCATCH | PSOCK, "fifoow", 0);
                           vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                           if (error) {
                                   fip->fi_writers--;
                                   if (fip->fi_writers == 0) {
                                           socantrcvmore(fip->fi_readsock);
                                           mtx_lock(&fifo_mtx);
                                           fip->fi_wgen++;
                                           mtx_unlock(&fifo_mtx);
                                           fifo_cleanup(vp);
                                   }
                                   return (error);
                           }
                           /*
                            * We must have got woken up because we had
                            * a reader.  That (and not still having one)
                            * is the condition that we must wait for.
                            */
                           mtx_lock(&fifo_mtx);
                   }
           }
           mtx_unlock(&fifo_mtx);
           KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
           KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
           finit(fp, fp->f_flag, DTYPE_FIFO, fip, &fifo_ops_f);
           return (0);
   }
   
   static void
   filt_fifordetach(struct knote *kn)
   {
           struct socket *so = (struct socket *)kn->kn_hook;
   
           SOCKBUF_LOCK(&so->so_rcv);
           knlist_remove(&so->so_rcv.sb_sel.si_note, kn, 1);
           if (knlist_empty(&so->so_rcv.sb_sel.si_note))
                   so->so_rcv.sb_flags &= ~SB_KNOTE;
           SOCKBUF_UNLOCK(&so->so_rcv);
   }
   
   static int
   filt_fiforead(struct knote *kn, long hint)
   {
           struct socket *so = (struct socket *)kn->kn_hook;
   
           SOCKBUF_LOCK_ASSERT(&so->so_rcv);
           kn->kn_data = so->so_rcv.sb_cc;
           if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
                   kn->kn_flags |= EV_EOF;
                   return (1);
           } else {
                   kn->kn_flags &= ~EV_EOF;
                   return (kn->kn_data > 0);
           }
   }
   
   static void
   filt_fifowdetach(struct knote *kn)
   {
           struct socket *so = (struct socket *)kn->kn_hook;
   
           SOCKBUF_LOCK(&so->so_snd);
           knlist_remove(&so->so_snd.sb_sel.si_note, kn, 1);
           if (knlist_empty(&so->so_snd.sb_sel.si_note))
                   so->so_snd.sb_flags &= ~SB_KNOTE;
           SOCKBUF_UNLOCK(&so->so_snd);
   }
   
   static int
   filt_fifowrite(struct knote *kn, long hint)
   {
           struct socket *so = (struct socket *)kn->kn_hook;
   
           SOCKBUF_LOCK_ASSERT(&so->so_snd);
           kn->kn_data = sbspace(&so->so_snd);
           if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                   kn->kn_flags |= EV_EOF;
                   return (1);
           } else {
                   kn->kn_flags &= ~EV_EOF;
                   return (kn->kn_data >= so->so_snd.sb_lowat);
           }
   }
   
   static void
   filt_fifodetach_notsup(struct knote *kn)
   {
   
   }
   
   static int
   filt_fifo_notsup(struct knote *kn, long hint)
   {
   
           return (0);
   }
   
   /*
    * Device close routine
    */
   /* ARGSUSED */
   static int
   fifo_close(ap)
           struct vop_close_args /* {
                   struct vnode *a_vp;
                   int  a_fflag;
                   struct ucred *a_cred;
                   struct thread *a_td;
           } */ *ap;
   {
           struct vnode *vp = ap->a_vp;
           struct fifoinfo *fip = vp->v_fifoinfo;
   
           ASSERT_VOP_ELOCKED(vp, "fifo_close");
           if (fip == NULL) {
                   printf("fifo_close: no v_fifoinfo %p\n", vp);
                   return (0);
           }
           if (ap->a_fflag & FREAD) {
                   fip->fi_readers--;
                   if (fip->fi_readers == 0)
                           socantsendmore(fip->fi_writesock);
           }
           if (ap->a_fflag & FWRITE) {
                   fip->fi_writers--;
                   if (fip->fi_writers == 0) {
                           socantrcvmore(fip->fi_readsock);
                           mtx_lock(&fifo_mtx);
                           fip->fi_wgen++;
                           mtx_unlock(&fifo_mtx);
                   }
           }
           fifo_cleanup(vp);
           return (0);
   }
   
