minix3/servers/vfs/filedes.c

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2020-02-21 00:59:27 +05:30
/* This file contains the procedures that manipulate file descriptors.
*
* The entry points into this file are
* get_fd: look for free file descriptor and free filp slots
* get_filp: look up the filp entry for a given file descriptor
* find_filp: find a filp slot that points to a given vnode
* inval_filp: invalidate a filp and associated fd's, only let close()
* happen on it
* do_copyfd: copies a file descriptor from or to another endpoint
*/
#include <sys/select.h>
#include <minix/callnr.h>
#include <minix/u64.h>
#include <assert.h>
#include <sys/stat.h>
#include "fs.h"
#include "file.h"
#include "vnode.h"
#if LOCK_DEBUG
/*===========================================================================*
* check_filp_locks *
*===========================================================================*/
void check_filp_locks_by_me(void)
{
/* Check whether this thread still has filp locks held */
struct filp *f;
int r;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
r = mutex_trylock(&f->filp_lock);
if (r == -EDEADLK)
panic("Thread %d still holds filp lock on filp %p call_nr=%d\n",
mthread_self(), f, job_call_nr);
else if (r == 0) {
/* We just obtained the lock, release it */
mutex_unlock(&f->filp_lock);
}
}
}
#endif
/*===========================================================================*
* check_filp_locks *
*===========================================================================*/
void check_filp_locks(void)
{
struct filp *f;
int r, count = 0;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
r = mutex_trylock(&f->filp_lock);
if (r == -EBUSY) {
/* Mutex is still locked */
count++;
} else if (r == 0) {
/* We just obtained a lock, don't want it */
mutex_unlock(&f->filp_lock);
} else
panic("filp_lock weird state");
}
if (count) panic("locked filps");
#if 0
else printf("check_filp_locks OK\n");
#endif
}
/*===========================================================================*
* init_filps *
*===========================================================================*/
void init_filps(void)
{
/* Initialize filps */
struct filp *f;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (mutex_init(&f->filp_lock, NULL) != 0)
panic("Failed to initialize filp mutex");
}
}
/*===========================================================================*
* get_fd *
*===========================================================================*/
int get_fd(struct fproc *rfp, int start, mode_t bits, int *k, struct filp **fpt)
{
/* Look for a free file descriptor and a free filp slot. Fill in the mode word
* in the latter, but don't claim either one yet, since the open() or creat()
* may yet fail.
*/
register struct filp *f;
register int i;
/* Search the fproc fp_filp table for a free file descriptor. */
for (i = start; i < OPEN_MAX; i++) {
if (rfp->fp_filp[i] == NULL) {
/* A file descriptor has been located. */
*k = i;
break;
}
}
/* Check to see if a file descriptor has been found. */
if (i >= OPEN_MAX) return(EMFILE);
/* If we don't care about a filp, return now */
if (fpt == NULL) return(OK);
/* Now that a file descriptor has been found, look for a free filp slot. */
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
assert(f->filp_count >= 0);
if (f->filp_count == 0 && mutex_trylock(&f->filp_lock) == 0) {
f->filp_mode = bits;
f->filp_pos = 0;
f->filp_selectors = 0;
f->filp_select_ops = 0;
f->filp_pipe_select_ops = 0;
f->filp_char_select_dev = NO_DEV;
f->filp_flags = 0;
f->filp_select_flags = 0;
f->filp_softlock = NULL;
f->filp_ioctl_fp = NULL;
*fpt = f;
return(OK);
}
}
/* If control passes here, the filp table must be full. Report that back. */
return(ENFILE);
}
/*===========================================================================*
* get_filp *
*===========================================================================*/
struct filp *get_filp(fild, locktype)
int fild; /* file descriptor */
tll_access_t locktype;
{
/* See if 'fild' refers to a valid file descr. If so, return its filp ptr. */
return get_filp2(fp, fild, locktype);
}
/*===========================================================================*
* get_filp2 *
*===========================================================================*/
struct filp *get_filp2(rfp, fild, locktype)
register struct fproc *rfp;
int fild; /* file descriptor */
tll_access_t locktype;
{
/* See if 'fild' refers to a valid file descr. If so, return its filp ptr. */
struct filp *filp;
filp = NULL;
if (fild < 0 || fild >= OPEN_MAX)
err_code = EBADF;
else if (locktype != VNODE_OPCL && rfp->fp_filp[fild] != NULL &&
rfp->fp_filp[fild]->filp_mode == FILP_CLOSED)
err_code = EIO; /* disallow all use except close(2) */
else if ((filp = rfp->fp_filp[fild]) == NULL)
err_code = EBADF;
else if (locktype != VNODE_NONE) /* Only lock the filp if requested */
lock_filp(filp, locktype); /* All is fine */
return(filp); /* may also be NULL */
}
/*===========================================================================*
* find_filp *
*===========================================================================*/
struct filp *find_filp(struct vnode *vp, mode_t bits)
{
/* Find a filp slot that refers to the vnode 'vp' in a way as described
* by the mode bit 'bits'. Used for determining whether somebody is still
* interested in either end of a pipe. Also used when opening a FIFO to
* find partners to share a filp field with (to shared the file position).
