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fifo_vnops.c
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Editing: fifo_vnops.c
/*- * SPDX-License-Identifier: BSD-3-Clause * * Copyright (c) 1990, 1993, 1995 * The Regents of the University of California. * Copyright (c) 2005 Robert N. M. Watson * Copyright (c) 2012 Giovanni Trematerra * 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. * 3. 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 * $FreeBSD$ */ #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/selinfo.h> #include <sys/pipe.h> #include <sys/proc.h> #include <sys/signalvar.h> #include <sys/sx.h> #include <sys/systm.h> #include <sys/un.h> #include <sys/unistd.h> #include <sys/vnode.h> /* * This structure is associated with the FIFO vnode and stores * the state associated with the FIFO. * Notes about locking: * - fi_pipe is invariant since init time. * - fi_readers and fi_writers are protected by the vnode lock. */ struct fifoinfo { struct pipe *fi_pipe; long fi_readers; long fi_writers; u_int fi_rgen; u_int fi_wgen; }; static vop_print_t fifo_print; static vop_open_t fifo_open; static vop_close_t fifo_close; static vop_advlock_t fifo_advlock; 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 = VOP_PANIC, .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, }; VFS_VOP_VECTOR_REGISTER(fifo_specops); /* * Dispose of fifo resources. */ static void fifo_cleanup(struct vnode *vp) { struct fifoinfo *fip; ASSERT_VOP_ELOCKED(vp, "fifo_cleanup"); fip = vp->v_fifoinfo; if (fip->fi_readers == 0 && fip->fi_writers == 0) { vp->v_fifoinfo = NULL; pipe_dtor(fip->fi_pipe); 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; struct file *fp; struct thread *td; struct fifoinfo *fip; struct pipe *fpipe; u_int gen; int error, stops_deferred; vp = ap->a_vp; fp = ap->a_fp; td = ap->a_td; ASSERT_VOP_ELOCKED(vp, "fifo_open"); if (fp == NULL || (ap->a_mode & FEXEC) != 0) return (EINVAL); if ((fip = vp->v_fifoinfo) == NULL) { error = pipe_named_ctor(&fpipe, td); if (error != 0) return (error); fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK); fip->fi_pipe = fpipe; fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0; KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race")); vp->v_fifoinfo = fip; } fpipe = fip->fi_pipe; KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL")); /* * Use the pipe mutex here, in addition to the vnode lock, * in order to allow vnode lock dropping before msleep() calls * and still avoiding missed wakeups. */ PIPE_LOCK(fpipe); if (ap->a_mode & FREAD) { fip->fi_readers++; fip->fi_rgen++; if (fip->fi_readers == 1) { fpipe->pipe_state &= ~PIPE_EOF; if (fip->fi_writers > 0) { wakeup(&fip->fi_writers); pipeselwakeup(fpipe); } } fp->f_pipegen = fpipe->pipe_wgen - fip->fi_writers; } if (ap->a_mode & FWRITE) { if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) { PIPE_UNLOCK(fpipe); if (fip->fi_writers == 0) fifo_cleanup(vp); return (ENXIO); } fip->fi_writers++; fip->fi_wgen++; if (fip->fi_writers == 1) { fpipe->pipe_state &= ~PIPE_EOF; if (fip->fi_readers > 0) { wakeup(&fip->fi_readers); pipeselwakeup(fpipe); } } } if ((ap->a_mode & O_NONBLOCK) == 0) { if ((ap->a_mode & FREAD) && fip->fi_writers == 0) { gen = fip->fi_wgen; VOP_UNLOCK(vp); stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); error = msleep(&fip->fi_readers, PIPE_MTX(fpipe), PDROP | PCATCH | PSOCK, "fifoor", 0); sigallowstop(stops_deferred); vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); if (error != 0 && gen == fip->fi_wgen) { fip->fi_readers--; if (fip->fi_readers == 0) { PIPE_LOCK(fpipe); fpipe->pipe_state |= PIPE_EOF; if (fpipe->pipe_state & PIPE_WANTW) wakeup(fpipe); pipeselwakeup(fpipe); PIPE_UNLOCK(fpipe); fifo_cleanup(vp); } return (error); } PIPE_LOCK(fpipe); /* * 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) { gen = fip->fi_rgen; VOP_UNLOCK(vp); stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); error = msleep(&fip->fi_writers, PIPE_MTX(fpipe), PDROP | PCATCH | PSOCK, "fifoow", 0); sigallowstop(stops_deferred); vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); if (error != 0 && gen == fip->fi_rgen) { fip->fi_writers--; if (fip->fi_writers == 0) { PIPE_LOCK(fpipe); fpipe->pipe_state |= PIPE_EOF; if (fpipe->pipe_state & PIPE_WANTR) wakeup(fpipe); fpipe->pipe_wgen++; pipeselwakeup(fpipe); PIPE_UNLOCK(fpipe); 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. */ PIPE_LOCK(fpipe); } } PIPE_UNLOCK(fpipe); 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, fpipe, &pipeops); 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; struct fifoinfo *fip; struct pipe *cpipe; vp = ap->a_vp; fip = vp->v_fifoinfo; cpipe = fip->fi_pipe; ASSERT_VOP_ELOCKED(vp, "fifo_close"); if (ap->a_fflag & FREAD) { fip->fi_readers--; if (fip->fi_readers == 0) { PIPE_LOCK(cpipe); cpipe->pipe_state |= PIPE_EOF; if ((cpipe->pipe_state & PIPE_WANTW)) { cpipe->pipe_state &= ~PIPE_WANTW; wakeup(cpipe); } pipeselwakeup(cpipe); PIPE_UNLOCK(cpipe); } } if (ap->a_fflag & FWRITE) { fip->fi_writers--; if (fip->fi_writers == 0) { PIPE_LOCK(cpipe); cpipe->pipe_state |= PIPE_EOF; if ((cpipe->pipe_state & PIPE_WANTR)) { cpipe->pipe_state &= ~PIPE_WANTR; wakeup(cpipe); } cpipe->pipe_wgen++; pipeselwakeup(cpipe); PIPE_UNLOCK(cpipe); } } fifo_cleanup(vp); return (0); } /* * Print out internal contents of a fifo vnode. */ int fifo_printinfo(vp) struct vnode *vp; { 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); } /* * 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); }
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