minix/servers/vfs/pipe.c
Lionel Sambuc 7031438f58 Message type and related cleanup
- Intorduce and use a message type for VFS_GETDENTS, VFS_READ,
   VFS_WRITE.

 - Some cleanup to related functions where vir_bytes are replaced (and
   casted to/from, in parameter definition and local variables as well.

   This allow to see more clearly which function receives unsafe
   (pointer) values, or at least values which are not supposed to be
   valid in the address space of VFS. The current patch does so only
   for the minimal amount of functions which are concerned with the
   introduction of the new message type.

Change-Id: I0cdca97409c4016d02fae067b48bf55d37572c5c
2014-07-28 17:05:34 +02:00

572 lines
16 KiB
C

/* This file deals with the suspension and revival of processes. A process can
* be suspended because it wants to read or write from a pipe and can't, or
* because it wants to read or write from a special file and can't. When a
* process can't continue it is suspended, and revived later when it is able
* to continue.
*
* The entry points into this file are
* do_pipe2: perform the PIPE2 system call
* pipe_check: check to see that a read or write on a pipe is feasible now
* suspend: suspend a process that cannot do a requested read or write
* release: check to see if a suspended process can be released and do
* it
* revive: mark a suspended process as able to run again
* unsuspend_by_endpt: revive all processes blocking on a given process
* do_unpause: a signal has been sent to a process; see if it suspended
*/
#include "fs.h"
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <assert.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <sys/select.h>
#include <sys/time.h>
#include "file.h"
#include "scratchpad.h"
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
static int create_pipe(int fil_des[2], int flags);
/*===========================================================================*
* do_pipe2 *
*===========================================================================*/
int do_pipe2(void)
{
/* Perform the pipe2(fil_des[2], flags) system call. */
int r, flags;
int fil_des[2]; /* reply goes here */
flags = job_m_in.m_lc_vfs_pipe2.flags;
r = create_pipe(fil_des, flags);
if (r == OK) {
job_m_out.m_lc_vfs_pipe2.fd0 = fil_des[0];
job_m_out.m_lc_vfs_pipe2.fd1 = fil_des[1];
}
return r;
}
/*===========================================================================*
* create_pipe *
*===========================================================================*/
static int create_pipe(int fil_des[2], int flags)
{
register struct fproc *rfp;
int r;
struct filp *fil_ptr0, *fil_ptr1;
struct vnode *vp;
struct vmnt *vmp;
struct node_details res;
/* Get a lock on PFS */
if ((vmp = find_vmnt(PFS_PROC_NR)) == NULL) panic("PFS gone");
if ((r = lock_vmnt(vmp, VMNT_READ)) != OK) return(r);
/* See if a free vnode is available */
if ((vp = get_free_vnode()) == NULL) {
unlock_vmnt(vmp);
return(err_code);
}
lock_vnode(vp, VNODE_OPCL);
/* Acquire two file descriptors. */
rfp = fp;
if ((r = get_fd(fp, 0, R_BIT, &fil_des[0], &fil_ptr0)) != OK) {
unlock_vnode(vp);
unlock_vmnt(vmp);
return(r);
}
rfp->fp_filp[fil_des[0]] = fil_ptr0;
fil_ptr0->filp_count = 1; /* mark filp in use */
if ((r = get_fd(fp, 0, W_BIT, &fil_des[1], &fil_ptr1)) != OK) {
rfp->fp_filp[fil_des[0]] = NULL;
fil_ptr0->filp_count = 0; /* mark filp free */
unlock_filp(fil_ptr0);
unlock_vnode(vp);
unlock_vmnt(vmp);
return(r);
}
rfp->fp_filp[fil_des[1]] = fil_ptr1;
fil_ptr1->filp_count = 1;
/* Create a named pipe inode on PipeFS */
r = req_newnode(PFS_PROC_NR, fp->fp_effuid, fp->fp_effgid, I_NAMED_PIPE,
NO_DEV, &res);
if (r != OK) {
rfp->fp_filp[fil_des[0]] = NULL;
fil_ptr0->filp_count = 0;
rfp->fp_filp[fil_des[1]] = NULL;
fil_ptr1->filp_count = 0;
unlock_filp(fil_ptr1);
unlock_filp(fil_ptr0);
unlock_vnode(vp);
unlock_vmnt(vmp);
return(r);
}
/* Fill in vnode */
vp->v_fs_e = res.fs_e;
vp->v_mapfs_e = res.fs_e;
vp->v_inode_nr = res.inode_nr;
vp->v_mapinode_nr = res.inode_nr;
vp->v_mode = res.fmode;
vp->v_fs_count = 1;
vp->v_mapfs_count = 1;
vp->v_ref_count = 1;