* Like 'get_fd' it performs its job by linear search through the filp table.
*/
struct filp *f;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (f->filp_count != 0 && f->filp_vno == vp && (f->filp_mode & bits)) {
return(f);
}
}
/* If control passes here, the filp wasn't there. Report that back. */
return(NULL);
}
/*===========================================================================*
* invalidate_filp *
*===========================================================================*/
void invalidate_filp(struct filp *rfilp)
{
/* Invalidate filp. */
rfilp->filp_mode = FILP_CLOSED;
}
/*===========================================================================*
* invalidate_filp_by_char_major *
*===========================================================================*/
void invalidate_filp_by_char_major(devmajor_t major)
{
struct filp *f;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (f->filp_count != 0 && f->filp_vno != NULL) {
if (major(f->filp_vno->v_sdev) == major &&
S_ISCHR(f->filp_vno->v_mode)) {
invalidate_filp(f);
}
}
}
}
/*===========================================================================*
* invalidate_filp_by_endpt *
*===========================================================================*/
void invalidate_filp_by_endpt(endpoint_t proc_e)
{
struct filp *f;
for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (f->filp_count != 0 && f->filp_vno != NULL) {
if (f->filp_vno->v_fs_e == proc_e)
invalidate_filp(f);
}
}
}
/*===========================================================================*
* lock_filp *
*===========================================================================*/
void lock_filp(filp, locktype)
struct filp *filp;
tll_access_t locktype;
{
struct worker_thread *org_self;
struct vnode *vp;
assert(filp->filp_count > 0);
vp = filp->filp_vno;
assert(vp != NULL);
/* Lock vnode only if we haven't already locked it. If already locked by us,
* we're allowed to have one additional 'soft' lock. */
if (tll_locked_by_me(&vp->v_lock)) {
assert(filp->filp_softlock == NULL);
filp->filp_softlock = fp;
} else {
/* We have to make an exception for vnodes belonging to pipes. Even
* read(2) operations on pipes change the vnode and therefore require
* exclusive access.
*/
if (S_ISFIFO(vp->v_mode) && locktype == VNODE_READ)
locktype = VNODE_WRITE;
lock_vnode(vp, locktype);
}
assert(vp->v_ref_count > 0); /* vnode still in use? */
assert(filp->filp_vno == vp); /* vnode still what we think it is? */
/* First try to get filp lock right off the bat */
if (mutex_trylock(&filp->filp_lock) != 0) {
/* Already in use, let's wait for our turn */
org_self = worker_suspend();
if (mutex_lock(&filp->filp_lock) != 0)
panic("unable to obtain lock on filp");
worker_resume(org_self);
}
}
/*===========================================================================*
* unlock_filp *
*===========================================================================*/
void unlock_filp(filp)
struct filp *filp;
{
/* If this filp holds a soft lock on the vnode, we must be the owner */
if (filp->filp_softlock != NULL)
assert(filp->filp_softlock == fp);
if (filp->filp_count > 0) {
/* Only unlock vnode if filp is still in use */
/* and if we don't hold a soft lock */
if (filp->filp_softlock == NULL) {
assert(tll_islocked(&(filp->filp_vno->v_lock)));
unlock_vnode(filp->filp_vno);
}
}
filp->filp_softlock = NULL;
if (mutex_unlock(&filp->filp_lock) != 0)
panic("unable to release lock on filp");
}
/*===========================================================================*
* unlock_filps *
*===========================================================================*/
void unlock_filps(filp1, filp2)
struct filp *filp1;
struct filp *filp2;
{
/* Unlock two filps that are tied to the same vnode. As a thread can lock a
* vnode only once, unlocking the vnode twice would result in an error. */
/* No NULL pointers and not equal */
assert(filp1);
assert(filp2);
assert(filp1 != filp2);
/* Must be tied to the same vnode and not NULL */
assert(filp1->filp_vno == filp2->filp_vno);
assert(filp1->filp_vno != NULL);
if (filp1->filp_count > 0 && filp2->filp_count > 0) {
/* Only unlock vnode if filps are still in use */
unlock_vnode(filp1->filp_vno);
}
filp1->filp_softlock = NULL;
filp2->filp_softlock = NULL;
if (mutex_unlock(&filp2->filp_lock) != 0)
panic("unable to release filp lock on filp2");
if (mutex_unlock(&filp1->filp_lock) != 0)
panic("unable to release filp lock on filp1");
}
/*===========================================================================*
* close_filp *
*===========================================================================*/
void close_filp(f)
struct filp *f;
{
/* Close a file. Will also unlock filp when done */
int rw;
dev_t dev;
struct vnode *vp;
/* Must be locked */
assert(mutex_trylock(&f->filp_lock) == -EDEADLK);
assert(tll_islocked(&f->filp_vno->v_lock));
vp = f->filp_vno;
if (f->filp_count - 1 == 0 && f->filp_mode != FILP_CLOSED) {
/* Check to see if the file is special. */
if (S_ISCHR(vp->v_mode) || S_ISBLK(vp->v_mode)) {
dev = vp->v_sdev;
if (S_ISBLK(vp->v_mode)) {
lock_bsf();
if (vp->v_bfs_e == ROOT_FS_E) {
/* Invalidate the cache unless the special is
* mounted. Assume that the root filesystem's
* is open only for fsck.
