minix/servers/vfs/read.c
2009-05-07 09:57:43 +00:00

381 lines
9.4 KiB
C

/* This file contains the heart of the mechanism used to read (and write)
* files. Read and write requests are split up into chunks that do not cross
* block boundaries. Each chunk is then processed in turn. Reads on special
* files are also detected and handled.
*
* The entry points into this file are
* do_read: perform the READ system call by calling read_write
* do_getdents: read entries from a directory (GETDENTS)
* read_write: actually do the work of READ and WRITE
*
* Changes for VFS:
* Jul 2006 (Balazs Gerofi)
*/
#include "fs.h"
#include <fcntl.h>
#include <unistd.h>
#include <minix/com.h>
#include <minix/u64.h>
#include "file.h"
#include "fproc.h"
#include "param.h"
#include <dirent.h>
#include <assert.h>
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
/*===========================================================================*
* do_read *
*===========================================================================*/
PUBLIC int do_read()
{
return(read_write(READING));
}
/*===========================================================================*
* read_write *
*===========================================================================*/
PUBLIC int read_write(rw_flag)
int rw_flag; /* READING or WRITING */
{
/* Perform read(fd, buffer, nbytes) or write(fd, buffer, nbytes) call. */
register struct filp *f;
register struct vnode *vp;
off_t bytes_left;
u64_t position, res_pos, new_pos;
unsigned int off, cum_io, cum_io_incr, res_cum_io, num_of_bytes;
int op, oflags, r, chunk, usr, block_spec, char_spec;
int regular;
mode_t mode_word;
phys_bytes p;
struct dmap *dp;
/* PM loads segments by putting funny things in other bits of the
* message, indicated by a high bit in fd. */
if (who_e == PM_PROC_NR && (m_in.fd & _PM_SEG_FLAG)) {
panic(__FILE__,
"read_write: special read/write calls by PM no longer supported",
NO_NUM);
}
else {
usr = who_e; /* normal case */
}
/* If the file descriptor is valid, get the vnode, size and mode. */
if (m_in.nbytes < 0)
return(EINVAL);
if ((f = get_filp(m_in.fd)) == NIL_FILP) {
return(err_code);
}
if (((f->filp_mode) & (rw_flag == READING ? R_BIT : W_BIT)) == 0) {
#if 0
printf("vfs:read_write: returning error\n");
#endif
return(f->filp_mode == FILP_CLOSED ? EIO : EBADF);
}
if (m_in.nbytes == 0)
return(0); /* so char special files need not check for 0*/
position = f->filp_pos;
oflags = f->filp_flags;
vp = f->filp_vno;
if (vp->v_pipe)
{
if (fp->fp_cum_io_partial != 0)
{
panic(__FILE__, "read_write: fp_cum_io_partial not clear",
NO_NUM);
}
return rw_pipe(rw_flag, usr, m_in.fd, f, m_in.buffer, m_in.nbytes);
}
r = OK;
cum_io = 0;
op = (rw_flag == READING ? VFS_DEV_READ : VFS_DEV_WRITE);
mode_word = vp->v_mode & I_TYPE;
regular = mode_word == I_REGULAR;
if ((char_spec = (mode_word == I_CHAR_SPECIAL ? 1 : 0))) {
if (vp->v_sdev == NO_DEV)
panic(__FILE__,"read_write tries to read from "
"character device NO_DEV", NO_NUM);
}
if ((block_spec = (mode_word == I_BLOCK_SPECIAL ? 1 : 0))) {
if (vp->v_sdev == NO_DEV)
panic(__FILE__,"read_write tries to read from "
" block device NO_DEV", NO_NUM);
}
/* Character special files. */
if (char_spec) {
dev_t dev;
int suspend_reopen;
suspend_reopen= (f->filp_state != FS_NORMAL);
dev = (dev_t) vp->v_sdev;
r = dev_io(op, dev, usr, m_in.buffer, position, m_in.nbytes, oflags,
suspend_reopen);
if (r >= 0) {
cum_io = r;
position = add64ul(position, r);
r = OK;
}
}
/* Block special files. */
else if (block_spec) {
/* Issue request */
r = req_breadwrite(vp->v_bfs_e, usr, vp->v_sdev, position,
m_in.nbytes, m_in.buffer, rw_flag, &res_pos, &res_cum_io);
position = res_pos;
cum_io += res_cum_io;
}
/* Regular files */
else {
if (rw_flag == WRITING && block_spec == 0) {
/* Check for O_APPEND flag. */
if (oflags & O_APPEND) position = cvul64(vp->v_size);
}
/* Fill in request structure */
num_of_bytes = m_in.nbytes;
#if 0 /* Don't truncate read request at size. The filesystem process will
* do this itself.