vp->v_size = 0;
vp->v_vmnt = NULL;
vp->v_dev = NO_DEV;
/* Fill in filp objects */
fil_ptr0->filp_vno = vp;
dup_vnode(vp);
fil_ptr1->filp_vno = vp;
fil_ptr0->filp_flags = O_RDONLY | (flags & ~O_ACCMODE);
fil_ptr1->filp_flags = O_WRONLY | (flags & ~O_ACCMODE);
if (flags & O_CLOEXEC) {
FD_SET(fil_des[0], &rfp->fp_cloexec_set);
FD_SET(fil_des[1], &rfp->fp_cloexec_set);
}
unlock_filps(fil_ptr0, fil_ptr1);
unlock_vmnt(vmp);
return(OK);
}
/*===========================================================================*
* map_vnode *
*===========================================================================*/
int map_vnode(vp, map_to_fs_e)
struct vnode *vp;
endpoint_t map_to_fs_e;
{
int r;
struct vmnt *vmp;
struct node_details res;
if(vp->v_mapfs_e != NONE) return(OK); /* Already mapped; nothing to do. */
if ((vmp = find_vmnt(map_to_fs_e)) == NULL)
panic("Can't map to unknown endpoint");
if ((r = lock_vmnt(vmp, VMNT_WRITE)) != OK) {
if (r == EBUSY)
vmp = NULL; /* Already locked, do not unlock */
else
return(r);
}
/* Create a temporary mapping of this inode to another FS. Read and write
* operations on data will be handled by that FS. The rest by the 'original'
* FS that holds the inode. */
if ((r = req_newnode(map_to_fs_e, fp->fp_effuid, fp->fp_effgid, I_NAMED_PIPE,
vp->v_dev, &res)) == OK) {
vp->v_mapfs_e = res.fs_e;
vp->v_mapinode_nr = res.inode_nr;
vp->v_mapfs_count = 1;
}
if (vmp) unlock_vmnt(vmp);
return(r);
}
/*===========================================================================*
* pipe_check *
*===========================================================================*/
int pipe_check(
struct filp *filp, /* the filp of the pipe */
int rw_flag, /* READING or WRITING */
int oflags, /* flags set by open or fcntl */
int bytes, /* bytes to be read or written (all chunks) */
int notouch /* check only */
)
{
/* Pipes are a little different. If a process reads from an empty pipe for
* which a writer still exists, suspend the reader. If the pipe is empty
* and there is no writer, return 0 bytes. If a process is writing to a
* pipe and no one is reading from it, give a broken pipe error.
*/
struct vnode *vp;
off_t pos;
int r = OK;
vp = filp->filp_vno;
/* Reads start at the beginning; writes append to pipes */
if (notouch) /* In this case we don't actually care whether data transfer
* would succeed. See POSIX 1003.1-2008 */
pos = 0;
else if (rw_flag == READING)
pos = 0;
else {
pos = vp->v_size;
}
/* If reading, check for empty pipe. */
if (rw_flag == READING) {
if (vp->v_size == 0) {
/* Process is reading from an empty pipe. */
if (find_filp(vp, W_BIT) != NULL) {
/* Writer exists */
if (oflags & O_NONBLOCK)
r = EAGAIN;
else
r = SUSPEND;
/* If need be, activate sleeping writers. */
/* We ignore notouch voluntary here. */
if (susp_count > 0)
release(vp, VFS_WRITE, susp_count);
}
return(r);
}
return(bytes);
}
/* Process is writing to a pipe. */
if (find_filp(vp, R_BIT) == NULL) {
return(EPIPE);
}
/* Calculate how many bytes can be written. */
if (pos + bytes > PIPE_BUF) {
if (oflags & O_NONBLOCK) {
if (bytes <= PIPE_BUF) {
/* Write has to be atomic */
return(EAGAIN);
}
/* Compute available space */
bytes = PIPE_BUF - pos;
if (bytes > 0) {
/* Do a partial write. Need to wakeup reader */
if (!notouch)
release(vp, VFS_READ, susp_count);
return(bytes);
} else {
/* Pipe is full */
return(EAGAIN);
}
}
if (bytes > PIPE_BUF) {
/* Compute available space */
bytes = PIPE_BUF - pos;
if (bytes > 0) {
/* Do a partial write. Need to wakeup reader
* since we'll suspend ourself in read_write()
*/
if (!notouch)
release(vp, VFS_READ, susp_count);
return(bytes);
}
}
/* Pipe is full */
return(SUSPEND);
}
/* Writing to an empty pipe. Search for suspended reader. */
if (pos == 0 && !notouch)
release(vp, VFS_READ, susp_count);
/* Requested amount fits */
return(bytes);
}
/*===========================================================================*
* suspend *
*===========================================================================*/
void suspend(int why)
{
/* Take measures to suspend the processing of the present system call.