   /*
    * Print out internal contents of a fifo vnode.
    */
   int
   fifo_printinfo(vp)
           struct vnode *vp;
   {
           register struct fifoinfo *fip = vp->v_fifoinfo;
   
           if (fip == NULL){
                   printf(", NULL v_fifoinfo");
                   return (0);
           }
           printf(", fifo with %ld readers and %ld writers",
                   fip->fi_readers, fip->fi_writers);
           return (0);
   }
   
   /*
    * Print out the contents of a fifo vnode.
    */
   static int
   fifo_print(ap)
           struct vop_print_args /* {
                   struct vnode *a_vp;
           } */ *ap;
   {
           printf("    ");
           fifo_printinfo(ap->a_vp);
           printf("\n");
           return (0);
   }
   
   /*
    * Return POSIX pathconf information applicable to fifo's.
    */
   static int
   fifo_pathconf(ap)
           struct vop_pathconf_args /* {
                   struct vnode *a_vp;
                   int a_name;
                   int *a_retval;
           } */ *ap;
   {
   
           switch (ap->a_name) {
           case _PC_LINK_MAX:
                   *ap->a_retval = LINK_MAX;
                   return (0);
           case _PC_PIPE_BUF:
                   *ap->a_retval = PIPE_BUF;
                   return (0);
           case _PC_CHOWN_RESTRICTED:
                   *ap->a_retval = 1;
                   return (0);
           default:
                   return (EINVAL);
           }
           /* NOTREACHED */
   }
   
   /*
    * Fifo advisory byte-level locks.
    */
   /* ARGSUSED */
   static int
   fifo_advlock(ap)
           struct vop_advlock_args /* {
                   struct vnode *a_vp;
                   caddr_t  a_id;
                   int  a_op;
                   struct flock *a_fl;
                   int  a_flags;
           } */ *ap;
   {
   
           return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
   }
   
   static int
   fifo_close_f(struct file *fp, struct thread *td)
   {
   
           return (vnops.fo_close(fp, td));
   }
   
   /*
    * The implementation of ioctl() for named fifos is complicated by the fact
    * that we permit O_RDWR fifo file descriptors, meaning that the actions of
    * ioctls may have to be applied to both the underlying sockets rather than
    * just one.  The original implementation simply forward the ioctl to one
    * or both sockets based on fp->f_flag.  We now consider each ioctl
    * separately, as the composition effect requires careful ordering.
    *
    * We do not blindly pass all ioctls through to the socket in order to avoid
    * providing unnecessary ioctls that might be improperly depended on by
    * applications (such as socket-specific, routing, and interface ioctls).
    *
    * Unlike sys_pipe.c, fifos do not implement the deprecated TIOCSPGRP and
    * TIOCGPGRP ioctls.  Earlier implementations of fifos did forward SIOCSPGRP
    * and SIOCGPGRP ioctls, so we might need to re-add those here.
    */
   static int
   fifo_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred,
       struct thread *td)
   {
           struct fifoinfo *fi;
           struct file filetmp;    /* Local, so need not be locked. */
           int error;
   
           error = ENOTTY;
           fi = fp->f_data;
   
           switch (com) {
           case FIONBIO:
                   /*
                    * Non-blocking I/O is implemented at the fifo layer using
                    * MSG_NBIO, so does not need to be forwarded down the stack.
                    */
                   return (0);
   
           case FIOASYNC:
           case FIOSETOWN:
           case FIOGETOWN:
                   /*
                    * These socket ioctls don't have any ordering requirements,
                    * so are called in an arbitrary order, and only on the
                    * sockets indicated by the file descriptor rights.
                    *
                    * XXXRW: If O_RDWR and the read socket accepts an ioctl but
                    * the write socket doesn't, the socketpair is left in an
                    * inconsistent state.
                    */
                   if (fp->f_flag & FREAD) {
                           filetmp.f_data = fi->fi_readsock;
                           filetmp.f_cred = cred;
                           error = soo_ioctl(&filetmp, com, data, cred, td);
                           if (error)
                                   return (error);
                   }
                   if (fp->f_flag & FWRITE) {
                           filetmp.f_data = fi->fi_writesock;
                           filetmp.f_cred = cred;
                           error = soo_ioctl(&filetmp, com, data, cred, td);
                   }
                   return (error);
   
           case FIONREAD:
                   /*
                    * FIONREAD will return 0 for non-readable descriptors, and
                    * the results of FIONREAD on the read socket for readable
                    * descriptors.
                    */
                   if (!(fp->f_flag & FREAD)) {
                           *(int *)data = 0;
                           return (0);
                   }
                   filetmp.f_data = fi->fi_readsock;
                   filetmp.f_cred = cred;
                   return (soo_ioctl(&filetmp, com, data, cred, td));
   