*/
if((rw_flag == READING) &&
cmp64ul(add64ul(position, num_of_bytes), vp->v_size) > 0) {
/* Position always should fit in an off_t (LONG_MAX). */
off_t pos32;
assert(cmp64ul(position, LONG_MAX) <= 0);
pos32 = cv64ul(position);
assert(pos32 >= 0);
assert(pos32 <= LONG_MAX);
num_of_bytes = vp->v_size - pos32;
assert(num_of_bytes >= 0);
}
#endif
/* Issue request */
r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, vp->v_index, position,
rw_flag, usr, m_in.buffer, num_of_bytes, &new_pos, &cum_io_incr);
if (r >= 0)
{
if (ex64hi(new_pos))
panic(__FILE__, "read_write: bad new pos", NO_NUM);
position = new_pos;
cum_io += cum_io_incr;
}
}
/* On write, update file size and access time. */
if (rw_flag == WRITING) {
if (regular || mode_word == I_DIRECTORY) {
if (cmp64ul(position, vp->v_size) > 0)
{
if (ex64hi(position) != 0)
{
panic(__FILE__,
"read_write: file size too big for v_size",
NO_NUM);
}
vp->v_size = ex64lo(position);
}
}
}
f->filp_pos = position;
if (r == OK) {
return cum_io;
}
return r;
}
/*===========================================================================*
* do_getdents *
*===========================================================================*/
PUBLIC int do_getdents()
{
/* Perform the getdents(fd, buf, size) system call. */
int r;
off_t pos_change;
cp_grant_id_t gid;
register struct filp *rfilp;
/* Is the file descriptor valid? */
if ( (rfilp = get_filp(m_in.fd)) == NIL_FILP) {
return(err_code);
}
if (!(rfilp->filp_mode & R_BIT))
return EBADF;
if ((rfilp->filp_vno->v_mode & I_TYPE) != I_DIRECTORY)
return EBADF;
gid=cpf_grant_magic(rfilp->filp_vno->v_fs_e, who_e, (vir_bytes) m_in.buffer,
m_in.nbytes, CPF_WRITE);
if (gid < 0) panic(__FILE__, "cpf_grant_magic failed", gid);
/* Issue request */
if (ex64hi(rfilp->filp_pos) != 0)
panic(__FILE__, "do_getdents: should handle large offsets", NO_NUM);
r= req_getdents(rfilp->filp_vno->v_fs_e, rfilp->filp_vno->v_inode_nr,
ex64lo(rfilp->filp_pos), gid, m_in.nbytes, &pos_change);
cpf_revoke(gid);
if (r > 0)
rfilp->filp_pos= add64ul(rfilp->filp_pos, pos_change);
return r;
}
/*===========================================================================*
* rw_pipe *
*===========================================================================*/
PUBLIC int rw_pipe(rw_flag, usr, fd_nr, f, buf, req_size)
int rw_flag; /* READING or WRITING */
endpoint_t usr;
int fd_nr;
struct filp *f;
char *buf;
size_t req_size;
{
int r, oflags, op, partial_pipe;
size_t size, cum_io, cum_io_incr;
struct vnode *vp;
u64_t position, new_pos;
oflags = f->filp_flags;
vp = f->filp_vno;
position = cvu64((rw_flag == READING) ? vp->v_pipe_rd_pos :
vp->v_pipe_wr_pos);
#if 0
printf("vfs:rw_pipe: filp 0x%x pipe %s, buf 0x%x, size %d\n",
f, rw_flag == READING ? "read" : "write", buf, req_size);
printf("vfs:rw_pipe: pipe vp 0x%x, dev/num 0x%x/%d size %d, pos 0x%x:%08x\n",
vp, vp->v_dev, vp->v_inode_nr,
vp->v_size, ex64hi(position), ex64lo(position));
#endif
/* fp->fp_cum_io_partial is only nonzero when doing partial writes */
cum_io = fp->fp_cum_io_partial;
op = (rw_flag == READING ? VFS_DEV_READ : VFS_DEV_WRITE);
r = Xpipe_check(vp, rw_flag, oflags, req_size, position, 0);
if (r <= 0)
{
if (r == SUSPEND)
pipe_suspend(rw_flag, fd_nr, buf, req_size);
return(r);
}
size = r;
if (r < req_size)
partial_pipe = 1;
else
partial_pipe = 0;
/* Truncate read request at size. */
if((rw_flag == READING) &&
cmp64ul(add64ul(position, size), vp->v_size) > 0) {
/* Position always should fit in an off_t (LONG_MAX). */
off_t pos32;
assert(cmp64ul(position, LONG_MAX) <= 0);
pos32 = cv64ul(position);
assert(pos32 >= 0);
assert(pos32 <= LONG_MAX);
size = vp->v_size - pos32;
}
/* Issue request */
r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, vp->v_index, position,
rw_flag, usr, buf, size, &new_pos, &cum_io_incr);
if (r >= 0)
{
if (ex64hi(new_pos))
panic(__FILE__, "read_write: bad new pos", NO_NUM);
position = new_pos;
cum_io += cum_io_incr;
buf += cum_io_incr;
req_size -= cum_io_incr;
}
/* On write, update file size and access time. */
if (rw_flag == WRITING) {
if (cmp64ul(position, vp->v_size) > 0)
{
if (ex64hi(position) != 0)
{
panic(__FILE__,
"read_write: file size too big for v_size",
NO_NUM);
}
vp->v_size = ex64lo(position);
}
}
else {
if (cmp64ul(position, vp->v_size) >= 0) {
/* Reset pipe pointers */
#if 0
printf("vfs:rw_pipe: resetting pipe size/positions\n");
#endif
vp->v_size = 0;
vp->v_pipe_rd_pos= 0;
vp->v_pipe_wr_pos= 0;
position = cvu64(0);
}
}
if (rw_flag == READING)
vp->v_pipe_rd_pos= cv64ul(position);
else
vp->v_pipe_wr_pos= cv64ul(position);
if (r == OK) {
if (partial_pipe) {
/* partial write on pipe with */
/* O_NONBLOCK, return write count */
if (!(oflags & O_NONBLOCK)) {
/* partial write on pipe with req_size > PIPE_SIZE,
* non-atomic
*/
fp->fp_cum_io_partial = cum_io;
pipe_suspend(rw_flag, fd_nr, buf, req_size);
return(SUSPEND);
}
}
fp->fp_cum_io_partial = 0;
return cum_io;
}
return r;
}