* Store the parameters to be used upon resuming in the process table.
* (Actually they are not used when a process is waiting for an I/O device,
* but they are needed for pipes, and it is not worth making the distinction.)
* The SUSPEND pseudo error should be returned after calling suspend().
*/
if (why == FP_BLOCKED_ON_POPEN || why == FP_BLOCKED_ON_PIPE)
/* #procs susp'ed on pipe*/
susp_count++;
fp->fp_blocked_on = why;
assert(fp->fp_grant == GRANT_INVALID || !GRANT_VALID(fp->fp_grant));
fp->fp_block_callnr = job_call_nr;
}
/*===========================================================================*
* wait_for *
*===========================================================================*/
void wait_for(endpoint_t who)
{
if(who == NONE || who == ANY)
panic("suspend on NONE or ANY");
suspend(FP_BLOCKED_ON_OTHER);
fp->fp_task = who;
}
/*===========================================================================*
* pipe_suspend *
*===========================================================================*/
void pipe_suspend(filp, buf, size)
struct filp *filp;
vir_bytes buf;
size_t size;
{
/* Take measures to suspend the processing of the present system call.
* Store the parameters to be used upon resuming in the process table.
*/
scratch(fp).file.filp = filp;
scratch(fp).io.io_buffer = buf;
scratch(fp).io.io_nbytes = size;
suspend(FP_BLOCKED_ON_PIPE);
}
/*===========================================================================*
* unsuspend_by_endpt *
*===========================================================================*/
void unsuspend_by_endpt(endpoint_t proc_e)
{
/* Revive processes waiting for drivers (SUSPENDed) that have disappeared with
* return code EAGAIN.
*/
struct fproc *rp;
for (rp = &fproc[0]; rp < &fproc[NR_PROCS]; rp++) {
if (rp->fp_pid == PID_FREE) continue;
if (rp->fp_blocked_on == FP_BLOCKED_ON_OTHER && rp->fp_task == proc_e)
revive(rp->fp_endpoint, EIO);
}
/* Revive processes waiting in drivers on select()s with EAGAIN too */
select_unsuspend_by_endpt(proc_e);
return;
}
/*===========================================================================*
* release *
*===========================================================================*/
void release(vp, op, count)
register struct vnode *vp; /* inode of pipe */
int op; /* VFS_READ, VFS_WRITE, or VFS_OPEN */
int count; /* max number of processes to release */
{
/* Check to see if any process is hanging on vnode 'vp'. If one is, and it
* was trying to perform the call indicated by 'op', release it.
*/
register struct fproc *rp;
struct filp *f;
int selop;
/* Trying to perform the call also includes SELECTing on it with that
* operation.
*/
if (op == VFS_READ || op == VFS_WRITE) {
if (op == VFS_READ)
selop = SEL_RD;
else
selop = SEL_WR;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (f->filp_count < 1 || !(f->filp_pipe_select_ops & selop) ||
f->filp_vno != vp)
continue;
select_callback(f, selop);
f->filp_pipe_select_ops &= ~selop;
}
}
/* Search the proc table. */
for (rp = &fproc[0]; rp < &fproc[NR_PROCS] && count > 0; rp++) {
if (rp->fp_pid != PID_FREE && fp_is_blocked(rp) &&
!(rp->fp_flags & FP_REVIVED) && rp->fp_block_callnr == op) {
/* Find the vnode. Depending on the reason the process was
* suspended, there are different ways of finding it.
*/
if (rp->fp_blocked_on == FP_BLOCKED_ON_POPEN ||
rp->fp_blocked_on == FP_BLOCKED_ON_LOCK ||
rp->fp_blocked_on == FP_BLOCKED_ON_OTHER) {
f = rp->fp_filp[scratch(rp).file.fd_nr];
if (f == NULL || f->filp_mode == FILP_CLOSED)
continue;
if (rp->fp_filp[scratch(rp).file.fd_nr]->filp_vno != vp)
continue;
} else if (rp->fp_blocked_on == FP_BLOCKED_ON_PIPE) {
if (scratch(rp).file.filp == NULL)
continue;
if (scratch(rp).file.filp->filp_vno != vp)
continue;
} else
continue;
/* We found the vnode. Revive process. */
revive(rp->fp_endpoint, 0);
susp_count--; /* keep track of who is suspended */
if(susp_count < 0)
panic("susp_count now negative: %d", susp_count);
if (--count == 0) return;
}
}
}
/*===========================================================================*
* revive *
*===========================================================================*/
void revive(endpoint_t proc_e, int returned)
{
/* Revive a previously blocked process. When a process hangs on tty, this
* is the way it is eventually released. For processes blocked on _SELECT and
* _OTHER, this function MUST NOT block its calling thread.