           default:
                   return (ENOTTY);
           }
   }
   
   /*
    * Because fifos are now a file descriptor layer object, EVFILT_VNODE is not
    * implemented.  Likely, fifo_kqfilter() should be removed, and
    * fifo_kqfilter_f() should know how to forward the request to the underling
    * vnode using f_vnode in the file descriptor here.
    */
   static int
   fifo_kqfilter_f(struct file *fp, struct knote *kn)
   {
           struct fifoinfo *fi;
           struct socket *so;
           struct sockbuf *sb;
   
           fi = fp->f_data;
   
           /*
            * If a filter is requested that is not supported by this file
            * descriptor, don't return an error, but also don't ever generate an
            * event.
            */
           if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
                   kn->kn_fop = &fifo_notsup_filtops;
                   return (0);
           }
   
           if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
                   kn->kn_fop = &fifo_notsup_filtops;
                   return (0);
           }
   
           switch (kn->kn_filter) {
           case EVFILT_READ:
                   kn->kn_fop = &fiforead_filtops;
                   so = fi->fi_readsock;
                   sb = &so->so_rcv;
                   break;
           case EVFILT_WRITE:
                   kn->kn_fop = &fifowrite_filtops;
                   so = fi->fi_writesock;
                   sb = &so->so_snd;
                   break;
           default:
                   return (EINVAL);
           }
   
           kn->kn_hook = (caddr_t)so;
   
           SOCKBUF_LOCK(sb);
           knlist_add(&sb->sb_sel.si_note, kn, 1);
           sb->sb_flags |= SB_KNOTE;
           SOCKBUF_UNLOCK(sb);
   
           return (0);
   }
   
   static int
   fifo_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
   {
           struct fifoinfo *fip;
           struct file filetmp;
           int levents, revents = 0;
   
           fip = fp->f_data;
           levents = events &
               (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
           if ((fp->f_flag & FREAD) && levents) {
                   filetmp.f_data = fip->fi_readsock;
                   filetmp.f_cred = cred;
                   mtx_lock(&fifo_mtx);
                   if (fp->f_seqcount == fip->fi_wgen)
                           levents |= POLLINIGNEOF;
                   mtx_unlock(&fifo_mtx);
                   revents |= soo_poll(&filetmp, levents, cred, td);
           }
           levents = events & (POLLOUT | POLLWRNORM | POLLWRBAND);
           if ((fp->f_flag & FWRITE) && levents) {
                   filetmp.f_data = fip->fi_writesock;
                   filetmp.f_cred = cred;
                   revents |= soo_poll(&filetmp, levents, cred, td);
           }
           return (revents);
   }
   
   static int
   fifo_read_f(struct file *fp, struct uio *uio, struct ucred *cred, int flags, struct thread *td)
   {
           struct fifoinfo *fip;
           int sflags;
   
           fip = fp->f_data;
           KASSERT(uio->uio_rw == UIO_READ,("fifo_read mode"));
           if (uio->uio_resid == 0)
                   return (0);
           sflags = (fp->f_flag & FNONBLOCK) ? MSG_NBIO : 0;
           return (soreceive(fip->fi_readsock, NULL, uio, NULL, NULL, &sflags));
   }
   
   static int
   fifo_stat_f(struct file *fp, struct stat *sb, struct ucred *cred, struct thread *td)
   {
   
           return (vnops.fo_stat(fp, sb, cred, td));
   }
   
   static int
   fifo_truncate_f(struct file *fp, off_t length, struct ucred *cred, struct thread *td)
   {
   
           return (vnops.fo_truncate(fp, length, cred, td));
   }
   
   static int
   fifo_write_f(struct file *fp, struct uio *uio, struct ucred *cred, int flags, struct thread *td)
   {
           struct fifoinfo *fip;
           int sflags;
   
           fip = fp->f_data;
           KASSERT(uio->uio_rw == UIO_WRITE,("fifo_write mode"));
           sflags = (fp->f_flag & FNONBLOCK) ? MSG_NBIO : 0;
           return (sosend(fip->fi_writesock, NULL, uio, 0, NULL, sflags, td));
   }

Cache object: 95cf2f222c91ebe2e6a14a423515a7a2