freebsd-dev/sys/fs/fifofs/fifo_vnops.c
John Baldwin b501cc5da6 Rework pathconf handling for FIFOs.
On the one hand, FIFOs should respect other variables not supported by
the fifofs vnode operation (such as _PC_NAME_MAX, _PC_LINK_MAX, etc.).
These values are fs-specific and must come from a fs-specific method.
On the other hand, filesystems that support FIFOs are required to
support _PC_PIPE_BUF on directory vnodes that can contain FIFOs.
Given this latter requirement, once the fs-specific VOP_PATHCONF
method supports _PC_PIPE_BUF for directories, it is also suitable for
FIFOs permitting a single VOP_PATHCONF method to be used for both
FIFOs and non-FIFOs.

To that end, retire all of the FIFO-specific pathconf methods from
filesystems and change FIFO-specific vnode operation switches to use
the existing fs-specific VOP_PATHCONF method.  For fifofs, set it's
VOP_PATHCONF to VOP_PANIC since it should no longer be used.

While here, move _PC_PIPE_BUF handling out of vop_stdpathconf() so that
only filesystems supporting FIFOs will report a value.  In addition,
only report a valid _PC_PIPE_BUF for directories and FIFOs.

Discussed with:	bde
Reviewed by:	kib (part of a larger patch)
MFC after:	1 month
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D12572
2017-12-19 22:39:05 +00:00

361 lines
9.0 KiB
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,
};
/*
* 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) {
pipe_named_ctor(&fpipe, td);
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);
}
fp->f_seqcount = 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);
}
}
if ((ap->a_mode & O_NONBLOCK) == 0) {
if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
gen = fip->fi_wgen;
VOP_UNLOCK(vp, 0);
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);
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, 0);
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++;
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);
}