*/
struct fproc *rfp;
int blocked_on;
int fd_nr, slot;
if (proc_e == NONE || isokendpt(proc_e, &slot) != OK) return;
rfp = &fproc[slot];
if (!fp_is_blocked(rfp) || (rfp->fp_flags & FP_REVIVED)) return;
/* The 'reviving' flag only applies to pipes. Processes waiting for TTY get
* a message right away. The revival process is different for TTY and pipes.
* For select and TTY revival, the work is already done, for pipes it is not:
* the proc must be restarted so it can try again.
*/
blocked_on = rfp->fp_blocked_on;
fd_nr = scratch(rfp).file.fd_nr;
if (blocked_on == FP_BLOCKED_ON_PIPE || blocked_on == FP_BLOCKED_ON_LOCK) {
/* Revive a process suspended on a pipe or lock. */
rfp->fp_flags |= FP_REVIVED;
reviving++; /* process was waiting on pipe or lock */
} else {
rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
scratch(rfp).file.fd_nr = 0;
if (blocked_on == FP_BLOCKED_ON_POPEN) {
/* process blocked in open or create */
replycode(proc_e, fd_nr);
} else if (blocked_on == FP_BLOCKED_ON_SELECT) {
replycode(proc_e, returned);
} else {
/* Revive a process suspended on TTY or other device.
* Pretend it wants only what there is.
*/
scratch(rfp).io.io_nbytes = returned;
/* If a grant has been issued by FS for this I/O, revoke
* it again now that I/O is done.
*/
if (GRANT_VALID(rfp->fp_grant)) {
if(cpf_revoke(rfp->fp_grant)) {
panic("VFS: revoke failed for grant: %d",
rfp->fp_grant);
}
rfp->fp_grant = GRANT_INVALID;
}
replycode(proc_e, returned);/* unblock the process */
}
}
}
/*===========================================================================*
* unpause *
*===========================================================================*/
void unpause(void)
{
/* A signal has been sent to a user who is paused on the file system.
* Abort the system call with the EINTR error message.
*/
int blocked_on, fild, status = EINTR;
struct filp *f;
dev_t dev;
int wasreviving = 0;
if (!fp_is_blocked(fp)) return;
blocked_on = fp->fp_blocked_on;
/* Clear the block status now. The procedure below might make blocking calls
* and it is imperative that while at least cdev_cancel() is executing, other
* parts of VFS do not perceive this process as blocked on something.
*/
fp->fp_blocked_on = FP_BLOCKED_ON_NONE;
if (fp->fp_flags & FP_REVIVED) {
fp->fp_flags &= ~FP_REVIVED;
reviving--;
wasreviving = 1;
}
switch (blocked_on) {
case FP_BLOCKED_ON_PIPE:/* process trying to read or write a pipe */
/* If the operation succeeded partially, return the bytes
* processed so far, and clear the remembered state. Otherwise,
* return EINTR as usual.
*/
if (fp->fp_cum_io_partial > 0) {
status = fp->fp_cum_io_partial;
fp->fp_cum_io_partial = 0;
}
break;
case FP_BLOCKED_ON_LOCK:/* process trying to set a lock with FCNTL */
break;
case FP_BLOCKED_ON_SELECT:/* process blocking on select() */
select_forget();
break;
case FP_BLOCKED_ON_POPEN: /* process trying to open a fifo */
break;
case FP_BLOCKED_ON_OTHER:/* process trying to do device I/O (e.g. tty)*/
fild = scratch(fp).file.fd_nr;
if (fild < 0 || fild >= OPEN_MAX)
panic("file descriptor out-of-range");
f = fp->fp_filp[fild];
if(!f) {
sys_diagctl_stacktrace(fp->fp_endpoint);
panic("process %d blocked on empty fd %d",
fp->fp_endpoint, fild);
}
dev = f->filp_vno->v_sdev; /* device hung on */
status = cdev_cancel(dev);
break;
default :
panic("VFS: unknown block reason: %d", blocked_on);
}
if ((blocked_on == FP_BLOCKED_ON_PIPE || blocked_on == FP_BLOCKED_ON_POPEN)&&
!wasreviving) {
susp_count--;
}
replycode(fp->fp_endpoint, status); /* signal interrupted call */
}