*/
req_flush(vp->v_bfs_e, dev);
}
unlock_bsf();
(void) bdev_close(dev); /* Ignore errors */
} else {
(void) cdev_close(dev); /* Ignore errors */
}
f->filp_mode = FILP_CLOSED;
}
}
/* If the inode being closed is a pipe, release everyone hanging on it. */
if (S_ISFIFO(vp->v_mode)) {
rw = (f->filp_mode & R_BIT ? VFS_WRITE : VFS_READ);
release(vp, rw, susp_count);
}
if (--f->filp_count == 0) {
if (S_ISFIFO(vp->v_mode)) {
/* Last reader or writer is going. Tell PFS about latest
* pipe size.
*/
truncate_vnode(vp, vp->v_size);
}
unlock_vnode(f->filp_vno);
put_vnode(f->filp_vno);
f->filp_vno = NULL;
f->filp_mode = FILP_CLOSED;
f->filp_count = 0;
} else if (f->filp_count < 0) {
panic("VFS: invalid filp count: %d ino %llx/%llu", f->filp_count,
vp->v_dev, vp->v_inode_nr);
} else {
unlock_vnode(f->filp_vno);
}
mutex_unlock(&f->filp_lock);
}
/*===========================================================================*
* do_copyfd *
*===========================================================================*/
int do_copyfd(void)
{
/* Copy a file descriptor between processes, or close a remote file descriptor.
* This call is used as back-call by device drivers (UDS, VND), and is expected
* to be used in response to an IOCTL to such device drivers.
*/
struct fproc *rfp;
struct filp *rfilp;
endpoint_t endpt;
int r, fd, what, slot;
/* This should be replaced with an ACL check. */
if (!super_user) return(EPERM);
endpt = job_m_in.m_lsys_vfs_copyfd.endpt;
fd = job_m_in.m_lsys_vfs_copyfd.fd;
what = job_m_in.m_lsys_vfs_copyfd.what;
if (isokendpt(endpt, &slot) != OK) return(EINVAL);
rfp = &fproc[slot];
/* FIXME: we should now check that the user process is indeed blocked on an
* IOCTL call, so that we can safely mess with its file descriptors. We
* currently do not have the necessary state to verify this, so we assume
* that the call is always used in the right way.
*/
/* Depending on the operation, get the file descriptor from the caller or the
* user process. Do not lock the filp yet: we first need to make sure that
* locking it will not result in a deadlock.
*/
rfilp = get_filp2((what == COPYFD_TO) ? fp : rfp, fd, VNODE_NONE);
if (rfilp == NULL)
return(err_code);
/* If the filp is involved in an IOCTL by the user process, locking the filp
* here would result in a deadlock. This would happen if a user process
* passes in the file descriptor to the device node on which it is performing
* the IOCTL. We do not allow manipulation of such device nodes. In
* practice, this only applies to block-special files (and thus VND), because
* character-special files (as used by UDS) are unlocked during the IOCTL.
*/
if (rfilp->filp_ioctl_fp == rfp)
return(EBADF);
/* Now we can safely lock the filp, copy or close it, and unlock it again. */
lock_filp(rfilp, VNODE_READ);
switch (what) {
case COPYFD_FROM:
rfp = fp;
/* FALLTHROUGH */
case COPYFD_TO:
/* Find a free file descriptor slot in the local or remote process. */
for (fd = 0; fd < OPEN_MAX; fd++)
if (rfp->fp_filp[fd] == NULL)
break;
/* If found, fill the slot and return the slot number. */
if (fd < OPEN_MAX) {
rfp->fp_filp[fd] = rfilp;
rfilp->filp_count++;
r = fd;
} else
r = EMFILE;
break;
case COPYFD_CLOSE:
/* This should be used ONLY to revert a successful copy-to operation,
* and assumes that the filp is still in use by the caller as well.
*/
if (rfilp->filp_count > 1) {
rfilp->filp_count--;
rfp->fp_filp[fd] = NULL;
r = OK;
} else
r = EBADF;
break;
default:
r = EINVAL;
}
unlock_filp(rfilp);
return(r);
}